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BIOMECHANICS of the hind
limb of HORSE and DOG
G.H. Wentink
design: H.Schifferstein
Institute of Veterinary Anatomy, State University, UtrechJ, The Netherlands
1. Tensor fasciae latae
2. Gluteus medius
3. cranial hamstrings (parts of the
biceps femoris and semimembranosus
inserting on the thigh)
4. caudal hamstrings (parts of the
biceps femoris and semimembranosus
inserting on the shank and the
semitendinosus)
5. Tibial is cranialis
6.  (horse) Peroneus tertius
(dog) Peroneus longus
7.  Extensor digitorum longus
8.  Rectus femoris
9. Vastus lateralis
10. Gastrocnemius
11.  Flexor digitorum superficialis
12. Flexor digitorum profundus
13.  Interosseus
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Biomechanics of the hind limb of
the horse and dog
Proefschrift
ter verkrijging van de graad van doctor in de
diergeneeskunde aan de Rijksuniversiteit te Utrecht,
op gezag van de Rector Magnificus Prof. Dr. A. Verhoeff,
volgens besluit van het College van Decanen in het
openbaar te verdedigen op donderdag 8 juni 1978
des namiddags te 4.15 uur
door
Gerrit Hendrik Wentink
geboren op 6 januari 1945
te Zelhem                                                     , , ,
Bibliotheek der
rTmuTgECHT                    „lijksiKÜversiteit te Utrecht
Afd. Diergeneeskunde
1467 9157
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Promotoren: Dr. D.M. Badoux
Prof. Dr. A. Huson (Rijksuniversiteit Leiden)
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Aan de nagedachtenis aan mijn vader
Aan mijn moeder
Aan Ineke, Esther en Robbert
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CONTENTS
Voorwoord
Introduction
The action of the hind limb musculature of
the dog in walking
Acta Anat. 96, 70-80 (1976)
Biokinetical analysis of hind limb
movements of the dog
Anat. Embryol. 151, 171-181 (1977)
Biokinetical analysis of the movements
of the pelvic limb of the horse and the
role of the muscles in the walk and the
trot
Anat. Embryol. 152, 261-272 (1978)
Dynamics of the hind limb at walk in
horse and dog
Anat. Embryol. (in press)
An experimental study on the role of the
reciprocal tendinous apparatus of the
horse at walk
Anat. Embryol. (submitted)
Biomechanics of the hind limb of horse
and dog. Synopsis
Summary
Samenvatting
Curriculum vitae
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VOORWOORD
Aan dit onderzoek hebben vele mensen meegewerkt; ik
denk aan de samenwerking met hen met genoegen terug en ik
breng hierbij mijn oprechte dank uit voor hun inzet. Op
deze pagina kan ik slechts enkelen vermelden.
In de eerste plaats wil ik Dr. D.M. Badoux en Prof.
Dr. A. Huson noemen. Dr. Badoux heeft mijn belangstelling
voor mechanische aspekten van de voortbeweging gewekt;
deze belangstelling heeft geresulteerd in dit proefschrift
dat hoofdzakelijk onder zijn leiding tot stand kwam. Bij
de interpretatie zijn de suggesties en opbouwende kritiek
van Prof. Huson van even grote betekenis geweest.
Dank ben ik ook verschuldigd aan Professor Dr.K.M. Dyce
die een belangrijk aandeel heeft gehad bij de voorbereiding
van de definitieve versie van de manuskripten.
Met grote waardering denk ik terug aan de vruchtbare
diskussies die ik tijdens de uitvoering van dit onderzoek
heb gevoerd met Ir. C.W. Spoor, Dr. P.L. Lijnse en
Dr. W. Hartman.
Zonder de technische assistentie van de heren
C.J. Slieker (electromyografie), M. Klein en Chr. van
Nieuwenhuisen (film), en van Drs. J.S.M.M, van Dieten
(experimentele chirurgie) was dit onderzoek onmogelijk
geweest. De inbreng van de heren J.G. Nokkert, P.W. Hocgeveen
en G.W. Hol, en van mej. A.C. Rosweide heb ik hogelijk op prijs
gesteld. De technische faciliteiten die ter beschikking
werden gesteld door Prof. Dr. G.H. Huisman en Dr. J. Kroneman
hebben belangrijk bijgedragen tot een vlot verloop van dit
onderzoek.
De vormgeving van dit proefschrift is tot stand gekomen
onder leiding van de heren H.H. Otter en H. Schifferstein:
een woord van dank alleen is eigenlijk onvoldoende voor hun
bijdrage.
De manuskripten zijn drukklaar gemaakt door mevrouw
L.J.M. Michielsen-Pelders.
Bij deze gevoelens van dankbaarheid komt ook verwarring:
enerzijds is er de opluchting over de voltooing - om tot slot
van het werk het begin te schrijven lijkt het einde - ander-
zijds komt er een verlangen naar meer. Immers, dit onderzoek
biedt mij een geweldig zicht op de biomechanica en betekent
daardoor in zekere zin pas een begin.
Op deze pagina hoort ook een verontschuldiging: Ineke,
Esther en Robbert, veel tijd waarop jullie recht hadden, zit
in de pagina's van dit proefschrift, en dat tekort kan ik
met de opdracht alleen niet rechttrekken.
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voer
CMKa/l
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INTRODUCTION
An Arabian proverb says that paradise on earth is to
be found on the back of a horse, in the pages of a book
and in the arms of a woman.
Hence, writing a booklet on horses would be a pleasant
task, were it not that the publication of a monograph
intended to explain some mechanical aspects of the
horse's locomotion is in fact an hazardous undertaking.
This is the more so since many scientists have dealt
with the subject to which the present study is only a
modest contribution.
The more general literature of animal locomotion is
exhaustive but often rather superficial and attention
will be focused on the records of equine locomotion.
One may appropriately begin with the work of Hayes,
which was published in 1893. Hayes considered the.
relation between the conformation of a horse and its
physical capabilities. He analyzed the aptness of
horses for draught, speed and endurance by comparison
of their external conformation with that of other
animal species with pronounced locomotor abilities.
In his evaluation of the external features of the limbs
with respect to their task, he left out of consideration
the function of the intrinsic muscles and tendons. About
70 years later, Adams (1966) also contents himself with
a purely verbal record of the movements of the limbs;
he derived the function of the muscles and tendons, as
well as the sequence of their activities in the moving
limb, from their points of origin and insertion.
The impetus for a pictorial survey of animal
locomotion was given by Muybridge, who in 1878 (see
Pearson, 1976) and in 1892 published photographic records
of moving horses. From this time, cinematography has
proven itself to be indispensable for the study of all
aspects of animal locomotion and in a sense it has
provided the basis of modern kinesiology. Footfall
patterns, angular changes in joints during locomotion,
the duration of the periods of ground contact and toe-off
as well as movements of parts of the body other than
limbs have been studied by cinerecords of moving animals
(Alexander, 1974, 1977; Fredericson, 1972; Gambaryan,
1974; Hildebrand, 1965, 1968; Manter, 1938; Muybridge,
1892).
It goes without saying that either a verbal or a
pictorial record, nor even a combination of both, is
7
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The aim of this study was primarily to describe the
movements of the hind limb at walk in relation with the
periods of muscular activity with emphasis upon the
role of the muscles located parallel with the tendons
of the crural reciprocal apparatus. The latter aspect
was a follow-up of a study by Badoux (1970), who
postulated that the crural muscles of the horse centre
the line of action of the load through the long axis of
the tibia. Badoux based his theory on the calculation
of the effect of the force developed by the gastrocnemius
muscle, counteracted by the peroneus tertius tendon in
a statical situation. During the progress of the present
study it became clear that the angular changes in stifle
and hoek joints in the horse were less strictly coupled
by the tendons of the reciprocal apparatus than could
be expected from the proper meaning of the term
"reciprocal", so that the study of the role of these
tendons as well as that of the muscles became of equal
importance. Although this study provides additional
evidence which supports the alledged role of the crural
muscles of the horse, it must be emphasized that the
question whether these muscles centre the load on the
tibia can only be answered by in vivo bone strain
measurements.
The study includes comparison of certain aspects of
the kinematics of the hind limb of the horse with that
of the dog, a species which lacks the reciprocal
tendinous apparatus; it also includes a comparison of
the kinematics of the hind limb of horses before and
after transection of the tendons of the reciprocal
apparatus.
II. METHODS
a) Introduction
Living and inanimate bodies are subject to the same
physical rules and therefore they obey the three fundamen-
tal Newtonian laws of motion. The first law states that
a body continues its state of rest or uniform rectilinear
motion unless it is compelled to change that state by
applied forces. The second law says that the change of
movement per unit of time is proportional to the applied
force and takes place in the direction of that force.
The third law states that forces always occur in pairs,
consisting of two equal opposites; in other words: for
9
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every action there must be a reaction. When a land
dweiling animal retracts its limb to push its body
forward, the ground reaction exerts an equal but
opposite background force against the foot (fig. l).
Figure 1
A. schematic representation of the forces exerted at the
right hip joint and at the feet.
F and F : the direction of the vertical and horizontal
componencs of the force exerted by the femoral head against
the acetabular wall.
F and F : the direction of the vertical and horizontal
componencs of the force exerted by the acetabular wall
against the femoral head.
2 and L: the direction of the vertical and horizontal
;omponents of the force exerted by the feet against the
ground.
T and W: the direction of the vertical and horizontal
:omponents of the force exerted by the ground against the
i:eet, normal reaction and friction respectively.
^11 forces occur in pairs of equal magnitude, but opposite
iirection (sense).
0
-ocr page 13-
The complicated structure of the animal locomotory
organs renders the evaluation of the direct and indirect
effects of intrinsic and extrinsic forces very difficult,
the more so since it is technically very difficult to
measure in vivo forces within the locomotor system. It
is common practice therefore to approach locomotor
problems by reducing the living structure to an
appropriate model which is more easily accessible to a
mechanical analysis.
b) Model of the hind limb
In this study a three-bar two-hinge mechanism
represents the basic structure of the hind limb (fig. 2);
the three bars are the thigh, shank and cannon (in the
dog metatarsus and digit) respectively, the hinge points
S\
A                                        B
Figure 2
The position of the markers on the skin over the skeletal
points indicated (A), and the model of the hind limb based
on these markers (B).
11
-ocr page 14-
the stifle and hoek joints. In this model the hinges
and the centres of gravity (centroids) of the bars are
well-defined points within geometrical bodies in which
the mass is evenly distributed. In the actual limb
however, the centroids of the segments shift due to
muscular contractions and the pivot points (hypomochlions)
of the joints alter their position in flexion and
extension. Hence, the animal body constitutes a more
complex structure witb a continuous change of its
mechanical state.
The biomechanical analysis of the model gives
information on the relative magnitude and sense of the
forces applied to the limb segments and the joints and
may therefore contribute to understanding of the
mechanical background of the processes of wear and tear
in the locomotory apparatus.
c) The moving animal
There is a wide variety in the patterns of
locomotion in animals. This study was focused primarily
on the walk, since a good part of it was carried out with
horses and dogs walking on a moving belt which hampers
studies of fast gaits.
Walk is a slow gait in which alternately two or three
feet are in contact with the ground; a limb is lifted
after replacement of its contralateral fellow. The cycle
of a stride commences when the limb is placed. The
support phase (i.e. the period in which the foot is in
contact with the ground) covers about 60 % of the cycle
of a stride, the remaining 40 % being consumed by the
rigure 3
schematic representation of the horse at walk.
i. The positions of the limbs in eight successive stages of
the walk.
1. The footfall pattern of the corresponding stages.
I. The periods of ground contact of the limbs are given in
horizontal black bars. The bars represent from top to
bottom the right hind limb, the right front limb, the left
hind limb and the left front limb. The period of the
support phases is about 60 % of the cycle of a stride.
2
-ocr page 15-
D
O
G
H
a
o
H
H
H
D
D
O
D
O H O D
O
-ocr page 16-
swing phase. The cycle is completed with replacement
of the limb. The sequence of the footfall pattern for
the normal walk may be presented 1. right hind limb,
2. right fore limb, 3. left hind limb, 4. left fore
limb, 5. right hind limb again. This pattern is found
in most quadrupedal animals (Hildebrand, 1963, 1968;
Pearson, 1976), although some prefer an ipsilateral
(laterally coupled) gait to the above described contra-
lateral (diagonally coupled) pattern. A schematic
representation of the walk is given in fig. 3.
cl) The support phase
During the support phase the (hind) limb has a
twofold task: a. it supports the body,i.e. it prevents
sagging by the action of its intrinsic muscles which by
fixing the hinges convert the mechanism into a strut
suited to oppose the forces applied at the proximal (hip)
and distal (foot) ends; b. it propels the body, i.e. it
acts as a lever and rotates hip and foot. From Newton's
third law it follows that the total action at the distal
end of the limb (i.e. the foot) against the ground
(which is the vectorial sum of the vertical weight and
the horizontal force due to muscular action) is counter-
acted by the total ground reaction (which in turn is the
vectorial sum of the vertical normal reaction and the
horizontal frictional force) (fig. 1). The magnitude
of the ground reactions has been measured in the dog
(Barclay, 1953; Kimura and Endo, 1972) and horse (Pratt
and Q'Connor, 1976). In the first part of the support
phase, the sense of friction is opposite to the
direction of progression and has a retarding (negative)
effect. In the last part of the support phase friction
and progression have the same (positive) sense (fig. 1).
The net effect of friction during the total support
phase of the hind limb is positive.
At the proximal end of the limb - the hip joint -
the partial body "weight is vertically transferred from
the acetabular roof to the femoral head and the forces
exerted by the other limbs in contact with the ground
are horizontally transferred from the acetabular wall to
the corresponding aspect of the femoral head. At
placing, this horizontal force has a sense in the
direction of progression; it is composed of the propulsive
force of the contralateral hind limb at the proper hip
joint and of inertia (see section d.), as follows from
4
-ocr page 17-
Newton's first law (fig. 1). In the middle of the
support phase the limb has to deal preponderantly with
the forces in the vertical direction acting at foot
and hip; friction is insignificant in this part of the
cycle. At the end of the support phase, the sense of
friction is positive and pushes the body forward; this
forward impulse, however, is counteracted at the hip by
the combined friction of the other hind limb in contact
with the ground and by the effect of inertia (see
section d.).
c2) The swing phase
During the swing phase the limb swings forward, its
joints are flexed, and its centre of gravity is brought
closer to the pivot point at the hip. This flexion
diminishes the distance r between pivot point and centre
of gravity of the whole limb and hence decreases the
moment of inertia (I = mr2).
At the end of the swing phase, the hind limb regains
its favourable position for the following support phase.
The biomechanical analysis of the hind limb describes
the action of the muscles which oppose the effects of the
above mentioned external forces.
d) Methods of calculation
The method by which the hind limb is divided into
segments, the determination of their mass and the position
of the centre of gravity (centroid), the pictorial
reconstruction of a complete cycle of a stride from the
cinematographical record and the determination of the
periods of muscular activity by electromyography are
amply described in the separate papers (1, 2, 3).
In the pictorial reconstructions, the travel of the
centroids was measured in three strides of every animal
(fig. 4). The stride pictured in an optimal cinemato-
graphical recording was chosen to approach speed and
acceleration.
The displacement (s) was measured in the horizontal
(X) and vertical (Y) directions. The speed (velocity)
v of the centroid of the limb segments in the middle of
the time interval initially chosen is the rate of
displacement in both directions (X and Y), hence
V = TT                                   (1)
SI units m.s
15
-ocr page 18-
Figure 4
The reconstruction of the cycle of a stride of two different
horses taken from the film. The black dots represent the
positions of the centres of gravity of the limb segments at
regular intervals during the cycle of a stride.
16
-ocr page 19-
The acceleration (a) is expressed as the rate of
change of velocity, hence
(2)
■2
SI units m.s
The analysis of the cinematographical record clearly
demonstrates that the change of speed per unit of time
of the centroid of a limb segment is unequal in
magnitude and direction, hence the acceleration is
variable.
The force (F) required to obtain the observed
acceleration follows from the product of the mass of the
segment and the acceleration:
F = m.a                                                              (3)
SI units Newton (N)
The force was calculated for the accelerations in
both directions (X and Y). The resultant force F is the
vectorial sum of Fy and F , and this is the force which
is required at the centre of gravity of the segment in
order to produce the rate of acceleration.
It must be kept in mind, however, that F is not identical
with the resultant F of all forces acting upon the
segment under consideration. This latter force F is
parallel with and equals F , but its point of application
lies at some distance from the centroid: its moment
induces a rotation of the segment around its centre of
gravity. The movement of two segments relative to each
other is expressed by the angular changes of the joints.
For every individual, these changes have been measured in
three strides; their average was taken as the starting
point for further calculations.
The average angular velocity (w) in the middle of the
time interval initially chosen is defined as the rate of
change of the joint angle (A 9) between two segments in
the time interval (At), and is an approximation of the
actual angular velocity:
At
SI units
rad. s
(4)
1
-ocr page 20-
The angular acceleration ( (3 ) is the rate of change
in the angular velocity of two segments with respect to
each other about their joint axis:
B= A"
At                                                            (5)
-2
SI units rad.s
The parameters referred to above enable to approach
the linear and angular acceleration and the required
forces at the centres of gravity. For descriptive
reasons, however, some remarks should be made about
moments, although these are not available. Generally
speaking, a moment which produces a given angular
acceleration (<x ) is the product of a and the moment of
inertia. It must be kept in mind, that a applies to
the angular acceleration of the axis of a segment with
respect to the one axis of an established coordinate
system, whereas 13 (5) refers to the angular acceleration
between two linked segments. Hence cannot be used for
calculations of a moment referred to above.
The mcvements of a segment are governed by F , which
is the resultant of gravitational force (applied at the
centre of gravity) and forces applied at the proximal and
distal ends of the segment. The position of the segment
in the kinematic chain determines the character of the
latter forces. In the case of an end link (foot), the
reactional force is the vectorial sum of the normal
reaction and friction at the distal end; the other
force at the proximal end incorporates the effect of
muscular forces. In any other link, the forces at the
ends comprise the effect of the muscular forces at both
ends.
In order to be able to calculate the forces at both
ends one has to know the numerical value of the
reactional forces, but for technical reasons set forth
above measurements of the ground reaction were impossible.
Therefore, the contribution of the muscles to the
movements of the limb was only estimated from the
vectorial direction of F , from the angular acceleration
B at the joints, and from the potential function
(based on origin and insertion) of the muscles which
display activity.
In the fourth paper the forces and moments which
eventually cause the movements of a segment are for pure
descriptive reasons lumped in two formulas:
-ocr page 21-
F = F„ + F _,_ + F                                          (6)
g n+w m
M + M + M + M + M.                               (7)
g n+w m 1
It must be kept in mind, that the effect of the reactional
F and M eventually depends for each segment on its
n+w . -n+w_ . . 1- v •
position in the kmematic chain.
In the latter formula M. denotes the moment of the
inertial force about the axis of the joint; its accele-
ration is equal in magnitude but opposite in direction
to the acceleration applied at the joint axis.
In the second, third and fourth paper, the force of
inertia has been interpreted as being substantially
equal but oppositely directed to the sum of the external
forces operant at the segments to allow a statical
approach (see fig. 5 in paper 4). From the standpoint
of theoretical physics, this procedure can be criticized.
The d'Alembert conception of Newtonian mechanics
essentially consists of regarding the mass-acceleration
product of Newton's second law (for an invariant mass)
as a "stop the motion" force, which permits a dynamics
problem to appear like a staties problem (Fanger, 1970).
This "stop the motion" force (or series of component
forces in the case of separate limb segments) is often
termed the reverse effective force or the inertia force
on the nass. It is exactly equal to,but oppositely
directed from the body m.a product. Were such a force
to be represented on the free body diagram by a vector
F = - ma, it would create an impression of static
equilibrium. It has been common to speak of the
d'Alembert principle as a means of creating dynamic
equilibrium. Indeed this is a confusing and paradoxical
terminology. If F were added to both members of the
second law equation, we would obtain:
F + F = ma + F = ma + (- ma) = 0 (8)
In the presence of such a force, the body motion would
be stopped and the problem would be amenable to statical
analysis. However, the factor of body acceleration
cannot be so easily evaded, as will be seen when one
replaces the F of the left member of the equation by its
equivalent
F - ma = 0                                                        (9)
1
-ocr page 22-
which appears as a pure manipulation of mathematics:
the inertia force is purely fictitious.
In spite of the above conclusions, however, the
d'Alembert principle not only played a significant role
in the historical development of dynamics but also
carries a considerable significance in the current
context of moving animals; it allows one to consider
the effects of forces on the limb and its segments in
a state of dynamic equilibrium.
e) Possible errors
The skeletal points which were indicated for the
cinerecords have been amply explained in the papers
(1, 2, 3). The skin over these parts was marked while
the animals were standing square and the animals were
then filmed in this position. From these pictures a
model of the skeletal parts of the limb was constructed;
this model was then carefully redrawn in the outline of
the hind limb of the walking animal on the successive
filmframes.
Since the determination of velocities and accelera-
tions was based upon an analysis of cinerecords,
possible sources of errors can be found in:
1) a discrepancy between the position of the markers
on the skin with respect to the underlying bony
structures. This may lead to misinterpretation in the
reconstruction of the model of the hind limb.
2) inaccuracies in the measurements at the pictorial
reconstruction of the cycle of a stride, which may lead
to errors in the calculations of the linear and angular
accelerations.
The attention was primarily focused upon the
relation between the displacements of the centres of
gravity of the three segments and the relation between
the changes in the angles of the joints during a stride.
In normal animals, these relations were fairly constant
(fig. 4), although differences between consecutive
strides of a single animal and between various individuals
occurred.
ad 1) The greatest variation of the markers on the
skin was observed on the thigh: the caudal part of the
greater trochanter measures about 6 cm; hence the absolute
error is 3 cm. At the distal end of the femur the absolute
error is 2 cm. In the reconstruction of the model thus
a possible relative error of 12 percent in the length of
-ocr page 23-
the femur, and of 6 percent in the position of the
centre of gravity of the thigh may exist. The deviation
of the markers indicating the skeletal parts of the
tibia and the metatarsus was less due to the smaller
dimensions of these skeletal points (3 percent for both
tibia and metatarsus). This inaccuracy in the positions
of the markers leads to a relative error in the
determination of the actual angle of the stifle of about
10 percent, and of the hoek of about 6 percent. However,
in the reconstruction of a complete cycle of a stride
this error remains constant.
ad 2) The relative error in the measurements in the
reconstruction of the model is independent of the errors
mentioned under 1). For the displacements of the centres
of gravity this error is 5 percent, and for the angles of
the joints 7 percent.
f) Papers
The first paper describes the periods of activity of
the muscles of the hind limb of the dog.
The second paper gives kinematical and kinetical
characteristics of the hind limb of the dog.
The study was continued to determine the periods of
muscular activity of the muscles of the hind limb of the
horse, its kinematics and some aspects of its kinetics;
the results are described in the third paper.
In the fourth paper the kinematics of the hind limb
of the dog (digitigrade) and of the horse (unguligrade)
have been compared, and the consequences for the
locomotory abilities of both species are discussed.
The last paper describes the effect of experimental
surgery of the tendons of the reciprocal tendinous
apparatus and of the cranial tibial muscle on the
locomotor performance of the hind limb in horses
REFERENCES
Adams, O.R. : Lameness in horses. Philadelphia : Lea and
Febiger (2nd ed.) (1966).
Adrian, M.J.; Roy, W.E.; Karpovich, P.V. : Normal gait of the
dog : an electrogoniometric study. Amer. J. Vet. Res.
27, 90-95 (1966).
Alexander, R. McN. : The mechanics of jumping by a dog,
Canis familiaris. J. Zool., London 173, 549-573 (1974).
21
-ocr page 24-
Alexander, R. McN. : Allometry of the limbs of antelopes
(bovidae). J. Zool., London 183, 125-146 (1977).
Badoux, D,M. : The statical function of some crural muscles
in the horse. Acta Anat. 75, 396-407 (1970).
Barclay, O.R. : Some aspects of the mechanics of mammalian
locomotion. J. Exp. Biol. 30, 116-120 (1953).
Björk, G. : Studies on the draught force of horses. Acta
Agric. Scand., suppl. 4 (1958).
Dalin, G.; Drevemo, S.; Fredericson, I.; Jonsson, K.:
Ergonometric aspects of locomotor asymmetry in Standard
bred horses trotting through turns. Acta Vet. Scand.,
suppl. 44 (1973).
Engberg, J.; Lundberg, A. : An electromyographic analysis of
muscular activity in the hind limb of the cat during
unrestrained locomotion. Acta Physiol. Scand. 75,
614-630 (1969).
Fanger, C.G. : Engineering mechanics : staties and dynamics.
Columbus, Ohio : C.E. Merill Publishing Company (1970).
Fredericson, I.; Drevemo, S. : A photogrammetric method of
two-dimensional fast moving horses. Acta Vet. Scand.
suppl. 37 (1972).
Gambaryan, P.P. : How mammals run. New York, Toronto:
John Wiley and Sons (1974).
Hayes, M.H. : Points of the horse. London: Stanley Paul &
Co. Ltd., (7th reversed ed. 1969; first published 1893).
Hildebrand, M. : Symmetrical gaits of horses. Science 150,
701-708 (1965).
Hildebrand, M. : Symmetrical gaits of dogs in relation to
body build. J. Morphol. 124, 353-360 (1968).
Kimura, T.; Endo, B. : Comparison of force óf foot between
quadrupedal walking of dog and bipedal walking of man.
J. Fac. Sci. Tokyo 5, 119-130 (1972).
Lanyon, L.E.; Smith, R.N. : Bone strain in the tibia during
normal quadrupedal locomotion. Acta Orthop. Scand. 41,
238-248 (1970).
Manter, J.T. : The dynamics of quadrupedal locomotion.
J. Exp. Biol. 15, 522-540 (1938).
Muybridge, E. : Animals in motion. ed. L.S. Brown, New
York : Dover Publications (renewed ed. 1957, first
edition 1892).
Pearson, K. : The control of walking. Sci. Amer. 235,
72-87 (1976).
Pratt, G.W.; 0'Connor, J.T. : Force plate studies of equine
biomechanics. Amer. J. Vet. Res. 37, 1251-1255 (1976).
Rooney, J.R. : Biomechanics of lameness in horses. Baltimore:
Williams and Wilkins (1969).
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Rooney, J.R. : The lame horse. Cranbury, New Jersey :
Barnes & Co. (1975).
Rybicki, E.F.; Mills, E.J.; Turner, A.S.; Simonen, F.A. :
In vivo and analytical studies of forces and moments
in equine long bones. J. Biomech. 10, 701-705 (1977).
Taylor, B.M.; Tipton, C.M.; Adrian, M.; Karpovich, P.V. :
Action of certain joints in the legs of the horse
recorded electrogoniometrically. Amer. J. Vet. Res.
116, 85-89 (1966).
Tokuriki, M. : Electromyographic and joint-roechanical studies
in quadrupedal locomotion. I. Walk. Jap. J. Vet. Sci.
5, 433-446 (1973).
Turner, A.S.; Mills, E.J.; Gabel, A.A. : In vivo measurement
of bone strain in the horse. Amer. J. Vet. Res. 36,
1573-1579 (1975).
23
a.
-ocr page 26-
-ocr page 27-
Acta anat. 96: 70-80 (1976)
The action of the hind limb musculature of the dog in walking
G. H. Wentink
Institute of Anatomy, Veterinary Faculty, State University Utrecht,
Utrecht, The Netherlands
Key words. Locomotion • Muscles of hindlimb • Dog
Abstract. This study was performed by means of cinephotography and electromyography.
The results were correlated with earlier investigations concerning the forces exerted by the
pads of walking dogs. A concept about the action of individual muscles of the hind limb
during a stride was formed.
The principal conclusions are: (1) The hamstrings are divisible into a cranial and a
caudal group, the first consisting of the cranial parts of the M. biceps femoris and M. semi-
membranosus, the second of the caudal parts of these muscles, together with the M. semiten-
dinosus. The chief function of both groups is to extend the hip; the caudal group also flexes
the stifle. (2) Ac+ivity is present ir the greatest number of muscles during the change in the
sense of movement of the limb. (3) During the last stages of the stance phase the number of
muscles showing electrical activity diminishes, while the force exerted by the pads in a
horizontal direction increases. Non-muscular forces, e.g. inertia, play an important role
during movement.
Introduction
While there has been much research on the fundamental physiology of muscle, remarkably
little aitention has been paid to the actions and uses of individual muscles in natural circum-
stances. The actions conventionally ascribed to them are largely common-sense deductions
from their attachments, for which there is an almost total lack of experimental evidence.
Moreover, the authors of most Standard texts have been content to ascribe all movement to
muscular activity, to the neglect of other factors.
The purpose of the present paper is to confirm and extend the knowledge of the actions
of individual hind limb muscles of the dog during walking. Walk is defined as the slow gait
Received: August 18,1975.
25
-ocr page 28-
Wentink
in which two or three feet are alternately in contact with the ground and each foot is lifted
only after its contralateral fellow is replaced. It is recognized that there are variations in
the walk and individuals display a preference for a diagonal or lateral support, expressed
by differences in the relative durations of the periods when only two feet are in ground
contact. These differences proved to be irrelevant. In this study electromyography was
combined with cine-photography, a combination which reveals which muscles are active
during particular movements.
Several methods have been applied in earlier studies of canine locomotion. Hildebrand
[1968] recorded the walk on motion pictures and expressed it by means of a gait formula.
Adrian et al. [1966] measured the angular changes of the joints with electrogoniometers.
Barclay [1953] and Hutton et al. [1969] registered the forces exerted by the pads during
a normal stride. The electromyographic investigations of certain Japanese workers [No-
mura et al., 1966, Tokuriki, 1973] provide detailed information upon the sequence and
duration of activity of individual muscles in different gaits.
Material and methods
Five greyhounds with normal gaits were required to walk in an encaged 'trottoir roulant',
while being filmed from the right side at an exposure rate of 64 frames/sec. A switch attached
below the right metatarsal pad closed a circuit when compressed by a force exceeding 7 N
(this relatively small force is exceeded during almost the whole stance phase) [Barclay,
1953; Hutton et al., 1969]. Closure of the circuit was registered on the EMG tracé and also
illuminated a lamp within the picture field. The speed at which the trottoir was operated
determined the pattern of the walk and was adjusted to produce open and closed circuits
of equal duration. The average speed at which the dogs walked was 1,25 m-sec1 (4.5 km-h1).
The moment when the circuit was opened as the foot was about to be lifted from the ground
was chosen as the starting point of the step cycle. The cycle was divided into 22 stages,
corresponding to alternate frames of the film records. The interval between stages was thus
0.031 (2/64) sec.
The joint angles were measured for each stage of the cycle. They were determined by
measuring the angles enclosed by strips of adhesive tape extended between trochanter
major and lateral epicondyle of the femur, the lateral condyle and lateral malleolus of the
tibia, and the proximal and distal ends of the lateral metatarsal bone, all of which are easily
palpated. The ischial and coxal tuber were also marked. Since the skin is only slightly
movable over these skeletal parts, the angles measured give an acceptable indication of the
changes at the joints. The joint angles were measured over the fiexor aspects.
For the electromyographic investigation two platinum wire electrodes, from which
the insulation of the terminal 1-2 mm had been removed, were 'nserted in the middle of the
muscle belly. Electrical activity was assessed from the loudspeaker and monitor of a DISA
electromyograph type 14 A 30, and the signals registered on a Schwarzer carbon writer
(frequency response 75-350 Hz). No attempt was made to quantify theresponse: thepresence
or absence of muscular activity alone was noted.
26
-ocr page 29-
Wentink
Results and interpretation
The principal results are given in tabular form (fig. 1). The perpendicular
distance between trochanter major - and thus the acetabulum - and the ground
is least duting stages 0 and 11, when both hind pads have contact with the
ground; it is greatest in the middle of both stance and swing phases. The
acetabulum thus follows and undulating course in which the difference
between the highest and lowest points is 1,3 cm (in those dogs standing about
60 cm at the tuber coxae). There was no measurable horizontal displacement
of the trochanter major in relation to the cage, indicating a constant velocity
of the trunk. The distance between trochanter major and the distal end of
Mt 5 was taken as a measure of the functional length of the limb. This length
shortens from stages 0-6, increases thereafter to reach its maximum in stage
9 just before the paw makes contact with the ground. It shortens again in the
beginning of the stance phase when a lead of 7 N is accepted by the foot,
and remains almost constant during the whole stance phase (to 22). From
the film, conclusions can be made of movements in the sagittal plane alone
and the interpretation of muscle action is correspondingly restricted.
The changes in the joint angles scarcely need explanation. The changes
at the hip are out of phase with those at the stifle and hoek during most of the
cycle. Stifle and hoek follow approximately the same course; a difference
exists only in stages 1 and 2 and again in stages 10 and 11 when the foot is
lifted and replaced.
The deviation from the vertical of the axis of the femur varies between
0 and 40°. These extremes are attained in stage 1 when the leg is lifted and in
stage 8 shortly before the foo+ makes contact with the ground. The angle of
the tibial axis with the vertical varies between 70 and 0°. The extremes are
Fig. 1. The arrows indicate lifting ( f ) and replacing ( i ) of the foot at stages 1 and 10,
respectively. The angular changes are given in the upper part; in the lower part the average
periods of muscular activity are represented by the black blocks, individual variations by
the hatched extensions. 1 = M. interosseus; 2 = m. gastrocnemius medialis; 3 = m. gas-
trocnemius lateralis; 4 = m. flexor digitorum superfleialis; 5 = m. hallucis longus; 6 = m.
popliteus; 7 = m. peroneus longus; 8 = m. extensor digitorum longus; 9 = m. tibialis
cranialis;10 = m. gracilis; 11 =m. adductor;12 = m.pectineus;13 = m.semimembranosus
pars cranialis; 14 = m. semimembranosus pars caudalis; 15 = m. semitendinosus; 16 =
m. biceps femoris pars caudalis; 17 = m. biceps femoris pars cranialis; 18 = m. vastus
lateralis (in one dog, activity in the m.vastus medialis was simultaneously with that in the
m. vastus lateralis, as was described by Tokuriki [1973]; so the period of activity of the
m. vastus lateralis is accepted to represent the activity of the whole vastus group); 19 =
m. rectus femoris; 20 = m. tensor fasciae latae; 21 = m. sartorius; 22 = m. gluteus medius.
-ocr page 30-
The action of the hind limb musculature of the dog in walking
STAGE 1
TIME
10
0.1 sec
28
-ocr page 31-
Wentink
Table 1. Body weiglit, gait formula [Hildebrand, 1968], and speed on the trottoir roulant
Dog
Body weight
Gait formula
Speed
kg
m-sec-1
km-h"1
I
23
62/6
1,27
4,6
II
24
63/23
1.19
4.3
III
22
65/22
1.27
4.6
IV
22
63/21
1.25
4.5
V
21
64/20
1.22
4.4
reached in stages 3 and 4 early in the swing phase and in stage 10 at replace-
ment. The angle between the vertical and the axis of the pes varies between
20 and 45 °. The extremes are reached in stages 2 and 3 and 10 and 11, respec-
tively. The gait types of the dogs are expressed according to the formula of
Hildebrand [1968] (table I).
The results of the electromyographic investigations are given in figure 1.
It must be born in mind that registrable electrical activity precedes contraction
by some 20 m-sec-1 and ceases an equal period after this [Grillner, 1972].
The greatest number of muscles is active in stages 9-14 (about the time of
replacement of the foot) and in stages 21-2 (when it is again lifted). Dur-
ing the stance phase the number of muscles in action diminishes, although
the force in ihe horizontal direction - push off - reaches its greatest value at
the end of this phase (stages 20 and 21) [Barclay, 1953]. Muscular activity
is thus largely concentrated in those periods in which there occurs a change
in the sense of the movement of the limb.
The step cycle commences when the foot is lifted. Immediately before
ground contact is lost, the limb is stretched behind the animal and, were it
unopposed, would retain this position and drag behind. In fact, the thigh is
rotated forward as the foot is raised. The stifle is flexed and the hoek follows
suit after a short period of continuing extension. Flexion of the stifle and hoek
shortens the functional length of the limb, bringing the centre of gravity
closer to the centre of rotation at the hip and thus reducing the relative rota-
tional moment of inertia. This economizes the muscular effort required to
advance the foot which, after initially lagging behind, is accelerated to achieve
a forward speed exceeding that of the proximal segments of the limb. The
muscles engaged in these early stages of the swing phase include cranial and
caudal extrinsic muscles of the thigh. The former (tensor and sartorius)
prevail at the hip to overcome the combined inertial and gravitational forces
and the braking effect of the caudal hamstrings. The situation is reversed at
-ocr page 32-
The action of the hind limb musculature of the dog in walking
J.
1                                       6                                           9
J_
10
14
16
0
Fig. 2. The schematic drawings represent successive stages of the step cycle. The active
muscles or groups of muscles are indicated by the smaller lines. In stage 1 the backward
movement of the limb is reversed by the action of the tensor and sartorius. Meanwhile the
stifle is flexed by the action of the caudal hamstrings. The pes is protracted as the tarsus is
flexed by the tibialis cranialis and the peroneus longus. In midswing (stage 6) the limb
continues to be protracted by the sartorius, rectus and extensor digitorum. Just before the
foot is replaced (stage 9), the limb is converted to a strut by the action of the intrisic muscles;
the vastus group, the calf muscles, the interossei, and the extensor digitorum. The forward
swing of the thigh is checked by the cranial hamstring. The strut is maintained by the action
of the intrinsic muscles during the whole stance phase. The caudal hamstrings come into
action at stage 10 to check the forward velocity of crus and pes; they remain active until
the foot passes below the stifle in stage 14. The gluteus and the cranial hamstrings advance
the body over the limb. The retractors cease their activity when the hip has passed over the
foot in stages 16-18. Before the limb is lifted in stage 0, activity ceases in a number of the
muscles which transform the limb into a strut. Contraction of the vasti is replaced by con-
traction of the rectus femoris.
the stifle, where flexion develops against gravity but assisted by inertia. Since
flexion continues after the caudal hamstrings become inactive it must then
be due either to their passive insufficiency (as they are tensed by the continu-
ing flexion of the hip) or to the activity of the caudal belly of the sartorius.
The dorsal crural muscles flex the hoek and impart a forward momentum to
the foot. By the middle of the swing phase the limb has attained its greatest
forward speed and its least functional length. Subsequently it lengthens and
since extension of the hoek precedes activity in the relevant musculature this
-ocr page 33-
Wentink
must be due to gravity and centrifugal force. Inertia maintains the forward
movement but the expected acceleration of the foot as the limb lengthens
does not occur: it must be checked by the passive resistance of the caudal
Vnuscles and periarticular structure since it precedes activity on the relevant
musculature. Immediately prior to the foot re-establishing ground contact,
the cranial hamstrings and probably also the gracilis and adductor will check
the forward velocity of the limb.
The simultaneous activity in the flexors and extensors of the stifle, hoek
and toes appears wasteful but presumably braces the limb against the forth-
coming shock of landing andprepares itfor its supporting role. Several forces
act on the joints on the moment of foot replacement. At the hip, muscular
activity (middle gluteus and all hamstrings) and the horizontal component
of the ground reaction promote extension: inertia and the normal force
promote flexion. The former prevail. The extensor forces acting on the stifle
are inertia, the normal force and the force exerted by the vasti: the flexor
forces are those generated by the caudal hamstrings, gastrocnemii and super-
ficial flexor, and the frictional force. Similarly at the hoek, intertia, the normal
force and the digital extensor act to flex the joint, whilst the calf muscles and
friction tend to extend it. Both joints are flexed.
At the present time the values of most of these forces are unknown;
Barclay [1953] and Hutton et al. [1969] have measured the components of
the ground reaction and have shown that the horizontal component, friction,
is relatively minor in comparison with the normal force and perhaps can be
neglected. This allows certain provisional deductions concerning the relative
importance of the muscular activities. For example, since the tarsal joint is
flexed in spite of the action of the powerful calf muscles, it is clear that the
forces represented by inertia and the normal reaction are dominant.
The stifle first flexes but is soon stabilized. The values of the various forces
acting on the joint have not been determined, but here also the horizontal
component of the ground reaction can perhaps be neglected. The period of
activity of the caudal hamstrings corresponds to that when flexion is observed,
and terminates when the stifle reaches a position directly above the foot
support (stage 14). Applying the results of Barclay [1953], it may be assumed
that between stages 10 and 14 the hind limb has a retarding influence on the
movement of the body and thereafter accelerates it. The potential effects of
contraction of the caudal hamstrings are to retract the limb and to flex the
stifle. Since the vasti are also active and will antagonize any action of the caudal
hamstrings on the stifle it seems probable that their effect is limited to retraction
of the limb. The simultaneous activity in flexors and extensors of the sifle
31
-ocr page 34-
The action of the hind limb musculature of the dog in walking
probably stabilizes this notoriously unstable joint, a role shared by the po-
pliteus, which is now also engaged. Stifle flexion brings the centre of gravity
closer to the centre of rotation at the foot. The curve foliowed by the centre
of gravity is thus flattened, reducing the force required to carry the centre of
gravity over and beyond the foot. The retractor activity of the cranial ham-
strings and the middle gluteal muscle continue until stage 18. No muslces are
active to extend the hip during the last stages of the stance phase and the
final extension of this joint as the body continues forward must be due to
inertia.
The influence of the normal force changes at stage 14; during the remainder
of the stance phase it supplements the flexor activity of the calf muscles in
balancing the vasti and inertia. The quadriceps group (initially the vasti,
later the rectus), both heads of the gastrocnemius, the flexor superficialis and
the hallucis longus approximate the limb to a strut over which the body
moves. The long digital flexors and the interossei press the toes against the
ground, providing a strong grip for support and propulsion. With the onset
of activity in the tensor fasciae latae in stage zero, the cycle recommences.
Discussion
The results of this electromyographic investigation generally confirm
those obtained by Nomura et al. [1966] and Tokuriki [1973] in dogs, and by
Engberg and Lundberg [1969] in cats, but amplify them on a number of
points. The changes of the joint angles are also in general agreement with
those obtained in previous investigations in dogs [Adrian et al., 1966]. Elec-
tromyography reveals which muscles are active when particular movements
are performed; it does not reveal whether the muscle contributes to the move-
ment, opposes it or is merely adjusting its length to the altered positions of its
attachments. The direction of the forces developed by the individual muscles
is determined by their attachments. Although the magnitude of these forces
cannot at present be determined, an indication of their relative values can be
deduced from analysis of the forces operating in each phase of the cycle. By
studying the sequences and durations of activity of the muscles, a concept
was formed of the contribution of each muscle to the movements.
The interpretation offered of the activity of the hamstring group is the
most critical point to emerge. The analysis of the function of these muscles
has long presented difficulties as comparison of a number of anatomical
texts will reveal [Grau, 1943; Bradley and Grahame, 1948; Sisson and
32
-ocr page 35-
Wentink
Fig. 3. AB = Line between origin and insertion of the caudal hamstrings ;Fh = horizontal
component of the force of the caudal hamstrings; S = stifie;P = pads;N = normal force;
W = friction. For explanation, see text.
Grossman, 1955; Nickel et al., 1968]. The results clearly show that the
cranial and caudal parts of this muscle mass do not act synchronously but in
quite different functional contexts. Their prime action as extensors of the
thigh is not in doubt, but their effects upon the stifle require more attention.
Many textbooks describe their actions with reference to the horse and
leave it to be inferred that they are the same in other species; they assert that
the cranial parts are extensors of the stifle whilst the caudal parts (i.e. semi-
tendinosus and caudal biceps femoris) are flexors when the kinetic chain is
open, extensors when it is closed (i.e. when the foot is on the ground). Miller
et al. [1964] and Evans and deLa Hunta [1971], writing specifically of the
dog, ascribe these alternative actions to the caudal parts of the semimem-
branosus and the biceps femoris. Alexander [1974], in a discussion of the
mechanics of jumping in the dog, minimizes the influence of the hamstring
muscles at the stiflle. He ignores any extensor action but ascribes a flexor
function to the caudal parts. The interpretation concerning the function of
the caudal hamstrings given here follows from the analysis shown in figure 3:
AB indicates the line between origin and insertion of the caudal hamstrings
and is the vectorial representation of the muscular force. lts horizontal
component is Fh. If extension of the stifle may be produced by the moment
of Fh about S, there must be present in point P a force in the opposite sense,
with a moment about S of at least equal magnitude to oppose the movement
of the limb segment SP in the sense indicated by the arrow. Since the force W
(friction) acting at point P was shown by Barclay [1953] and Hutton et al.
3
-ocr page 36-
The action of the hind limb musculature of the dog in walking
[1969] to have the same sense as Fh it follows that the caudal hamstrings
cannot extend the stifle in these circumstances. The possibility that in other
circumstances they act as conventionally described is net excluded.
The periods of activity in the extrinsic limb musculature agree with the
predictions of Barcley [1953]. This author found differences between the
horizontal forces actually exerted by the pads and those he expected on
theoretical grounds. He explained these differences by assuming activity in
the cranial extrinsic limb musculature when the limb is retracted and in the
caudal muscles when the limb is protracted, as proved to be the case.
Acknowledgements
The author is indebted to Prof. Dr. K.M. Dyce and Dr. D.M. Badoux for their con-
structive criticism during this study, and to Mr. H. Halsema and to Mr. H. Schiffenstein
for their help in preparing the designs. Thanks are also due to Mr. C.J. Slieker for his
technical assistance, and to Mr. H.H.Otter for the preparation of the films.
References
Adrian, M.J.; Roy, W.E., and Karpovich, P.V.: Normal gait of the dog: an electro-
goniometric study. Am. J. vet. Res. 27: 90-95 (1966).
Alexander, R.McN.: The mechanics of jumping by a dog (Canis familiaris). J. Zool.,
Lond. 173: 549-573 (1974).
Barclay, O.R.: Some aspects of the mechanics of mammalian Iocomotion. J. exp. Biol.
30:116-120 (1953).
Bradley, O.C. and Grahame, T.: Topographical anatomy of the dog; 5th ed. (Oliver &
Boyd, Edinburgh 1948).
Evans, H.E. and deLaHunta, A.: Miller's guide to the dissection of the dog (Saunders,
Philadelphia 1971).
Engberg, J. and Lundberg, A.: An electromyographic analysis of muscular activity in
the hindlimb of the cat during unrestrained Iocomotion. Acta physiol. scand. 75: 614-
630 (1969).
Grau, H.: Das Muskelsystem. Der aktive Bewegungsapparat; in Ellenberger und Baum
Handb. d. vergl. Anat. d. Haustiere; 18. Aufl. (Springer, Berlin 1943).
Grillner, S.: The role of muscle stifness in meeting the changing postural and locomotor
requirements for the force development by the ankle extensors. Acta physiol. scand.
86: 92-108 (1972).
Htldebrand, M.: Symmetrical gaits of dogs in relation to body build. J. Morph. 124:
353-360 (1968).
Hutton, W.C.; Freeman, M.A.R., and Swanson, S.A.V.: The forces exerted by the
pads of the walking dog. J. small Anim. Pract. 10:11-11 (1969).
34
-ocr page 37-
Wentink
Miller, M.E.; Christensen, G.C., and Evans, H.E.: Anatomy of the dog. (Saunders,
Philadelphia 1964).
Nickel, R.; Schummer, A. und Seiferle, E.: Lehrbuch der Anatomie der Haustiere;
3. Aufl. vol. 1 (Parey, Berlin 1968).
Nomura, S.; Sawazaki. H., and Ibaraki, T.: Co-operated muscular action in postural
adjustment and motion in dog, from the view point of electromyographic kinesiology
and joint mechanics. IV. About muscular activity in walk and trot. Jap. J. zoot. Sci.
37: 221-229 (1966).
Sisson, S. and Grossman, J.D.: The anatomy of the domestic animals; 4th ed. (Saunders,
Philadelphia 1955).
Tokuriki, M.: Electromyographic and joint-mechanical studies in quadrupedal locomotion.
I. Walk. Jap. J. vet. Sci. 5: 443-446 (1973).
G.H. Wentink, Institute of Anatomy, Veterinary Faculty, State University Utrecht,
Utrecht (The Netherlands)
\
35
-ocr page 38-
-ocr page 39-
Anatomy
Anat. Embryol. 151, 171-181 (1977)                                                        i i- il         l
and Embryology
© by Springer-Verlag 1977
Biokinetical Analysis of Hind Limb Movements of the Dog
G.H. Wentink
Institute of Veterinary Anatomy, State University, Utrecht, The Netherlands
Summary: This study of movements of the hind limb of the dog was performed
with the aid of cinephotography and electromyography. The weights of the limb
segments and their centers of gravity were determined. From these data the
forces operating at the centers of the limb segments during a cycle of a stride
have been calculated and their influence on the joints have been analysed.
From this study is concluded: 1) muscular activity is present when the effect
of external forces must be overcome and subsides when these external forces act
"positively" in the direction of the progression; 2) gravity and ground-reaction
play an important role in the propulsion of the body, especially when thers is no
activity in the important retractors of the limb at the end of the support phase; 3)
moments about the stifle and tarsal joints are opposite at the end of support
phase and swing phase; 4) activity of the flexor digitorum superficialis (and also
of the gastrocnemius muscles) during the support phase and of the peroneus
longus muscle during the swing phase contribute to the coordination of the
movements and to the stabilization of these joints.
Key words: Biomechanics - Hind limb - Dog - Muscles
Introduction
Animal locomotion involves a close functional interaction between external and
internal forces. External forces comprise gravitation, ground reaction and inertia.
The effect of air resistance may be neglected since the speed at which animals move
is only moderate.
The skeletal muscles provide the most important source of internal force. During
progression the muscles produce a series of coordinated movements of the body and
appendages either to counteract or to strengthen the effect of external forces.
Many studies have been made of mammalian locomotion. The anatomical and
mechanical aspects of locomotion were postulated by Gray (1944). Then
cinephotography (Hildebrand, 1960, 1968; Gambaryan, 1974), electrogoniometry
(Adrian et al., 1966), force platforms (Manter, 1938; Barclay, 1953; Kimura, 1972;
Alexander 1974), and electromyography (Nomura, 1966; Engberg et ai, 1969;
Gambaryan, 1974; Tokuriki, 1974 and 1975; Wentink, 1976) have been employed
individually or in combination to analyze locomotion.
37
-ocr page 40-
G. H. Wentink
However, little information is available on the interplay of internal and external
forces during quadrupedal locomotion. Only Barclay (1946, 1953) points to
differences between recorded and calculated external forces. He predicted activity in
the extrinsic retractors of the limb during protracted limb position and in the extrinsic
protractors during retracted limb position. Both statements were later proved to be
correct (Wentink, 1976).
The purpose of the present study is to investigate the relationship between
external and muscular forces operating at the hind limb of the dog.
Material and M ethods
Six purebred greyhounds and one mongrel greyhound were trained to walk on an encaged treadmill and
filmed from the right lateral side with an exposure rate of 64, 127 or 251 frames per second. The periods
of activity of two muscles at a time were simultaneously amplified with a DISA electromyograph type
14 A 30 and displayed on a Schwarzer recorder (frequency Iimits 75-350 Hz). No attempt was made to
quantify the response: the presence or absence of muscular activity alone was noted (Wentink, 1976).
Periods of muscular activity of the biceps femoris, rectus femoris, sartorius and semitendinosus
muscles were measured in two dogs while walking normally on the ground. The muscular activity
proved to be restricted to the same parts of the normal cycle of a stride as in dogs that walked on the
moving belt (Figs. 5 and 6).
The surface of the moving belt was marked every 10 cm. The sciatic tuber, the coxal tuber, the
major trochanter, the lateral epicondyl of the femur, the proximal and distal ends of the fibula and of the
fifth metatarsal bone were marked with adhesive tape on the skin surface. A switch attached to the right
metatarsal pad indicated the periods at which the foot made contact with the ground.
After termination of the experiments, four dogs (among which was the mongrel greyhound) were
killed by exsanguination, and frozen in toto. The hind limbs were removed and transsected at the pivot
points of stifle and tarsus following the cutting lines indicated in Fig. 1. The limb segments were then
weighed and equilibrated on a sharp metal wedge parallel with and perpendicular to the long axis of the
[                           I
' H
i@ü\
/\J j I Fig. 1. Transsection of the limb in the
f J\ \\ I segments of thigh, leg and foot is
/ \ I /        indicated by the solid horizontal lines;
I I '           the plane of separationofthe limb from
the body is demonstrated in the inset.
Dots indicate the positions of the
adhesive tape on the skin of the animal
38
-ocr page 41-
Biokinetical Analysis of Hind Limb Movements of the Dog
bones. The points of intersection of these two Unes approximated the center of gravity of the limb
segments in a paramedian plane.
In each walking dog, the records of three strides were selected for force calculations. Every second,
flfth or tenth frame (depending on the speed of exposure rate during filming) was analyzed by an
analyzing projector. The transpositions of the marked skeletal points within the cage and the speed of
the moving belt enabled the reconstruction of a normal cycle of a stride in which the positions of the
centers of gravity of the limb segments were plotted. One dog was selected on the basis of its
kinematical performance, the cycle of which is given in Fig. 2.
From this figure the movement of the centers were expressed per unit of time in horizontal (X) and
vertical (Y) directions.
The velocity of the centers of gravity in both directions can be calculated from:
ds
— = v. (m. sec-1).
dt '
The velocity v, was supposed to occur in the middle of the selected time intervals.
The acceleration of the centers of gravity follows from:
dv
— = a. (m. sec-2).
dt '
Multiplication of the mass of the limb segments and the accelerations in the X- and the F-directions
gives the forces Fx and Fy applied at the center of gravity.
Vectorial summation of Fx and Fy gives the resultant Fr of all forces applied at the centers of gravity,
a force which equalizes the sum of gravitational, reactive, and muscular forces and of inertia.
The values of FT have been plotted in the schcmatical representation of the step cycle. The
perpendicular distance from the momentary pivot of the joints (the point of intersection of the lines
connecting the marked skeletal points on one limb segment) to the line of action of Fr is the arm
(d) of the moment, hence the moment is:
M = Fr x d (in Newtonmeters).
For the support phase, this moment was calculated by multiplying the Fr acting at the center of
gravity of the liir.b segment proxirral to the joint under consideration by its proper distance {d) to the
pivot point. For the swing phase the Fr acting at the center of gravity of the limb segment distal to the
joint was multiplied by its distance (d) to determine its moment (Figs. 5,6 and 7).
The Fig. 4-7 represent the calculations of the specimen of Fig. 2. These calculations were similar to
the calculations of the four dogs, in which the centers of gravity were determined.
Results and Interpretation
The principal results of this study are presented in the Figures (2-7). A complete
biokinematical description of the cycle of a stride was presented in a previous paper
(Wentink, 1976), hence only a short description will be presented here.
During placing, the forward foot movement is abruptly stopped resulting in
friction (W) at the point of contact between foot and ground, a force acting opposite
to the forward movement of the body (Fig. 3) (Barclay, 1953; Kimura, 1972).
Following foot placing, the inertia of the thigh and the vertical ground reaction act
together to produce an extensor moment about the stifle joint; friction (W) and
gravity tend to flex this joint. In this period activity is present in the vastus muscles,
which extend the stifle and also in the gastrocnemius and superficial flexor muscles
(the caudal calf muscles) which flex the stifle joint. The combined action of external
and muscular forces work to provide stability of the stifle joint.
Retraction of the limb occurs chiefly by the action of the powerful cranial parts of
the biceps femoris and the semimembranosus muscles (the cranial hamstrings)
assisted by the gluteus, adductor and gracilis muscles; the latter two muscles also
adduct the limb. Shortly thereafter, activity begins in the caudal parts of the biceps
femoris and of the semimembranosus muscles and in the semitendinosus (the caudal
hamstrings). The antagonism between inertia, the ground reaction and the force
39
-ocr page 42-
G. H. Wentink
75______85           95________105            115           125         135_______M5______155          165
Fig. 2. Positions of the limb segments at intervals of 0.08 sec. Solid dots represent the positions of the
skeletal points marked by adhesive tape on the animal. Open circles indicate the averaged positions of
the centres of gravity for the segments (average of four dogs). Arrows indicate the forces (Fr) applied to
the centers of gravity in each stage for this specimen. The frame numbers of the film are given for each
limb position
exerted by the vastus muscles on one side, and friction, gravity, and the force exerted
by the caudal calf muscles on the other (which together stabilize the stifle joint),
enable the caudal hamstrings to assist in the retraction of leg and foot. Thus, during
the support phase the caudal hamstrings retract the limb. Their activity ceases
almost at the moment when the foot passes the vertical through the stifle, which is at
the very moment at which the vertical ground reaction exerts a flexor moment about
the stifle joint. A continued activity of this muscle group beyond this point in the
cycle would otherwise result in a lifting of the foot from the ground by flexion of the
stifle.
The activity in the other part of the hamstrings and of the vastus group stops
nearly at the moment at which the ground reaction exerts a flexor moment about the
stifle joint and an extensor moment about the hip joint, at the same time, activity
begins in the rectus femoris muscle, which antagonizes stifle flexion and hip extension
so that the foot is pressed against the ground.
During the support phase the tarsal joint is held in extension, by the combined
action of the gastrocnemius and by that of the superficial flexor and of the hallucis
longus muscles (Fig. 5). The action of the latter two muscles and the interosseus
muscle presses the toes against the ground and gives the body a mainly upward and
forward impulse.
As soon as the activities in the vastus and gastrocnemius muscles subside, a
marked increase in what were initially small moments about stifle and tarsal joints
occurs.
In the first stages of the swing phase the upward and forward directed impulses
on the limb segments diminish quickly under the effect of gravity and inertia. The
effect of the gravity on leg and foot is opposed by the action of the caudal hamstrings
which lifts both limb segments. Thus, during the swing phase this muscle group acts
as a flexor of the stifle joint.
The actions of the sartorius and the tensor fasciae latae muscles in the swing
phase antagonize the effect of inertia on the mass of thigh and leg. These muscles are
only incidentally assisted by the rectus femoris muscle in the middle of the swing
40
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Biokinetical Analysis of Hind Limb Movements of the Dog
85                                             125
0.05
Fig. 3. Forces exerted by the ground on
the foot during the support phase. Curves
representing the values of these forces are
redrawn after Kimura (1972). W = fric-
tion, N = normal reaction, R = the
resultant of W and N. Extrinsic muscles
which display activity are indicated by the
lines connecting their origin from the pelvis
and their insertion around the stifle; the
caudal group represents the adductor,
gracilis and the hamstring muscles and the
cranial muscle is the rectus femoris.
Positive values of W represent the horizon-
tal ground reaction in the direction of the
progression of the animal, negative values
opposite to the animals movement
0.05-
0.50
Q25-
phase (Fig. 6). The activity of the cranial tibial and the peroneus longus muscles
opposes the effect of inertia on the mass of the foot.
The activities of the peroneus longus and the extensor digitorum longus muscles
in the second half of the swing phase prevent extension of the tarsal joint and flexion
of the digital joints, the latter being caused by gravity and centrifugal forces.
At the end of the swing phase the forward movement of the limb is mastered as
follows: firstly the forward swing of the thigh is counteracted by the action of the
cranial hamstrings, the gracilis and the adductor muscles; secondly the forward
swing of the leg is balanced by the action of the caudal hamstrings. The interval of
time, which the breaking of leg lags behind the breaking of the thigh increases the
lengthof the stride.
The action of the calf muscles controls the forward movement of the foot; the
swing phase ends by placing the foot (replacing the foot) which initiates the frictional
force, and the next cycle commences.
41
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G. H. Wentink
Fig. 4. Forces Fr applied to the centers of
gravity of the limb segments thigh (a), leg (b),
and foot (c) during a complete cycle of a stride
(0-100%) in Newton (N). Forces in the
horizontal direction (X) are given by the solid
lines. Positive values represent forces in the
directions of the progression of the animal.
Negative values represent forces with a
direction contrary to that of the movement of
the animal. Forces in the vertical direction (Y)
are given by the interrupted lines. Positive
values represent forces with an upward direc-
tion. Negative values represent forces with a
downward direction
100%
Discussion
Apparently, there is no activity in the most powerful retractors of the limb when, at
the end of the stance phase, maximum friction occurs in the direction of progression
of the animal (Barclay, 1953; Kimura, 1972). In contrast with this, activity is present
in the rectus femoris muscle at the end of the stance phase, an activity which
antagonizes propulsion.
42
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Biokinetical Analysis of Hind Limb Movements of the Dog
The timing of muscular activity recorded in the experimental but unnatural
conditions did not differ from the results obtained from dogs walking on the ground
(Figs. 5 and 6).
Barclay (1946 and 1953) observed differences between the measured and
the calculated magnitude of the horizontal component of the ground reaction
(friction). The calculated magnitude of friction when the body weight was partially
supported by the limb in its oblique, retracted position was greater than the measured
value. The recorded activity in the rectus femoris muscle in the present study is in
accordance with this observation, since there would be activity in the protractors of
the limb when it is in a retracted position. This activity makes smooth flowing the
otherwise jerky propulsion of the body.
The propulsive effect on the body is ultimately brought about by gravity which,
at the end of the support phase, provokes a ground reaction, the horizontal
component of which acts in the direction of the movement of the body. Therefore, it
is the ground reaction (normal and frictional) which is responsible for the propulsion
of the body during slow progression (Fig. 3). This supposition is in accordance with
Barclay's views (1946, 1953).
The same principles are valid for the progression of the cat in which
approximately the same sequence in the periods of muscular activity of the hind limb
muscles has been recorded (Engberg et al, 1969; Gambaryan, 1974). The
conclusion seems justified, that this principle may be valid for slow quadrupedal
locomotion in general.
During the beginning of the support phase, the animal avails itself of muscle
activity to counteract the effect of the external forces; in fact, the external forces
oppose progression at this period. At the end of this phase the external forces
contribute to progression so that the animal profits from these forces and makes a
minimum use of its muscles.
During the swing phase, the combined effects of gravity and inertia must be
overcome. As soon as the inertia initially operating opposite to the sense of
movement has been overcome (i.e. when the limb moves in the direction of
progression), the activity in the protractors, except the iliopsoas muscle (Tokuriki,
1974) ceases. Then the profitable effect of inertia must be mastered by the activity of
the retractors near the end of the swing phase before the foot is replaced. According
to Hildebrand (1960), in quadrupedal locomotion a large amount of energy is used to
accelerate and to decelerate the limbs during the swing phase.
In the support phase as well as in the swing phase, the animal avails itself of the
external forces, as soon as these contribute to forward movement. The muscles are
called upon during these periods only when the effect of the external forces must be
overcome to make them profitable for the forward impulse of the animal.
Moments about the stille and tarsal joints have an opposite sense during nearly
the entire step cycle. At the end of the support phase there is a strong increment of
the moments about these joints (Fig. 7); the stifle experiences an extensor moment
and, following the cessation of the activity of the gastrocnemius muscle, the tarsal
joint undergoes a flexor moment. The stabilizing influence of this muscle on both
joints is a natural consequence. When the activity of the gastrocnemius muscle
ceases, the superficial flexor coordinates the movements of stifle and tarsus.
At the end of the swing phase the moments about stifle and tarsal joints increase
but in an opposite sense; the stifle experiences a flexor moment and the tarsus an
extensor moment. The peroneus longus muscle antagonizes the opposite moments
about the stifle and tarsal joints in this period of the step cycle.
Thus, the coordination between the movements of stifle and tarsus is largely
43
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G. H. Wentink
Fig. 5. Forces applied to the centers of
gravity of the limb segments during the
support phase are indicated by interrupted
arrows. Their moments about the pivot points
of the stifle and tarsal joints are represented by
M . Muscles which display activity are listed
in the lower part of the figure: numbers 1-8
represent ïecordings when the dogs walked on
the moving belt, numbers 9 and 10 when the
dogs walked on the ground. 1, Cranial
hamstrings; 2, Caudal hamstrings; 3, M.
adductor and M. gracilis; 4, M. gluteus
medius and M. gluteus superficialis; 5, M.
vastus lateralis; 6, M. rectus femoris; 7, M.
gastrocnemius medialis and lateralis; 5, M.
flexor superficialis, M. hallucis longus, and M.
interosseus; 9, Cranial part of M. biceps
femoris; 10, M. rectus femoris
m
muscular activtty                    occasional musc. act.
O,
brought about by the superficial flexor and the peroneus longus muscles. (In the
horse there is a strong tendinous component in the analogous muscles, a subject
which will be considered in a future report.)
On a strictly anatomical basis the muscles of the hind limb can be divided as
foUows: 1) origins and insertions, distinguishing between extrinsic muscles which
originate from the skeleton of the trunk, and intrinsic muscles which take their origin
from the limb bones (Gray, 1944). 2) The internal organization of the muscles; either
parallel-fibered or pennate.
The extrinsic muscles are a functional entity; they form a loop which begins at
the ilium, cranially to the hip joint, and passes to the distal part of the femur and the
44
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Biokinetical Analysis of Hind Limb Movements of the Dog
135           155
Fig. 6. Forces operant during the swing phase in
the centers of gravity of the limb segments and
their moments (Mb) about the pivot points of stift1 e
and tarsal joints. Muscles which display activity
are given in the lower part of the figure. Numbers
1-6 represent recordings when the dogs walked
on the moving belt, numbers 7 and 8 when the
dogs walked on the ground. 1, caudal hamstrings;
2, cranial hamstrings; 3, M. adductor and M.
gracilis; 4, M. sartorius and M. tensor fasciae
latae; 5, M. tibialis cranialis, M. extensor
digitorum longus and M. peroneus longus; 6, M.
rectus femoris; 7, M. sartorius; 8, M. semi-
tendinosus
proximal end of the tibia. The caudal part of the loop extends from these bones
to the sciatic tuber of the pelvis caudal to the hip joint. An exception is made for the
rectus femoris muscle, which is included in the group of intrinsic muscles (see below).
The limb is in fact suspended in this loop, the cranial part of which (tensor
fasciae latae, sartorius, iliopsoas muscles) displays its activity mainly in the
beginning of the swing phase and counteracts the effect of inertia. The caudal part of
the loop (the semitendinosus and cranial and caudal parts of the biceps femoris, and
the semimembranosus muscles in which the gluteal muscles may also be included)
exerts its activity at the end of the swing phase in order to stop the forward
movement of the limb, first that of the thigh and then that of the leg. The latter group
remains active in the first half of the support phase and counteracts the initial
negative effect of the friction by retraction of the limb. A comparable interpretation
has been given of the action of the extrinsic muscles in man (Groh, 1974).
One group of intrinsic muscles displays activity in the beginning of the swing
phase: the intrinsic muscles on the dorsal side of the tibia (cranial tibial, extensor
digitorum longus, peroneus longus muscles). Their action is also to counteract the
effect of inertia in the beginning of the swing phase. The muscles of both groups are
parallel-fibered; their prime action is to overcome the negative effect of the external
forces and to bring about the movements of the limb.
Of the remaining intrinsic muscles some display activity during the entire support
phase, others during only definite periods of the support phase. The activity of the
rectus femoris muscle occurs mainly during this phase. Although this muscle is
extrinsic in nature, it is included in this group. The function of this group of intrinsic
45
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G. H. Wentink
Fig. 7. Moments (of the forces applied to the
centers of gravity cf the limb segments) about
the stifle joint (solid line) and about the tarsal
joint (interrupted line) in Newtonmeters (Nm).
Activities of gastrocnemius (1), superficial
flexor (2) and peroneus longus (3) muscles are
given in the lower part of the figure
muscles is to transform the limb into a "strut" over which the body moves forward.
These muscles are pennate.
The parallel-fibered muscles move the intrinsic joints of the limb while the
pennate muscles provide the stability of the limb during the support phase.
Acknowledgement: The author is very much indebted to Dr. D.M. Badoux for his constructive criticism
during this study. Gratitude is also expressed to Mr. H. Schiffestein for the preparation of the schematic
illustrations and to Mr. M. Klein, of Stichting Film en Wetenschap, Utrecht, for making the films used
in this study.
References
Adrian, M.J., Roy, W.E., Karpovich, P.V.: Normal gait of the dog: an electrogoniometric study. Am. J.
Vet. Res. 27,90-95(1966)
Alexander, R.McN.: The mechanics of jumping by a dog (Canis familiaris). J. Zool. Lond. 173, 549-
573 (1974)
Barclay, O.R.: The mechanics of amphibian locomotion. J. Exp. Biol. 23, 177-203 (1946)
Barclay, O.R.: Some aspects of the mechanics of mammalian locomotion. J. Exp. Biol. 30, 116-120
(1953)
Engberg, J., Lundberg, A.: An electromyographic analysis of muscular activity in the hind limb of the
cat during unrestrained locomotion. Acta physiol. Scan. 75, 614-630 (1969)
46
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Biokinetical Analysis of Hind Limb Movements of the Dog
Gambaryan, P.P.: How animals run. New York-Toronto: John Wiley & Sons (1974)
Gray, J.: Studies in the mechanics of the tetrapod skeleton. J. Exp. Biol. 20, 88-116 (1944)
Groh, H.: Die Krafte bei menschlicher Korperbewegung. In: Biopolymere und Biomechanik von
Bindegewebesystemen (F. Hartmann, ed.) Berlin-Heidelberg-New York: Springer Verlag, 1974
.Hildebrand, M.: How animals run. Sci. Am. 5, 148-157 (1960)
Hildebrand, M.: Symmetrical gaits of dogs in relation to body build. J. Morphol. 124, 353-360 (1968)
Kimura, T., Endo, B.: Comparison of force of foot between quadrupedal walking of dog and bipedal
walking of man. J. Fac. Sci. Uni. Tokyo 5, 119-130 (1972)
Manter, J.T.: The dynamics of quadrupedal walking. J. Exp. Biol. 15, 522-540 (1938)
Tokuriki, M.: Electromyographic and joint-mechanical studies in quadrupedal locomotion. I. Walk.
Jap. J. Vet. Sci. 5, 433-446 (1973)
Received December 9,1976
4
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Anatomy
and Embryology
Anat. Embryol. 152, 261-272 (1978)
©by Springer-Verlag 1978
Biokinetical Analysis of the Movements of the Pelvic Limb of the
Horse and the Role of the Muscles in the Walk and the Trot
G. H. Wentink
Institute of Veterinary Anatomy, State University, Bekkerstraat 141, Utrecht, The Netherlands
Summary. The movements of the right hind limb of horses with normal
locomotion were studied using cinephotography and electromyography. A model
of the cycle of a stride in the walk and the trot was constructed and the kinetic
parameters of the segments of the limb were calculated. A good correlation was
obtained between the kinetics and the periods of the cycle of a stride during
which individual muscles display activity. The results of this study demonstrate
that:
a) The number of muscles displaying activity is greatest at placing and lifting,
i.e., when a change occurs in the direction of the movement of the limb;
b)  At the walk, the greatest forces operant at the centres of gravity of the
limb segments in the direction of the progression are present in the beginning and
the end of the support phasc. The first top in the acceleration curve is produced
by activity in the retractors of the limb (hamstrings, gluteus medius muscles). At
the end of the support phase, when activity in the retractors of the limb no longer
exists, the dynamic effect of the moment of the weight about the point of support
of the stabilized inclined limb, as well as the elastic resilience of the muscular
tissue are responsible for the push-off. At the trot, the greatest forces in the
direction of progression are exerted in the middle of the support phase and are
largely due to muscular action;
c) In the second part of the support phase in the walk, the stifle flexes and the
hoek extends, which results in stretching the tendinous peroneus tertius and
subsequently in flexion of the hoek as soon as the hoof starts rolling over;
d)  The gastrocnemius and cranial tibial muscles in the reciprocal tendinous
apparatus centre the line of action of the resultant load on the tibia during the
locomotion and reduce the strain due to bending;
e) At the end of the support phase, the action of the rectus femoris muscle is
replaced by that of the vastus lateralis, which prevents hooking of the patella on
the medial ridge of the femoral trochlea by rotating it laterally around a
longitudinal axis.
Key words: Biomechanics - Hind limb - Horse - Locomotion - Muscles
0340-2061/78/0152/0261/S02.40
49
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G. H. Wentink
I. Introduction
Many investigators have studied the locomotion of horses, using cinephotography
(Hildebrand, 1960, 1965; Fredricson and Drevemo, 1972; Rooney, 1969, 1975),
electrogoniometry (Taylor et al., 1966)), thermography (Dalin et al., 1973), force
plates (Bjórk, 1958; Pratt and O'Connor, 1976), or a theoretical approach based
upon anatomical and physical data (Badoux, 1973; Bradley and Grahame, 1946;
Grau, 1943; Gray, 1944, 1956; Seiferle, 1968; Sisson, 1975).
The results of these studies are either restricted to the statical situation or to tne
kinematics of the limbs. Whenever muscular functions are described, any
experimental verification concerning the actions of the muscles during natural
progression is lacking, hence the conclusions about the function of the muscles are
based on 'common sense' deductions from the loei of origin and insertion of the
muscles or on direct visual observation of moving horses.
In this context, the role of the crural reciprocal apparatus, consisting of the
superficial flexor and peroneus tertius muscles, has been explained within the
function of the stay apparatus (Badoux, 1970; Bradley and Grahame, 1946; Grau,
1943; Seiferle, 1968; Sisson, 1975).
In veterinary anatomical text books, only scanty Information is found about the
role of these muscles during progression.
The purposes of the present report are: (a) to give information on the periods of
the step cycle during which some muscles of the hind limb of the horse display
activity; (b) to describe the interplay of muscular and external forces (inertia,
gravity, ground reaction); and (c) to give an explanation of the role of the muscles
during progression. In this study cinephotography and electromyography were used.
Walk is defined as the regular, slow and stable mode of progression, during
which two or three feet are alternately in contact with the ground; each foot is lifted
only after replacement of its contra-lateral fellow. The support phase is about 60% of
a complete step cycle.
Trot is defined as a rather speedy gait, during whioh the limbs are moved and
placed in a regular diagonal pattern; during the suspension phase no feet are in
contact with the ground. The support phase is about 40% of a complete step cycle.
II. Materials and Methods
Eight ponies and horses with normal locomotion were used for the experiments. The characteristics of
the individual animals are given in Table 1.
The animals were filmed (exposure rate: 110 to 125 frames per second) from the right lateral side in
the walk and the trot, while their reins were kept loose. The skin over the sciatic tuber, coxal tuber,
major trochanter and lateral epicondyle of the femur, the lateral condyle and lateral malleolus of the
tibia, and the lateral proximal and distal ends of the metatarsus was marked with pieces of adhesive tape
measuring one square centimeter. The animals were also filmed while standing square. The outlines of
the femur, tibia and metatarsus were reconstructed and then traced onto every eighth frame of the film.
Since the skin over the coxal and sciatic tuber is only slightly movable, these skeletal landmarks were
redrawn directly from the film frames. The lines connecting the landmarks on the pelvis, femur, tibia
and metatarus, respectively give information on the geometrical changes occurring at the joints during
progression. The angles at the intersection of these lines were measured over the flexor aspect of the
joints, and by this procedure normal cycles of a stride in the walk and the trot were reconstructed (Fig.
2).
Five animals were trained to walk and trot on a moving belt for electromyographic studies. Two
platinum wire electrodes from which the insulation of the terminal 1-2 mm had been removed were
inserted into the muscle bellies of the right hind limb (Wentink, 1976).
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Biokinetical Analysis of the Movements of the Pelvic Limb
Table 1. Characteristics of the individual horses
Horse
Breed
Sex
Age
Body weight
(kg)
Height at
the withers
(m)
I
Gelder
male
9 months
274
1.46
II
Gelder
male
8 months
263
1.41
III
Welsh
male castrated
3 years
246
1.30
IV
Welsh
male castrated
3 years
332
1.45
V
Fjord
female
7 years
520
1.54
VI
Welsh
male castrated
6 years
362
1.44
VII
Fjord
female
6 years
490
1.51
VIII
Welsh
male castrated
5 years
288
1.30
The periods of activity of three muscles (always including the tensor fasciae latae) were
simultaneously assessed from the loudspeaker and monitor of a DISA Electromyograph type 14 A 30
(frequency limits: 75-1000 Hz) and registered on a magnetic tape recorder (Bell & Howell, type VR
3200). No attempt was made to quantify the response: only the presence or absence of muscular
activity was noted. During the experiments a switch, attached under the right hind hoof, closed a circuit
when touching the ground; this contact was registered on the tape simultaneously with the EMG
signals. During one session, when the horses were filmed from an oblique frontal position, closure of the
circuit was arranged to illuminate a lamp in the picture field. The simultaneous registration of the circuit
signals on the tape recorder and the film establishes a good correlation.
After the experiments, four horses were killed by exsanguination and fixed with a 10% formalin
solution. Their hind limbs were removed and divided into thigh, shank and metatarsus (Fig. 1).
Fig. 1. Transsection of the limb in the
segments thigh, shank, metatarsus and
digit is indicated by solid horizontal
lines. The place of separation of the
limb from the body is given by the solid
line in the inset. The black dots indicate
the positions of the markings on the
animal
51
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G. H. Wentink
The weights of the segments were determined. They were then photographed, while suspended by
a rope attached to the segments in a paramedian plane at two different points in successive
photographs. The point of intersection of the vertical lines in the two positions was taken as the centre
of gravity of the segments, and this was plotted into the reconstructed cycle of a stride. From these
figures, the displacements of the centres of gravity were derived per unit of time in horizontal (X) and
vertical (Y) directions. Velocity (v), acceleration (a) and force (F) in both directions applied to the
centres of gravity follow from:
ds
V=d7                                                                                                   (1)
a = ^                                                                                                                                        (2)
dt
F = m.a                                                                                                                                      (3)
The magnitude of the velocity, acceleration and force were calculated for the middle of the time
intervals initially chosen.
III. Results
The results are given in Tables 2 and 3 and in Figures 2, 3, 4, 5 and 6. The gait is
characterized by the gait formula of Hildebrand (1965), the first number giving the
percentage of the step cycle during which the hind limb is in contact with the ground,
and the second number the percentage of the step cycle by which the footfall of the
right fore limb lags behind that of the right hind limb.
At the walk, the (caudal part of) the greater trochanter—and the
acetabulum—follow an undulating path. The difference between the highest and
lowest points of this course is about 5% of the height at the withers. The
perpendicular distance from the greater trochanter to the ground is greatest in the
middle of the support and swing phases, and is least at lifting and replacing the limb
when both hind limbs are in contact with the ground. The perpendicular distance is
somewhat greater in the support phase than in the swing phase, which means that the
pelvis drops around a longitudinal axis to the unsupported side.
Table 2. The extreme positions of the individual limb segments
Maximal
Percent of
Maximal
Percent of
protraction
the cycle
retraction
the cycle
Walk
Thigh
+ 38°
95%
+ 6°
55%
Crus
+4°
100%
-55°
60%
Metatarsus
+40°
90%
-21°
55%
Trot
Thigh
+35°
85%
+ 8°
40%
Crus
0°
100%
-55°
60%
Metatarsus
+45°
80%
-21°
40%
+: cranial in front of a perpendicular line.
—: caudal of a perpendicular line.
The angle is formed between the perpendicular line from the proximal point of the limb
segment indicated and the line connecting the proximal and distal point of the segments
of the limb.
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Biokinetical Analysis of the Movements of the Pelvic Limb
Table 3. Characteristics of the gait of the individual horses
Horse             Velocity               Step formula Time swing          Time support
(km/hr)                                          (seconds)             (seconds)
Walk
I
5.8
62/26
0.39
0.63
II
5.7
62/27
0.38
0.62
III
5.8
63/23
0.34
0.58
IV
6.2
64/24
0.36
0.63
V
5.5
66/26
0.38
0.75
VI
6.5
61/31
0.33
0.52
VII
6.5
63/24
0.36
0.61
VIII
5.1
63/23
0.32
0.54
Trot
I
10.8
39/51
0.41
0.26
II
10.5
42/52
0.37
0.27
III
12.3
41/52
0.31
0.21
IV
16.5
40/53
0.32
0.22
V
16.6
48/51
0.33
0.30
VI
14.7
45/50
0.28
0.23
VII
16.1
40/49
0.32
0.22
VIII
12.4
40/49
0.31
0.21
The swing of the hind limb measured by the angle formed between the lines
connecting the caudal part of the greater trochanter and the distal part of the
metatarsus in the retracted and protracted position is 43°: the retraction caudal to
the perpendicular is 19°, the protraction cranial to that line is 24°. For further details
of the kinematics of the cycle of a stride see Tables 2 and 3, and Figures 2, 3 and 5.
There is flexion of the stifle in the second part of the support phase and extension
of the hoek in the same period, hence a considerable stretch must develop in the
peroneus tertius. This results in flexion of the hoek at the end of the support phase,
when the hoof starts turning over. During the swing phase and the first part of the
support phase the changes at stifle and hoek have the same sense.
At the trot, the highest points on the undulating course of the acetabulum are
reached in the beginning and end of the swing phase. The lowest points are reached
in the middle of the support and swing phase: in the middle of the swing phase the
perpendicular distance between the greater trochanter and the ground is somewhat
greater than in the support phase, which means that the pelvis is lifted around a
longitudinal axis to the unsupported side. The difference between the highest and
lowest points of the path of the acetabulum is about 4.5% of the height at the withers.
The hindlimb makes a swing from maximal retraction to maximal protraction of
37°: the retraction is 16° and the protraction is 21°. For further details see Tables 2
and 3, and Figures 2, 3 and 5. The changes in the stifle and hoek joints in the second
part of the support phase do not diverge as much in the trot as in the walk: the angle
at the stifle is almost constant after the initial flexion in the first part of the support
phase.
At placing in the walk and the trot, the hoof of the hind limb still has some
forward velocity; the velocity of the front hoof, however, is zero at placement, as
already described by Rooney (1969).
The periods in which the muscles display activity are grossly the same in the
walk and the trot (Fig. 4). The parts of the biceps femoris, semitendinosus and
53
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G. H. Wentink
Fig. 2A and B. Position of the limb segments in the walk (A) and the trot (B) at intervals of 0.08 s. The
dots give the positions of the marked skeletal points, the squares the positions of the centres of gravity.
The arrowheads indicate the sense of the forces applied to the centres of gravity in each stage
semimembranosus originating from the sacral vertebrae and sacro-sciatic ligaments
displayed activity in incidental strides of a single horse. In the trot, however, these
muscular heads are active in every stride. Activity is present in the greatest number
of muscles at placing and lifting of the leg; the number of muscles displaying activity
diminishes during the support phase and also during the swing phase. Thus,
muscular activity is largely concentrated in those periods, in which there is a change
in the sense of the movement of the limb.
When maximal friction in the direction of the movement of the animal is present
at the end of the support phase (Pratt and O'Connor, 1976) there is activity in a
protractor of the limb (tensor fasciae latae muscle) which antagonizes propulsion—
hence other factors must contribute to the push-off at the walk.
54
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Biokinetical Analysis of the Movements of the Pelvic Limb
Fig. 3A and B. The angular changes of the hip (a), stifle (b) and hoek (c) in the walk (A) and the trot
(B). The support phase is indicated by the solid horizontal line at the bottom of the figure
|support [ swing
0.1 sec«M           B
L_
su pport
|swing
0.1 sec
Fig. 4A and B. The average periods of activity of the muscles during the walk (A) is given by the black
blocks, the extremes of incidental periodical activity are represented by the white extensions. For the
trot (B) incidental periodical muscular activity is only given for the cranial tibial and gastrocnemius
muscles. Further, all muscular activity has been listed by black blocks. 1. M. tensor fasciae latae; 2. M.
vastus lateralis; 3. M. rectus femoris; 4. M. gluteus medius; 5. M. gluteus superficialis; 6. sacral heads of
M. biceps femoris, M. semitendinosus and M. semimembranosus; 7. cranial part of M. biceps femoris;
8. M. caudal part of M. biceps femoris; 9. M. semitendinosus; 10. M. gastrocnemius; 11. M. hallucis
longus; 12. M. tibialis cranialis; 13. M. extensor pedis longus
55
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G. H. Wentink
Fig. 5A and B. The forces applied to the centres of gravity of the thigh (a), shank (b), and metatarsus
(c) in the walk (A) and the trot (B). Forces in the X-direction are given by solid Unes, forces in the Y-
direction by interrupted lines. Positive values represent forces with a forward (X) or upward (Y)
direction, negative values indicate forces in a backward (X) or downward (Y) direction
At placing, the resultant of the external forces at the hoof (friction, inertia,
normal reaction) and at the hip (inertia, body weight) flex stifle and hoek (Fig. 6).
This is counteracted by the action of the rectus femoris, gastrocnemius and deep
digital flexor muscles. These muscles transform the limb into a strut over which the
body moves as over a spoke. The action of the deep digital flexor antagonizes
overextension of the digit.
In the first part of the support phase the friction is opposite to the movement of
the body. The couple formed by the forces in the vertical direction operating at hoof
and hip is of a greater magnitude than that formed by the horizontal forces, so that
the former tends to turn the right limb in an anticlockwise direction (Fig. 6).
Friction and the couple in the vertical direction counteract progression and they
are antagonized by the forces exerted by the retractors of the limb, i.e., the three
parts of the biceps femoris, the semitendinosus, the medial gluteal muscles, and
probably also the gracilis, adductor and semimembranosus muscles, which retract
the stabilized limb. Extension of the stifle by the action of the caudal and middle
parts of the biceps femoris and the semitendinosus muscles is not possible; the
horizontal component of the force exerted by these muscles has a flexor moment
about the stifle joint (cf. the situation in the dog, Wentink, 1976; Gray, 1956).
Extension of the stifle by these muscles could be established by a force distal to the
stifle exerting an extensor moment about this joint. However, in the first part of the
support phase, the friction and the horizontal component of the muscular force are
colinear; the stifle is kept extended throughout the support phase by subsequent
56
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Biokinetical Analysis of the Movements of the Pelvic Limb
Fig. 6A and B. Position of the limb segments at placing (A) and lifting (B). G = weight; I = inertia; R =
resultant; W = friction; N = normal reaction. In the force G the effect of the inertia due to the
undulating course of the pelvis is included
action of the quadriceps components, the rectus femoris and then the lateral vastus.
The retractors of the limb cease their activity when the acetabulum has moved over
the supporting hoof. The push-off in the final part of the support phase cannot
therefore be provoked by the action of the retractors of the limb.
In the last stages of the support phase, the hoek extends against muscular action,
since its extension is antagonized by the tendinosus peroneus tertius and the cranial
tibial muscle, which now displays activity. The force of inertia, which has a sense
opposite to the force operating at the centre of gravity (Fig. 5), the action of the deep
digital flexor and the normal reaction extend this joint. Though the magnitude of
these forces cannot be calculated exactly, extension of the hoek stresses the relative
importance of the effect cf inertia and the normal reaction. The digital flexors
contribute to the push-off by flexion of the digit, pressing the hoof against the ground.
The swing is initiated by the action of the tensor fasciae latae muscle at the end of
the support phase, probably supported by the actions of the iliopsoas and sartorius
muscles. As soon as the limb moves in a forward direction, the activity in the former
muscles subsides. The limb is shortened by flexion of the stifle, which is brought
about the action of the caudal part of the biceps, frequently assisted by the middle
part of this muscle and by the action of the semitendinosus. In the swing phase the
caudal and middle parts of the biceps femoris and the semitendinosus muscles act as
flexors of the stifle.
The hoek is flexed by the cranial tibial muscle and by the elastic energy of the
peroneus tertius tendon, stored during the stretching of this elastic band in the second
part of the support phase by opposite movements of stifle and hoek. The digital
extensor opposes the effect of inertia of the digit. Shortening of the limb brings the
57
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G. H. Wentink
centre of gravity of the limb closer to the pivot point at the hip and thus reduces the
moment of inertia about the hip joint.
In the second part of the swing phase activity begins in all retractors of the limb,
bracing the effect of inertia which tends to continue the forward movement of the
limb. Activity starts also in those muscles which transform the limb into a strut and
prepare it for placing.
IV. Discussion
The changes in the joint angles found in this study are in general agreement with
those described by Taylor et al. (1966), Gambaryan (1974) for the tarsal joint and by
Rooney (1969, 1975) for tarsal and stifle joints (namely flexion of the stifle and
extension of the hoek in the second part of the support phase). The difference in the
numerical values are probably due to the different breeds investigated.
Electromyography only reveals which muscles are actively involved in the
specific movements. The line of action of the force developed by an individual muscle
follows from its loei of origin and insertion. Although the exact magnitudes of the
forces are unknown, their action can be appreciated by analysing their overall effect
during a stride, and the specific contribution of various groups of muscles to the
movement can be deduced.
In the walk, the highest point of the undulating course of the acetabulum is
reached in the middle of the support phase (Fig. 2). It is brought into that position by
the action of the retractors of the limb, pushing the body forward over the stabilized
limb and opposing the couple of vertical forces, operating at hip and hoof, and the
friction, both of which counteract progression (Fig. 6).
The activity of the retractors ceases shortly after the middle of the support phase.
At that moment, the couple of vertical forces favours progression. The second top of
the acceleration at the end of the support phase is evoked without activity in the
retractors of the limb. The push-off at the walk must be largely attributed to the
dynamical effect of the weight, supported by the inclined limb, which provokes a
friction in the direction of the movement (Fig. 6). Further, the remaining elastic
tension in the muscles is involved in the push-off. Thus, at the walk, the muscles
antagonize the external forces which oppose the forward movement of the animal
and they cease their activity when the external forces contribute effectively to the
progression. During the first part of the support phase at the trot the dynamical effect
of the body weight is flattened out; in the middle of the support phase the maximal
forces in X and Y directions (Fig. 5) are exerted by the action of the gluteus medius
muscle and by the hamstrings, whose sacral heads are now also actively involved.
The acetabulum reaches its highest point immediately after the support phase. The
push-off in the trot is largely achieved by the action of muscles. The trot requires
more muscular energy than the walk, because of the faster movements of the limbs in
the swing phases, but the forces operating at the centres of gravity of the limb
segments are smaller than in the walk (Fig. 5).
Badoux (1970), dealing with the function of the gastrocnemius muscle in the
reciprocal tendinous apparatus, demonstrated a reduction of the compressive and
tensile strain in the tibia in a statical situation.
At placing, in the walk and the trot, the effect of inertia tends to continue the
movement of the body. This causes bending and a corresponding tensile strain over
the plantar and a compressive strain over the dorsal aspect of the tibia (Lanyon and
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Biokinetical Analysis of the Movements of the Pelvic Limb
Smith, 1970). The tensile strain may be reduced by contraction of the gastrocnemius
muscle, which is actually active in this period of the cycle of the stride, and which
produces a counteracting moment of the tibia. These observations support Badoux's
calculations.
At the end of the support phase there is no activity in this muscle. In the walk, the
greatest force in the direction of the movement of the animal is achieved at the end of
the support phase, and thus the effect of inertia which counteracts the forward force
is maximal. Therefore, a tensile strain over the dorsal and a compressive strain over
the plantar aspect of the tibia may be expected (Badoux, 1973). The tensile strain can
be reduced by the contraction of the cranial tibial muscle, which also prevents over-
extension of the hoek. Activity in the cranial tibial muscle in the end of the support
phase supports the 'cunian' tendon operation in spavin (Adams, 1966).
In the trot, the maximal force in the horizontal direction is exerted in the middle
of the support phase. At the end of this phase, this force and inertia are both so small
that no activity is required in the cranial tibial muscle. In our opinion the muscles in
the reciprocal tendinous apparatus centre the line of action of the resultant load on
the tibia during locomotion and consequently reduce the stress due to bending.
A large amount of energy required for quadrupedal locomotion is spent when
accelerating and decelerating the limbs in the swing phase (Hildebrand, 1960). In the
swing, the centre of gravity of the limb should be brought as closely as possible to the
pivot point at the hip which reduces the accelerating moments. Replacing muscular
tissue by tendons, which display a potential to flex and to extend the hoek, brings the
centre of gravity closer to the hip and therefore reduces the energy necessary during
the swing phase.
The unlocking of the patellar mechanism of the stifle joint is ascribed to the
biceps femoris muscle or to the lateral vastus muscle (Grau, 1943; Seiferle, 1968;
Sisson, 1975). In the support phase activity is first present in the rectus femoris and
subsequently in the lateral vastus. Continuing activity in the rectus throughout the
support phase would interfere with the tilting of the patella over the femoral trochlea.
The lateral vastus extends the stifle and turns the patella around a longitudinal axis
running from the middle of its base towards its apex, and pulls it in a lateral direction.
This muscle prevents hooking of the patella on the medial ridge of the femoral
trochlea, assisted by the middle part of the biceps femoris muscle.
Acknowledgement. Thanks are due to Dr. D.M. Badoux for his constructive criticism, to Mr. CJ.
Slieker for his technical assistance, and to Mr. M. Klein and Mr. Chr. van Nieuwenhuizen for the
preparation of the films.
References
Adams, O.R.: Lameness in horses. Philadelphia: Lea & Febiger (2nd ed.) 1966
Badoux, D.M.: The statical function of some crural muscles in the horse. Act. Anat. 75, 396-407
(1970)
Badoux, D.M.: Biomechanics of the third metatarsal bone in the horse. Proc. Kon. Ned. Akad. v.
Wetensch., C78, 257-269 (1973)
Björk, G.: Studies on the draught force of horses. Acta Agric. Scand., suppl. 4 (1958)
Bradley, O.C., Grahame, T.: The topographical anatomy of the limbs of the horse, 2nd ed. Edinburgh:
Green & Son (1946)
Dalin, G., Drevemo, S., Fredricson, J., Jonsson, K.: Ergonomie aspects of locomotor asymmetry in
Standard bred horses trotting through turns. Acta Vet. Scand. suppl. 44 (1973)
59
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G. H. Wentink
Fredricson, I., Drevemo, S.: A photogrammetric method of two-dimensional fast moving horses. Acta
Vet. Scand. suppl. 37(1972)
Gambaryan, P.P.: How mammals run. New York, Toronto: John Wiley & Sons 1974
Grau, H.: Das Muskelsystem. Der aktive Bewegungsapparat. In: Elleberger und Baum, Handbuch der
vergleichende Anatomie der Haustiere (18e ed.) Berlin-Heidelberg-New York: Springer Verlag 1943
(reprint 1974)
Gray, J.: Studies in the mechanics of the tetrapod skeleton. J. Exp. Biol. 20, 88-116 (1944)
Gray, J.: Muscular activity during locomotion. Brit. Med. Buil. 12, 203-209 (1956)
Hildebrand, M: How animals run. Sci. Amer. 5, 148-157 (1960)
Hildebrand, M.: Symmetrical gaits of horses. Science 150, 701-708 (1965)
Lanyon, L.E., Smith, R.N.: Bone strain in the tibia during normal quadrupedal locomotion. Acta
Orthop. Scand. 41, 238-248 (1970)
Pratt, G.W., O'Connor, J.T.: Force plate studies of equine biomechanics. Am. J. Vet. Res. 37, 1251—
1255 (1976)
Rooney, J.R.: Biomechanics of lameness in horses. Baltimore: Williams and Wilkihs 1969
Rooney, J.R.: The lame horse. Cranbury, New Jersey: Barnes and Co. 1975
Seiferle, E.: Aktiver Bewegungsapparat, Muskelsystem. In: Lehrbuch der Anatomie der Haustiere,
Band I (ed. R. Nickel, A. Schummer, E. Seiferle) Berlin/Hamburg: Paul Parey, dritte Auflage, 1968
Sisson, S.: Myologie (Equine). In: Sisson and Grossman's The anatomy of the domestic animals (ed. R.
Getty) 5th ed. Philadelphia-London-Toronto: Saunders 1975
Taylor, B.M., Tipton, C.M., Adrian, M., Karpovich, P.V.: Action of certain joints in the legs of the
horse recorded electrogoniometrically. Am. J. Vet. Res. 116, 85-89 (1966)
Wentink, G.H.: The action of the hind limb musculature of the dog in walking. Acta Anat. 96, 70-80
(1976)
Received September 28,1977
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DYNAMICS OF THE HIND LIMB AT WALK IN HORSE AND DOG.
G.H. WENTINK
Institute of Veterinary Anatomy, State University Utrecht
SUMMARY
The dynamics of the hind limbs of the horse and the dog
at the walk are compared. The kinematics were studied by
electromyography in animals walking on a moving belt, and
by cinephotography in horses walking on the ground and in
dogs walking on a moving belt and on the ground.
This study reveals that: 1) the retraction of the hoof
(foot) relative to the hip at the end of the support phase
is less in the horse than in the dog; 2) the change in
the sense of the movements of the hind limb segments at
the end of the support phase and in the begin of thé swing
phase occurs earlier in the horse (55-60 % of the cycle of
a stride) than in the dog (70 %); 3) there is in both
species no activity in the retractor muscles of the hind limb
at the end of the support phase, so that the push-off is
effectuated by the dynamic effect of the load (gravity),
and the elastic resilience in the retractor muscles; 4)
in the horse, the cannon passes beyond the vertical and makes
it necessary to bring the cranial tibial muscle into action
to prevent overextension of the hoek joint; in the dpg,
the metatarsus remains in an approximately vertical
position and the superficial digital flexor muscle remains
active throughout the support phase; 5) at placing, the
moment of F (fig. 1) about the foot provokes a tensile
strain on the plantar aspect of the tibia and a compressive
strain on its dorsal aspect: the action of the gastroc-
nemius muscle centres the line .of action of the load on
the tibia in this phase; 6) at the end of the support
phase the relatively greater moment of F about the hoof
in the horse makes it necessary to bring the cranial
tibial muscle into action to centre the line of action
of the load on the tibia; 7) the tendinous interosseus
and superficial digital flexor muscle of the horse store
elastic energy at impact and use this energy to stretch,
the peroneus tertius tendon, which energy is ultimately
used to flex the hoek at lifting; the superficial digital
flexor and the peroneus tertius tendons coordinate the
movements of stifle and hoek during the swing phases;
all the components mentioned save energy: the horse is
an animal build for great stamina; 8) in the dog the
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analoga of the aforementioned tendons are muscular and, in
consequence, the dog is able to dig the digits and claws
into the ground for a strong grip and great friction: the
digitigrade dog is adapted for high jumping and for great
speed.
Key words:
Biomechanics - hind limb - dog - horse - muscles -
digitigrade - unguligrade
I. INTRODUCTION
During locomotion the limbs are used for support and
also as levers for propulsion: the feet exert forces
upon the ground and reactional forces push the body
forward.
The intrinsic forces are produced by muscles which
stabilize the limbs during the support phase and move
the joints during the swing phase. Articular friction
is negligible, but some energy is spent in overcoming
the specific stiffness of the materials of the loco-
motory apparatus. The external forces acting upon
animal during progression are gravity, normal reaction
and friction between feet and ground, and inertia.
Since the speed is low, air resistance may be neglected.
Several authors have studied the structure and action
of the limbs by various methods (Badoux, 1964, 1970,
1972; Barclay, 1953; Gambaryan, 1974; Gray, 1944, 1956;
Hildebrand, 1960, 1965, 1968; Howell., 1965; Kimura et
al., 1972; Manter, 1938; Pratt et al'., 1976; Rooney,
1969; Tokuriki, 1973; Wentink, 1976, 1977, 1978).
From their work emanates the following picture of the
action of the hind limb.
During the first part of the support phase, the
principal external forces to be counteracted by muscular
action are gravity and ground reaction; they tend to
flex the joints of the hind limb and this is oppcsed by
the action of the extensor muscles: these muscles
transform the limb into a springy strut, which is
shortened by flexion of the joints towards the middle
of the support phase. As a consequence, the path
foliowed by the centre of gravity of the hind-quarters
flattens, which prevents waste of energy in vertical
movements. Moreover, the strut provokes a ground
reaction: the sense of its horizontal component
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(friction) is opposite to that of progression in the
first part of the support phase; this braking effect
is antagonized by the retractor muscles of the limb.
In the second part of the support phase, progression
and friction have the same sense; in this period
there is - during walk - no activity in the retractor
muscles. So the push-off at walk must be partly due
to the propulsive effect of the moment of the load
applied proximally to the inclined strut and to stored
tensile energy in the retractor muscles. The pitching
effect of the load is opposed by activity of the
protractor muscles which smoothes the jerky effect of
the external forces.
In the last part of the support phase, the projection
of the centre of gravity moves further away from the
point of support at the foot, which causes a decrease
of the relative magnitude of the vertical component of
the ground reaction; the horizontal component gains
in relative magnitude. After push-off, the limb swings
forward relative to the trunk and obtains a position
suitable for the following support phase. In the swing
phase the limb is shortened by flexion of the joints:
this brings the centre of gravity of the limb closer
to the pivot point at the hip. The initial acceleration
and subsequent deceleration of the limb during the swing
phase absorb the greater part of the energy spent at
locomotion. The closer the centre of gravity of the
limb is to the hip, the less will be the energy required
to swing the limb forward.
The aim of the present paper is to describe the role
of the muscles of the unguligrade (horse) and the
digitigrade (dog) hind limb and to interprete the
differences in anatomy with respect to the locomotory
abilities of the two types.
II. MATERIALS AND METHODS
Nine horses and ponies and seven Greyhounds with a
normal locomotion pattern were studied; specific
methods have been described in more detail in previous
papers (Wentink, 1976, 1977, 1978).
The horses walked (6 km.hr-J-) on the ground and were
filmed from the right side (exposure rate 125 frames per
second). The dogs walked (4.5 km.hr"-'-) on a moving belt
(exposure rate 125-250 frames per second): two of them
have also been filmed while walking on the ground
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(exposure rate 64 frames per second): no essential
differences were observed in the movements of the hind
limb segments in the two circumstances. Observations
on the kinematics are restricted to movement in a
sagittal plane.
The periods of muscular activity in the horses and
in the dogs walking on the moving beits were registered
using platinum wire electrodes. The activity was
assessed from the monitor screen and loudspeaker of a
DISA Electromyograph type 14 A 30, and embodied on a
tape recorder (Bell and Howell type VR 3200). Electro-
myographic studies were also made of two dogs walking
on the ground: no essential differences were observed
in the periods of muscular activity in animals walking
on the ground and on the moving belt.
After termination of the experiments the animals
were killed and embalmed with formalin. The limbs
were removed and divided into the segments thigh, shank
and cannon (table I). In the horses the centres of
gravity of the limb segments were determined by
suspending the segments at two different points in their
paramedian plane, in the dogs by twice balancing the
segments on a sharp rim, first perpendicular to and then
parallel with the long axes of the bones. The inter-
section of the two lines determines the centre of
gravity with sufficiënt accuracy.
The resultant of all forces applied at the centre of
gravity of each limb segment is F ; it is composed of
gravity (F ), ground reaction (F ), and muscular forces
(F ):            g
m                  F=F+F+F                                        (1)
g         n+w         m
The force F follows from
F*r = m.a                                                              (2)
The acceleration (a) of the centres of gravity in the
horizontal (X) and vertical (Y) directions can be derived
frcm:
(3), and
v =
dt
~ _ dv                                                                       f, \
a = —                                                              (4)
The acceleration is given for the middle of each of the
time intervals initially chosen.
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The limb segments rotate relative to each other,
whilst the centres of rotation (pivot points at the
joints) move with respect to the earth. The resulting
rotational moment (M ) is the sum of the moments of the
r                                    ...
forces about the pivot points at the joints, i.e.
gravity (M ), ground reaction (M ), inertia (M.) and
i g ï f-M \                              n+w                                x
muscular moment (.M ) :
m
(5),
M + M. + M =
n+w 1 m
1.(3
M
M
in which I is the moment of inertia and 13 the
angular acceleration in radians.sec" , which is derived
from the changes of the joint angles per unit of time:
de
dt
(6)
ü> =
?- d<J
(7)
dt
Fig. 1
The inclination ( a ) of the mechanical axis (solid lines;
length 1 ) of the limb shortly after placing and shortly before
lifting in the horse (A) and the dog (B). I represents the
sense of the horizontal inertia (in fact the force of the
acetabulum on the femoral head, called in the text the
force F ).
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The angular accelerations are given for the middle of
the time intervals initially chosen.
III.RESÜLTS
The results are given in the tables and in figures
1 to 5 inclusive. Complete descriptions of the cycles
of a stride of both horse and dog have been published
previously (Wentink, 1976, 1977, 1978); in the present
report attention is focused on the similarities and
differences in the kinematics and muscular actions
between the two types.
In the horse the fetlock hyperextends at placing and
the metatarsus initially moves backwards. Stretching
of the interosseus and the digital flexor tendons
stores elastic energy. In the dog the toes are placed
flat on the ground.
In the first part of the support phase the resultant
of friction and normal reaction at the hoof (foot), and
the resultant of FT (fig.1) and gravity at the hip exert
flexing moments about stifle and hoek joints. These
joints are stabilized by the action of the quadriceps
muscle (fig. 4) (rectus femoris in the horse, the vastus
group in the dog), and by the action of the gastrocnemius,
the superficial and deep digital flexor muscles: the limb
Fig.2
Accelerations of thigh (a), shank (b) and^cannon (c) in the
horse (A) and the dog (B)at walk in the horizontal (X; solid
lines) and vertical (Y; broken lines) directions
Positive values represent accelerations with a forward (x) or
upward (Y) sense, negative values represent accelerations with
a backward (X) or downward (Y) sense.
The periods of muscular activity are given below.
1.  protractor muscles (horse: M. tensor fasciae latae; dog:
M. tensor fasciae latae and M. sartorius).
2.  cranial hamstrings (inserting on the thigh and at the
stifle) and M. gluteus medius.
3.  caudal hamstrings (inserting' on the shank).
4.  M. vastus lateralis.
5.  M. rectus femoris.
6.  M. gastrocnemius.
7.  M. tibialis cranialis.
The support phase is indicated by the solid line at the
bottom.
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m.sec"
support          I swing 1__
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is transforraed into a springy strut which supports the
body and acts as a lever (fig. 5).
In the first part of the support phase stifle and
hoek flex in both horse and dog. However, in the horse
the stifle continues to flex throughout the support
phase; in the dog it is kept at an almost constant
angle after some initial flexion. In both types, but
especially in the horse, the hoek extends in the second
part of the support phase. Flexion of stifle and hoek
in the first part of the support phase and extension of
the hoek in the last part flatten the path foliowed by
the centre of gravity of the hind quarters, so that no
energy is wasted in vertical movements. Propulsion of
the body by the retraction of the hind limb in the first
part of the support phase is opposed by the forces in
the vertical direction (normal force and gravity),
forming a couple which tends to turn the right hind limb
anticlockwise when viewed from the right side; moreover,
rad.sec2
b 0
Fig. 3
Angular accelerations at the hip (a), stifle (b) and hoek
(c) in the horse (A) and the dog (B). Positive values
represent angular accelerations with an extending effect,
negative values represent angular accelerations with a
flexing effect. The support phase is indicated by the
solid line.
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the sense of progression and friction are opposite.
The retractors of the limb (medial gluteal and ham-
string muscles) antagonize the retarding forces, extend
the hip and produce the first top in the graph of the
horizontal acceleration (fig. 3).
After the middle of the support phase the couple of
vertical forces turns the right hind limb clockwise and
promotes extension of the hip. Activity ceases in the
retractor muscles and begins in the protractor muscles
(tensor fasciae latae muscle in the horse, rectus
femoris muscle in the dog). In this period, the
friction in the sense of progression of the animal
reaches its maximal value (Kimura et al., 1972; Pratt
et al., 1976). Hence the friction in this period of
the cycle must be due to the pitching effect of the load
(supported by the hind limb acting as an inclined
strut) , which produces the second top in the graph of
the horizontal acceleration. In man, a similar
progressive effect of the load (gravity) is described
by Elftman (1966). The antagonizing effect of the
activity in the protractor muscles smoothes the other-
wise jerky propulsion.
At placing, flexion of the joints by the action of
the external forces is opposed by muscular activity.
The moments of the muscles about the joints cause an
increase in the initially negative angular accelerations
(fig. 4).
At the end of the support phase - when the forces in
the horizontal direction have grown in relative impor-
tance, and hoof and toes still are flat on the ground -
there are evident differences in the positions of the
hind limb segments of the two types. The femur never
passes the vertical in the horse, but does so in the
dog; the tibia of the horse remains in a more vertical
position when compared with that in the dog; the cannon
in the horse passes beyond the vertical, while in the
dog it remains almost vertical (fig. 1).
Further, the active muscles are different: the tensor
fasciae latae and cranial tibial muscles in the horse,
the rectus femoris and superficial flexor muscles in
the dog (fig. 2).
To achieve stability at the end of the support phase,
the resultant of all forces acting upon the limb segments
must pass through the pivot points at the joints (fig.5).
In the dog (fig. 5B) , the resultant (R.. ) of the
ground reaction and the force exerted by the digital
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flexor muscles passes through the pivot point of the
metatarsophalangeal joint (considering the digits as a
single unit). The resultant (R0) of the force (F )
2_                                               C .
between the distal ends of the metatarsal and sesamoid
bones, provoked by the action of the interosseus muscle,
and R.. passes through the pivot point at the hoek.
The resultant (R„) of the reactional force (F ) between
Jj                                                                            3.
talus and tibia, provoked by the action of the crural
part of the superficial digital flexor muscle using
the metatarsus as a lever, and R passes through the
pivot point at the stifle.
In the horse, there is a comparable situation in the
distal phalangeal and fetlock joints (Badoux, 1972):
the resultant (R ) of the ground reaction (F,) and the
force of the digital flexor muscles (Ff) passes through
the pivot point of the fetlock, and the resultant (R )
of the elastic force in the interosseus tendon (F )
and R-. passes through the pivot point of the hoek (fig.
5). The position of the crural part of the superficial
digital flexor tendon relative to the position of the
cannon makes it almost impossible for this muscle -
provided this muscle could contract - to use the cannon
as a lever; hence in the horse, R is the resultant of
the force (F ) in the cranial tibial muscle and the
peroneus tercius tendon, and of R which passes through
the pivot point at the stifle.
•ff*
ff-*—-
Fig. 4
Electromyograms of the quadriceps muscle of the horse (A)
and the dog (B) at walk.
1.  M. vastus lateralis.
2.  M. rectus femoris.
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Fig. 5
Schematic representation of the sense of the forces applied
at the joints of the horse (A) and the dog (B) at placing
(a) and at the end of the support phase (b). (For
explanation see text).
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Table I
Relative lengths and weights of the hind limb segments in
4 horses and 4 Greyhounds. The relative weights are
expressed in percentages of the total weight (100 %) of
the hind limb. The relative lengths of the segments are
expressed in percentages of the sum (100 %) of the lengths
(1) between the caudal part of the greater trochanter and
the lateral epicondyl of the femur, (2) the lateral tibial
condyle and lateral styloid process, and (3) the proximal
and distal ends of the cannon.
Horse                          Dog
weight
71 + 4.6 %
74 + 0.8 %
19 + 3.4 %
18 + 1 %
6 + 1.3 %
4 + 0.5 %
10 + 1.3 %
8 + 0.6 %
thigh
shank
cannon
digit
cannon + digit
length
thigh                                                  41+2.5% 41 + 1.5 %
shank                                                  32 + 1.4 % 42+1 1
cannon                                                27 + 1.7 % 17 + 1.4 %
R is the resultant of the force (F ) by which the
patella is pressed against the femoral^trochlea - a
force exerted by the action of the lateral vastus muscle
in the horse, by the rectus femoris muscle in the dog -
and of R , which passes through the pivot point at the
hip.
At the end of the support phase, the sense of the
angular accelerations becomes negative (fig. 3); at
hip and hoek this is promoted by muscular actions, at
the stifle however, muscular activity has an opposite
effect. This difference in the effect of the muscular
moments about hip and hoek on the one hand, and about
the stifle on the other, is easily explained by the
fact that the flexor aspect of hip and hoek is on the
cranial side of the limb whilst the flexor aspect of
the stifle is on the caudal side.
In the swing phase the limb is shortened by flexion
of stifle and hoek. This brings the centre of gravity
of the limb closer to the pivot point at the hip and
72
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Table II
Percentage of the cycle of a walking stride at which
the long axes of the limb segments are in the extreme
retracted or protracted position.
d
3g
maximal
maximal
retraction
protraction
60 %
95 %
75
100
70
5
horse
maximal maximal
retraction protraction
thigh 55 % 95 %
shank 60 100
cannon 55                    90
thus reduces the moment of inertia about this joint.
Protraction is initiated by the action of the tensor
fasciae latae muscle; in the dog, and probably also
in the horse, by the action of the sartorius and
iliopsoas muscles. Flexion of the stifle at lifting
is the result of the combined effect of inertia and
muscular actions. The caudal hamstrings (which insert
on the tibia) lift shank and foot, hence they counter-
act the action of gravity and centrifugal force. The
more vertical position of the tibia at the end of the
support phase in the horse increases the relative
contribution of inertia to the total moment about the
stifle in comparison with the situation in the dog.
Activity was consistently registered only in the caudal
part of the biceps femoris muscle in the horse, but in
all muscles of the caudal hamstring group in the dog
in almost every stride.
The hoek is flexed by release of elastic strain
energy stored in the peroneus tertius tendon and by the
action of the cranial tibial muscle both of which
oppose the effect of inertia about the hoek joint. In
the first part of the swing phase, the angular
accelerations of the limb segments increase in spite of
the activity in the flexor muscles. This phenomenon
may be explained by the effect of inertia and by the
moment of gravity of shank and foot about the stifle.
At the end of the swing phase the length of the limb
increases. At hip and hoek, the effect of inertia
is opposed by the action of the extensor muscles, and
at the stifle by the action of the flexor muscles. In
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the last part of the swing phase the limb is prepared
for the impact at landing by simultaneous activity
in flexors and extensors of stifle and hoek, and
retraction begins as a result of the action of the
middle gluteal and hamstring muscles. In spite of the
activity in the extensor muscles, the angular
accelerations at hip and hoek become negative (fig. 3)
due to the effect of inertia. The angular acceleration
at the stifle becomes negative by the action of the
caudal hamstrings which oppose the inertia of shank and
foot about the stifle joint. The difference in the
effect of the muscular moments about hip and hoek on
the one hand and about the stifle on the other may be
explained by the different positions of the flexor
aspects of the joints with respect to the sense of
the effect of inertia.
IV. DISCUSSION
In walk, muscular activity primarily opposes the
effect of external forces : it stops when the effect of
the external forces contributes to progression. At the
end of the support and swing phases muscles control
pitch and swing: they smooth both push-off and placing
of the limb. The effect of muscular actions on the
sense of the angular accelerations may depend on
the effect of the external forces.
The muscles of the hind limb can be divided into
extrinsic muscles (which originate from the skeleton
of the trunk) and intrinsic muscles (which have both
origin and insertion on the skeleton of the limb). The
intrinsic muscles can be subdivided in parallel-fibered
(on the cranial aspect of the tibia) and pennate muscles
(extensors of stifle and hoek, flexors of the digits).
Thé latter group, and the rectus femoris muscle which
also has a pennate structure, display activity during
part or all the support phase and stabilize the limb;
the former group is active during portions of the
swing phase.
The extrinsic muscles form a loop in which the limb
is suspended. The caudal part of this loop displays
activity at the end of the swing phase and during the
first part of the support phase; it decelerates the
swing and propels the body in the support phase. The
cranial part of the loop is active in the first part of
the swing phase and protracts the limb; the caudal
74
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hamstrings are also active in this period and - in
unison with the muscles on the cranial aspect of the
tibia - they bring the centre of gravity of the limb
closer to the pivot point at the hip. The extrinsic
muscles (parallel-fibered) and the muscles on the
cranial aspect of the tibia are prime movers, while the
pennate muscles are stabilizers, i.e.they transform the
limb into a springy strut during the support phase.
In the first part of the support phase, the moment
of the force F (i.e. the horizontal inertia acting at
the hip) about the foot provokes in both types a tensile
stress at the plantar aspect of the tibia and a com-
pressive stress at its cranial side (fig. 1). In this
period the activity in the gastrocnemius muscle may
centre the line of action of the load on the tibia.
This is in accordance with the calculations of Badoux
(1970) for a statical situation.
The most crucial phenomenon to be explained is the
difference in dynamics between horse and dog at the end
of the support phase. In this period of the cycle the
relative magnitude of the moment of Fj about the foot
increases; this moment follows from (fig. 2):
M = F . 1 . sin a                             (7)
Since 1 and a , as well as the mass are grater in the
horse than in the dog, the effect of inertia is greater
in the former. In the horse, the muscles active at the
end of the support phase are located on the cranial
aspect of the limb and therefore are able to oppose the
effect of inertia. The moment of F about the foot
induces at this time a tensile stress on the cranial
aspect of the tibia and a compressive stress on its
caudal aspect: this effect is more pronounced in the
horse than in the Greyhound. In the horse, the activity
of the cranial tibial muscle centres the line of action
of the load on the tibia in the last part of the support
phase. When considering the anatomical differences
between horse (unguligrade) and dog (digitigrade), the
substitution of muscles by tendinous structures in the
horse is remarkable: the interosseus, the superficial
digital flexor, and the analogon of the peroneus longus
(peroneus tertius) are all tendinous in the horse but
muscular in the dog.
When comparing the locomotory abilities of horse and
dog, it must be kept in mind, however, that the muscular
strength in the horse is relatively less, due co the less
75
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favourable ratio between body mass and muscular cross
section.
In the horse, the superficial digital flexor and
interosseus tendons are stretched at placing and
consequently they store elastic strain energy. After
the middle of the support phase, this stored energy
contributes to the lift of the fetlock and the cannon:
the hoek extends and the stifle flexes. The inverse
angular movements of hoek and stifle passively extend
the peroneus tertius tendon; this also leads to storage
of elastic energy, which is used to flex the hoek when
lifting the limb (table II).
During the swing phase, stifle and hoek are initially
flexed and then extended in unison: substitution of
muscular tissue by tendons with the same potential
function, i.e. to flex and to extend the hoek, saves
energy. Further, both angular acceleration and swing
of the hind limb are smaller in the horse than in the
dog, which also saves energy (Hildebrand, 1960): the
horse is an animal built for great stamina and is a
stayer (Gambaryan, 1974).
In the digitigrade animal (dog) the interosseus and
superficial digital flexor muscles dig the toes and
claws in the ground and this provides a strong grip.
The coëfficiënt of friction between the pads of a dog
and the ground is greater than that between the hoof of
a horse and the ground (Badoux, 1964), so that in
digitigrade animals the forward impulse can be relatively
greater than in unguligrades. Dogs may clear obstacles
of two metres or more; horses are able to jump less
high in comparison with the dog. The greater friction
promotes a more vigorous push-off and a potentially
greater speed: the fastest land going animal is the
digitigrade cheetah, a well-known sprinter.
REFERENCES
Badoux, D.M. : Friction between feet and ground. Nature 202,
266-267 (1964).
Badoux, D.M. : The statical function of some crural muscles
in the horse. Acta Anat. 75, 396-407 (1970).
Badoux, D.M. : Biomechanics of the autopodium of the equine
hind leg. Koninkl. Nederl. Akademie van Wetensch. 75C,
224-242 (1972).
Barclay, 0. : Some aspects of the mechanics of mammalian
locomotion. J. Exp. Biol. 30, 116-120 (1953).
76
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Elftman, H. : Biomechanics of muscle. J. Bone and Joint
Surg. 48A, 363-377 (1966).
Gambaryan, P.P. : How mammals run. New York - Toronto:
John Wiley and Sons (1974).
Gray, J. : Studies in the mechanics of the tetrapod
skeleton. J. Exp. Biol. 20, 88-116 (1944).
Gray, J. : Muscular activity during locomotion. Brit. Med.
Buil. 12, 203-209 (1956).
Hildebrand, M. : How animals run. Sci. Amer. 5, 148-157
(1960).
Hildebrand, M. : Symmetrical gaits of horses. Science 150,
701-708 (1965).
Hildebrand, M. : Symmetrical gaits of dogs in relation to
body build. J. Morphol. 124, 353-360 (1968).
Howell, A.B. : Speed in animals. New York : Hafner (1965).
Kimura, T., Endo, B. : Comparison of force of foot between
quadrupedal walking of dog and bipedal walking of man.
J. Fac. Sci. Uni. Tokyo 5, 119-130 (1972).
Manter, J.T. : The dynamics of quadrupedal walking. J. Exp.
Biol. 15, 522-540 (1938).
Pratt, G.W., 0'Connor, T. : Force plate studies of equine
biomechanics. Amer. J. Vet. Res. 37, 1251-1255 (1976).
Rooney, J.R. : Biomechanics of lameness in horses.
Baltimore : The Williams and Wilkins Company (1969).
Tokuriki, M. : Electromyographic and joint mechanical studies
in quadrupedal locomotion. I. Walk. Jap. J. Vet. Sci.
35, 433-446 (1973).
Wentink, G.H. : The action of the hind limb musculature of
the dog in walking. Acta Anat. 96, 70-80 (1976).
Wentink, G.H. : Biokiretical analysis of hind limb movements
of the dog. Anat. Embryol. 151, 171-181 (1977).
Wentink, G.H. : Biokinetical analysis of the movements of the
pelvic limb of the horse and the role of the muscles in
walk and trot. Anat. Embryol. 152, 261-272 (1978).
77
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-ocr page 81-
AN EXPERIMENTAL STUDY ON THE ROLE OF THE RECIPROCAL
TENDINOUS APPARATUS OF THE HORSE AT WALK.
G.H. WENTINK
Institute of Veterinary Anatomy, State University Utrecht.
SUMMARY
The locomotor pattern of the hind limb of seven horses
has been studied in intact animals and after transection
of the following structures: the peroneus tertius tendon,
the cranial tibial muscle, both cranial tibial muscle and
peroneus tertius tendon, and the superficial digital
flexor tendon. The investigation was carried out by high
speed cinematography and electromyography. It is concluded
that (1) the muscles and tendons over the cranial aspect of
the tibia play an important role during the support phase;
(2) the movements of the hind limb can be performed
without the action of the cranial tibial and gastrocnemius
muscles; (3) the tendons in the shank store elastic
energy during the support phase; (4) the gastrocnemius
and cranial tibial muscles may centre the force of the load
through the long axis of the tibia.
Key words:
Biomechanics - hind limb - reciprocal tendinous apparatus
- locomotion - horse.
I. INTRODUCTION
The function of the superficial digital flexor and
the peroneus tertius tendons - denoted as the recipro-
cal tendinous apparatus - has been explained by
several authors (Bradley and Grahame, 1946; Grau, 1943;
Seiferle, 1968; Sisson, 1975) as a part of the
mechanism that enables the horse to remain standing
with a minimum of muscular effort.
Badoux (1970) calculated the effect of a force
developed by the gastrocnemius muscle, counteracted
by the peroneus tertius tendon. The action of this
muscle centres the line of action of the load through
the long axis of the tibia in a statical situation.
In a previous paper the action of the tendons of
the reciprocal tendinous apparatus were described as
elastic strands (Wentink, 1978a). So far as the
elastic properties of these tendons are
79
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concerned, it may be noted that Alexander (1977a;1977b)
calculated the elastic strain energy for tendons
(2,000 - 9,000 J.kg'1) and pointed to the importance
of storage of elastic strain energy in tendons during
locomotion. In this respect, Hildebrand's (1960)
statements are of value; he pointed to the amount
of energy that is spent in accelerating and decelerating
the limbs during the swing phase. The synchronisation
of the movements of stifle and hoek during the swing
phase is a consequence of the action of the reciprocal
tendinous apparatus. Strubelt (1928), however, does not
mention any consequences on the locomotor pattern of
the hind limb after transection of either the peroneus
tertius or the superficial digital flexor tendon.
Previous papers (Wentink, 1978a; 1978b) dealt with
the role of the muscles of the hind limb. In this
paper the locomotor pattern of the hind limb at walk
is described for horses with intact and with transected
tendons.
II. MATERIALS AND METHODS
The experiments were performed with seven horses and
ponies, three of which were included in a previous
study (Wentink, 1978a, horses I, Il'and III). In four
horses the peroneus tertius tendon was transected about
10 cm above the hoek joint; in a fifth horse the
cranial tibial muscle was transected at the same level.
After filming the locomotion of these operated animals,
the peroneus tertius in the latter horse, and the
cranial tibial muscle in one horse of the former group
were also cut. In two additional horses the superficial
digital flexor tendon was transected about 10 cm above
the level of the calcaneus. The operations were per-
formed under general anaesthesia.
The animals were filmed from the right lateral side
after marking of the skin over the skeletal points
(exposure rate 110 to 150 frames per second). The
analysis of the movements is restricted to the sagittal
plane. The attention was fpcused primarily upon the
relation between the accelerations of the centres of
gravity of the three segments and upon the relation
between the changes of stifle and hoek during a stride.
In unoperated animals these relations were fairly
constant although differences occurred between consecu-
tive strides of a single horse and between various
80
-ocr page 83-
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-ocr page 84-
phase must be ascribed to the deep digital flexor,
since activity in the gastrocnemius muscle is lackirig
in this part of the cycle, even after transection of
the superficial digital flexor tendon. The superficial
digital flexor and the interosseus tendons store
elastic energy on impact and this is subsequently used
to promote the simultaneous vertical acceleration of
cannon and shank at the end of the support phase. The
diminution of these accelerations after transection of
the superficial digital flexor tendons stresses the
role of this tendon in the upward accelerations of
these segments and of the trunk (fig. IC).
The distal pull of the superficial digital flexor
tendon causes a negative angular acceleration at the
stifle; the quadriceps muscle hardly opposes flexion
of this joint. Transection of this tendon cancels the
rotation of the femur and enables the quadriceps muscle
to extend the stifle in the last part of the support
phase, a phenomenon observed in all strides after
operation (fig. 2C; Table I, C).
A compensatory decrease in the activity of the
quadriceps muscle may be responsible for the reduction
of the angular acceleration at the stifle during impact
and for the decrease of the horizontal acceleration of
the centre of gravity of the thigh in the first part of
Fig.1
Accelerations in the horizontal (X) and vertical (Y) direc-
tions of the centres of gravity of the thigh (a), the
shank (b) and the metatarsus (c) before and after experi-
mental surgery. The abnormal and normal situation for each
individual have been compared. Each curve represents one
stride selected on the cinematographical performance.
Positive values represent accelerations with a forward (X)
or upward (Y) direction, negative values a backward (X) or
downward (Y) direction.
The solid horizontal bar indicates the support phase.
A : Before (5,8 km.h ; 1) and after transection of the
peroneus tertius tendon (5,5 km.h"1; 2).
B : Befoee (5 km.h~l; 1), after transection of the cranial
tibial muscle (4,5 km.h"-'-; 2) and after transection of
both cranial tibial muscle and the peroneus tertius
tendon (4,2 km.h-1; 3).
C : Before (6,9 km.h~l; 1) and after transection of the
superficial digital flexor tendon (5,1 km.h"-'-; 2).
82
-ocr page 85-
83
-ocr page 86-
the support phase (fig. IC); the latter phenomenon
was observed in all strides after operation, but also
in two strides of an unoperated horse.
The opposite angular changes at stifle and hoek in
the second half of the support phase stretch the peroneus
tertius tendon. Transection of this tendon results in
a decrease of the angular acceleration at the stifle
in the first part of the support phase (fig. 2A) , and
in a change of the pattern of the forward acceleration
of the centre of gravity of the thigh in all strides
of the operated animals (fig. IA).
This can be readily explained by the fact that now
the caudal pull of the superficial digital flexor
tendon is not counteracted by the peroneus tertius
tendon. In the last part of the support phase the
stifle is extended by the action of the quadriceps
muscle.
The positive angular acceleration of the hoek joint is
prolonged, which causes an overextension of this joint,
partly balanced by the cranial tibial muscle. Tran-
section of this muscle alone hardly interferes with
the angular changes of the hoek joint; cutting the
peroneus tertius tendon and the cranial tibial muscle
enables the superficial flexor tendon to extend the
hoek maximally (table IB, fig. 1B, 2B). Extension of
the hoek, leads in the absence of a simultaneous for-
ward movement of the thigh to an initial increase and
subsequent decrease of the horizontal acceleration of
the centres of gravity of cannon and shank (fig. IB).
Thus, transection of the cranial tibial muscle and the
peroneus tertius tendon severely disturbs the pattern
of the acceleration of the centres of gravity of the
limb in the horizontal direction; the acceleration in
Fig.2
Changes in the angles of stifle and hoek, and in the angular
accelerations before and after experimental surgery. The
average of three abnormal and three normal strides are
compared for each animal; a denotes the stifle, b the hoek
joint. Positive values represent an extending, negative
values a flexing angular acceleration.
The solid horizontal bar indicates the support phase.
Further legends see figure 1.
84
-ocr page 87-
joint
angle
\J
\y
s\
t\
/F
/\
\ /
rad.sec-2
50 H
+
a 0
A
C\
/1
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K
V
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M
i
50
l/W
\
fV
+
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^v
^
\U
.XH
y
50 J/
85
-ocr page 88-
the vertical direction does not deviate much from the
normal situation (fig. 1B) . This experiment confirms
the important role of the peroneus tertius tendon and
the cranial tibial muscle during the support phase.
Flexion of the stifle and hoek occurs simultaneously
at the end of the support phase. Transection of the
cranial tibial muscle affects neither the moment of
flexion of the hoek (fig. 2B), nor the moment at which
the cannon overtakes the shank (fig. 3B). Cutting the
peroneus tertius tendon causes flexion of the hoek to
lag slightly behind that of the stifle (fig. 2A,
table IA) and the moment at which the cannon overtakes
the shank is also delayed (fig. 3A). In this situation
flexion of the hoek joint depends on muscular activity
alone. Transection of both the cranial tibial muscle
and the peroneus tertius tendon makes flexion of the
hoek almost impossible. The initial flexion in the
first part of the swing phase is passively brought
about by the weight of the cannon. The movements of
the cannon are then determined by the acceleration of
the shank and the increased flexion of the stifle. The
shank is decelerated in the middle of the swing phase
and the inertia of the cannon leads to a jerky flexion
of the hoek (fig. 1B, 2B, table IB). Transection of the
superficial digital flexor tendon prolonges flexion of
the stifle and hoek in the swing phase and also reduces
the downward accelerations of shank and cannon (fig. IC;
table IC).
Fig.3_
Velocities of the centre of gravity of the thigh, the shank
and the metatarsus in the horizontal (X) direction of a
normal limb (Al) compared with those in the same limb after
transection of the peroneus tertius (All), in another
normal horse (BI) compared with those of the same limb
after transection of the cranial tibial muscle (Bil) and
after transection of both the peroneus tertius tendon and
the cranial tibial muscle (BIIl) .
The solid bars indicate the support phase.
The extreme percentages of the cycle of a stride at which
the cannon overtakes the shank are (all strides have been
recalculated to a support phase of 60 %):
AI : 54-59 %; All : 62-63 %; BI : 57-58-%; Bil : 56-60 %;
BUI : 61-72 %.
86
-ocr page 89-
/'
m.sec"1
4
-
r\
-Bi / \
II Yi
\
/
\
A' l.........,M
I
\
oJy
4 -
-
All
1
/ \
\
\
0
: f----
\l--
rj
X
1
Bil
/ \
/
n.
i
/■
............thigh
_____ shank
_____ cannon
Bui
A
u
ij-
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-ocr page 90-
00                                                                   TABLE I
00
Extreme values of the changes of the angles of stifle and hoek joints Cfig. 2). The amount
of changes is given for three horses before and after experimental surgery.
Support
phase
Swing ph
ase
Fl(
ïxion
Extension
Flexion
Extension
degrees
period
degrees
period
degrees
period
degrees
period
14-23
0-42%
0
42-51%
22-28
51-75%
36-48
75-100%
14-20
0-36%
0-1
36-48%
21-26
48-71%
35-44
71-100%
9-16
0-11%
22-25
11-51%
44-48
51-77%
32-41
77-100%
6-12
0-11%
28-30
11-51%
44-47
51-78%
22-29
78-100%
Stifle joint before*
after transection
of the per. tert.
Hoek joint before
after transection
of the per. tert.
0
0
16-
■17
52-
■82%
33-
■35
82-
-100%
3-
-7
36-
■52%
20-
■25
52-
■78%
26-
■36
78-
-100%
0-
■8
34-
■52%
25-
•36
52-
■76%
34-
■43
76-
-100%
17-
■19
10-
■53%
42-
■44
53-
■83%
30-
■35
83-
■100%
17-
■27
10-
■52%
43-
■47
52-
■82%
27-
■31
82-
■100%
Stifle joint before                          17-18 0-52%
after transection
9-18 0-36%
of the cran.tib.
after transection
of the cran.tib.m.                               9-17 0-34%
and per. tert.
Hoek joint before                                 7-8 0-10%
after transection
1-12 0-10%
of the cran.tib.m.
after transection
of the cran.tib.m.                                1-8 0-16% 25-28 16-47%                            The cannon pendulates
and per. tert.
C.
0
47-55%
21-23
55-71%
35-39
71-100%
1-4
43-54%
18-23
54-76%
32-38
76-100%
23-29
9-52%
39-44
52-76%
30-32
76-100%
20-23
21-54%
38-43
54-80%
29-37
80-100%
Stifle joint before                          13-15 0-47%
after transection
13-19 0-43%
of the sup.dig.fl.
Hoek joint before                               11-17 0-9%
after transection
13-16 0-21%
of the sup.dig.f1.
In horses A and C the angle of the stifle joint is
constant during a part of the support phase, whilst
in horse B flexion is continued throughout the support
phase.
-ocr page 91-
IV. DISCUSSION
Both support and swing phase are affected by
transection of either the peroneus tertius or the
superficial digital flexor tendons. This is in contra-
diction with the results of Strubelt (1928) and may be
explained by the fact that the used, rather aged
horses were reluctant to move.
Transection of the cranial tibial muscle causes an
initial increase and subsequent decrease of the
acceleration of the centre of gravity of the shank at
the end of the support phase.
At placing, the superficial digital flexor and
interosseus tendons are stretched by the body weight and
store elastic energy. When released, the elastic energy
assists in lifting cannon and shank by flexion of the
fetlock joint and extension of the hoek joint. The
distal pull of the superficial digital flexor tendon
leads to flexion of the stifle joint, to stretching of
the peroneus tertius tendon and thus to storage of
elastic energy in preparation for flexion of the hoek
joint at the end of the support phase
The gastrocnemius and cranial tibial muscles assist the
action of these tendons. In this context, mention may
be made of the calculations of Alexander (1977b) who
demonstrated that the elastic energy stored in the
tendons of the antilope hind limb makes a considerable
contribution to locomotor performance. Some authors
(Chassin et al., 1976; Hildebrand, 1960) argue that
most energy spent at locomotion is used to accelerate
and decelerate the limbs during the swing phase.
Alternate stretching of the tendons óf the reciprocal
tendinous apparatus during the support phase stores
energy, which is made available in the subsequent
swing phase. Such a mechanism economizes energy during
locomotion. Equids are of course well known as
"stayers".
In the dog, a digitigrade animal lacking the recipro-
cal tendinous apparatus, the activity of the muscles over
the caudal aspect of the tibia is restricted to the
support phase, and that of the muscles over the cranial
aspect to the swing phase (Tokuriki, 1973; Wentink,
1976). Hence there is a clear difference between the
unguligrade horse and the digitigrade dog with respect
to the coordination and the use of the crural muscles,
especially at the end of the support phase. Moreover,
89
-ocr page 92-
in the dog the movements of the distal segment are per-
formed by energy-consuming muscular action, while in the
horse the tendons of the reciprocal tendinous apparatus
make an appreciable contribution to the movements.
From the foregoing analysis it appears that movements
of the hind limb of the horse may be performed without
participation of the gastrocnemius and cranial tibial
muscles. The movements of the thigh are primarily induced
by the extrinsic muscles originating from the pelvis and
inserting on femur and tibia which form a muscular loop in
which the limb is suspended (Wentink, 1977; 1978a). The
movements of the stifle are transmitted to the hoek joint
by the tendons of the reciprocal tendinous apparatus. With
a view to the limited contribution of the gastrocnemius and
cranial tibial muscles to the limb dynamics on the one side
and their impressive mass on the other, it is reasonable to
assume that these muscles play a role in centering the line
of action of the load on the tibia during the support phase
(Badoux, 1970; Wentink, 1978a). In vivo bone strain
measurements of the tibia which may support this assertion
are in hand.
REFERENCES
Alexander, R. McN., Bennet-Clark, H.C. : Storage of elastic
energy in muscle and other tissue. Nature 265,
114-117 (1977a).
Alexander, R. McN.: Allometry of the limbs of antilopes
(Bovidae). J. Zool., Lond. 183, 125-146 (1977b).
Badoux, D.M. : The statical function of some crural muscles
in the horse. Act. Anat. 76, 396-407 (1970).
Bradley, O.C., Grahame, T. : The topographical anatomy of
the limbs of the horse, 2nd ed. Edinburgh: Green & Son
(1946).
Chassin, P.S., Taylor, CR., Heglund, N.C., Seeherman, H.J.:
Locomotion in lions: energetic cost and maximum aerobic
capacity. Zool. 49, 1-10 (1976).
Grau, H. : Das Muskelsystem. Der aktive Bewegungsapparat.
In: Ellenberger und Baum, Handbuch der Vergleichende
Anatomie der Haustiere (18th ed.) Berlin, Heidelberg,
New York : Springer Verlag 1943 (reprint 1974).
Hildebrand, M. : How animals run. Sci. Amer. 5, 148-157 (1960).
Seiferle, E. : Aktiver Bewegungsapparat, Muskelsystem. In:
Lehrbuch der Anatomie der Haustiere, Band I (ed.
R. Nickel, A. Schummer, E. Seiferle) Berlin, Hamburg:
Paul Parey, dritte Auflage (1968).
90
-ocr page 93-
Sisson, S. : Myology (Equine). In: Sisson and Grossman's
The anatomy of the domestic animals (ed. R. Getty),
5th ed. Philadelphia, London, Toronto: Saunders 1975.
Strubelt : Uber die Bedeutung des Lacertus fibrosus und des
Tendo femorotarseus für das Stehen und die Bewegung des
Pferdes. Arch. Tierheilk. 57, 575-585 (1928).
Tokuriki, M. : Electromyographic and joint-mechanical
studies in quadrupedal locomotion. Jap. J. Vet. Sci.
35, 433-446 (1973).
Wentink, G.H. : The action of the hind limb musculature of
the dog in walking. Acta Anat. 96, 70-80 (1976).
Wentink, G.H. : Biokinetical analysis of hind limb movements
of the dog. Anat. Embryol. 151, 171-181 (1977).
Wentink, G.H. : Biokinetical analysis of the movements of
the pelvic limb of the horse and the role of the muscles
in the walk and the trot. Anat. Embryol. 152,
261-272 (1978a).
Wentink, G.H. : Dynamics of the hind limb at walk in horse
and dog. Anat. Embryol. (submitted) (1978b).
91
-ocr page 94-
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BIOMECHANICS OF THE HIND LIMB OF
HORSE AND DOG
SYNOPSIS
1. Introduction
In this synopsis a visualization of the results is
presented in a pictorial survey. These results were based
on electromyography and cinematography; the available
technical facilities excluded the use of force plates,
so that data from literature concerning the sense of the
forces operating at the foot have been incorporated.
Electromyography reveals when muscles display activity
during a stride. However, it does not give information
whether a muscle contributes to a specific movement,
opposes it or is active merely to adjust its length to the
altered spatial position of its origin and insertion. In
combination with the kinematical data from the cinerecord
conclusions about the action of the muscles during the
cycle of a stride can be drawn.
The plate pictures in figure I a model with the schematic
representation of the bones and muscles; at left the hind
limb of the horse, at right that of the dog.
In figure II the effect of the external forces
applied at the femoral head (F, ) and at the foot (F ) is
visualized; these forces have flexing moments about
stifle and hoek joints and are opposed by intrinsic muscular
moments (M ). In figures III and IV the muscles which
display activity are drawn in a model of the skeleton in
the successive stages of the cycle of a stride, which
commences at the moment of placing of the foot and ends at
replacing for the following support phase (a, b and e
denote the beginning, the middle and the end of the support
phase, d and e the beginning and end of the swing phase).
Figure III shows the active muscles in the dog, figure IVA
those in the horse. In fig.IVB the stretching and shorteninj
of the tendons of the reciprocal apparatus is separately
given: stretching is given by the longer, shortening by the
shorter broken line.s.
In the lower figures V to VIII inclusive the effect of
transection of the tendons and of the cranial tibial muscle
is given: in the first pictures is indicated which structure
is cut.
A concept of the anatomical arrangement of the muscles of th'
hind limb is given fig. IX.
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Although the effects of the external forces acting on the
limb take place simultaneously, the corresponding function
of the muscles are dealt with separately.
Muscular actions
During the support phase flexion of stifle and hoek
(fig. II) is prevented by the actions of the extensor
muscles of these joints. The limb is then transformed
into a springy strut over which the body moves as over a
spoke. Dynamically speaking, the limb is used as a lever
to develop the push-off at the end of the support phase.
In both species the stifle joint is kept extended by the
action of the quadriceps muscle (fig. III and IV). In
the dog this is brought about by the lateral vastus, and,
in the second part of the support phase, by the action of
the rectus femoris muscle; in the horse initially by the
rectus femoris and in the second part by the action of
the lateral vastus muscle. This difference in the periods
of activity of the parts of the quadriceps muscle may be
explained by the locking mechanism of the stifle of the
horse: activity in the lateral vastus muscle at the end
of the support phase prevents hooking of the patella on
the medial ridge of the femoral trochlea by the lateral
rotation of the patella around its longitudinal axis.
In the dog (fig. III) the hoek joint is kept extended
by the muscles over the caudal aspect of the tibia:
initially by the combined action of the gastrocnemius and
superficial digital flexor muscles, in the last part of the
support phase by only activity of the latter muscle. The
deep digital flexor muscle may assist in the stabilization
of the hoek, but its main action is in unison with the
interosseus muscle to press the digits against the
ground and to provide strong grip.
In the first part of the support phase in the horse (fig.
IVA) activity is present in the muscles over the caudal
aspect of the tibia (gastrocnemius and deep digital flexor
muscles); in the last part of the support phase the
cranial tibial muscle comes into action and the activity
in the gastrocnemius ceases. The mechanical moments about
the hoek joint are now equilibrated by the deep digital
flexor and cranial tibial muscles.
There exists a remarkable difference between the digitigrade
dog and the unguligrade horse in the coordination of
activities in the crural muscles. This may be explained by
the positions of the shank and cannon in this particular
-ocr page 97-
part of the cycle: the inclination of the tibia with
respect to the vertical is greater in the dog than in
the horse. The metatarsus of the dog has an approximately
vertical position in this stage of the cycle when all
pads are in contact with the ground, while in the horse
the cannon always passes the vertical while the hoof is
still in contact with the ground. Data from force
plate studies suggest that in the horse the vector of
the resultant ground reaction passes through the hoek
joint, while in the dog it passes in front of the hoek
and thus has a flexor moment about this joint.
The limb is intrinsically stabilized and supports the
(partial) weight of the body. In the first part of the
support phase it acts as an inclined strut provoking
a friction with a sense opposite to the animal's
progression: the limb then opposes the forward movement
of the animal. The limb is retracted by the hamstring
and middle gluteal muscles (in the dog by the adductor
and gracilis muscles also); the effect of the inertia
of the body is complemented by the action of these muscles
in bringing the proximal end of the limb into a position
in which the dynamic effect of the weight provokes a
friction in the sense of the animals progression, which
is suitable for the push-off. At this moment, the
activity in the retractor muscles stops. The effect of
friction is smoothed by the protractor muscles (tensor
fasciae latae muscle and - in the dog - the rectus
femoris muscle) to prevent jerks in the progression.
In the swing phase the joints are flexed - the stifle by
the action of the caudal hamstrings, the hoek by the
action of the cranial tibial muscle assisted by the long
digital extensor muscle. The main action of the latter
is to extend the digit(s). The limb is protracted by
the tensor fasciae latae muscle, in the dog by the
sartorius muscle also.
At the end of the swing phase the forward movement of
the limb is checked by the action of the retractor muscles
of the limb and by the action of the extensors of the hoek
joint.
From this survey of the actions of the muscles it emerges
that the muscles of the hind limb can be divided into two
functional groups (fig. IX).
1. The muscles which transform the limb into a springy
strut during the support phase: these muscles are printed
in yellow. Their activity is restricted to the end of
the swing phase and to all or part of the support phase
95
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These muscles comprise the quadriceps group, the
gastrocnemius and the deep digital flexor muscles in
both species and the superficial digital flexor and the
interosseus muscles in the dog. These muscles have a
pennate structure, with the exception of the interosseus
muscle in the dog.
2. The extrinsic muscles of the limb and the muscles
over the cranial aspect of the tibia, printed in red.
These muscles are parallel-fibered. The extrinsic
muscles form a loop in which the limb is suspended: the
caudal part is active to check the forward swing of the
limb in the last part of the swing phase; in the first
part of the support phase it moves the body over the
stabilized limb and complements the effect of inertia.
The cranial part of this loop displays activity at the
end of the support phase. It smoothes the otherwise
jerky propulsion by the dynamic effect of the weight and
gives the limb a forward acceleration in the first part
of the swing phase. The stifle is then flexed by the
caudal hamstrings and the hoek by the muscles over the
cranial aspect of the tibia; flexion of these joints
brings the centre of gravity of the limb closer to the
hip and diminishes the moment of rotational inertia
about the pivot point. The muscles of this latter group
are prime movers of the limb, those of the former group
are stabilizers of the limb.
When considering the anatomical differences between
horse and dog, there is a remarkable "substitution" of
muscular tissue by tendinous analogues in the horse
(superficial digital flexor, interosseus and peroneus
tertius). In the dog the muscles help to dig the claws
into the ground, which results in a strong grip and a
forced push-off. Moreover, the coëfficiënt of friction
between the pads of a dog and the ground is greater than
that between the hoof of a horse and the ground, so that
in the digitigrade dog the forward impulse can be
relatively greater than in the unguligrade horse. Dogs
may clear obstacles of two metres or more and rely on
sudden sprints to capture prey animals.
The role of the reciprocal tendinous apparatus in the
horse
The effect of the load on these tendons is shown
schematically in figure IVA,
At placing (a), the interosseus and superficial digital
flexor tendons are stretched (long broken lines) by the
-ocr page 99-
impact and store elastic energy. This energy gives the
limb and the trunk a (mainly upward) acceleration in the
middle of the support phase. The pull of the superficial
digital flexor tendon at the femur flexes the stifle
during this phase. The opposite angular movements of
stifle and hoek stretch the peroneus tertius tendon which
in turn stores elastic energy (c): thus in a sense, the
elastic energy stored at impact is transfered from the
tendons over the caudal aspect to those over the cranial
aspect of the tibia. This energy is ultimately used to
flex the hoek in the last phase of the support phase when
the hoof starts rolling over.
The effects of transection of the above mentioned tendons
and of the cranial tibial muscle are given in figures V
to VIII inclusive: the solid models give the abnormal,
the interrupted models the normal situation.
3a) Transection of the superficial digital flexor tendon
(fig. V) diminishes the upward force operating at the
segments of the limb. The stifle extends at the end of
the support phase when the femur is relieved from the
distal pull of this tendon; flexion of the hoek joint is
prolonged during the support phase.
3b) Transection of the peroneus tertius tendon (fig. VI)
enables the extensor forces to extend the hoek at the
end of the support phase. This results in an irregular
pattern in the effect of the forces applied at the centres
of gravity of shank and cannon, a phenomenon also observed
after transection of the cranial tibial muscle (fig. VII)
as well as after transection of both structures over the
cranial aspect of the tibia (fig. VIII).
After eliminating the peroneus tertius tendon, flexion
of the hoek joint and the forward acceleration of the cannon
depend on muscular activity alone.
In the intact animal the cannon overtakes the shank in the
last part of the support phase; after transection of the
peroneus tertius tendon this effect is only seen in the
first part of the swing phase. This illustrates the role
of the latter tendon in the flexion of the hoek joint. In
the normal dog, flexion of the hoek merely depends upon
muscular activity and takes also place in the first part
of the swing phase.
3c) Transection of the cranial tibial muscle (fig. Vil)
does not influence the moment at which the cannon overtakes
the shank, but transection of both the peroneus tertius
tendon and the cranial tibial muscle (fig. VIII) severely
97
-ocr page 100-
disturbs the pattern of the movements of the cannon.
The delayed flexion of the hoek and the kink in the
Achilles tendon, described in the clinical literature
as occurring after peroneus tertius rupture, were seen
only after the latter operation.
The reciprocal tendinous apparatus plays a role in the
conservation of energy: the horse is a well-known stayer.
The limb can theoretically be moved by the extrinsic
muscles and then in the horse the angular changes of
the stifle joint are transmitted by the reciprocal
tendinous apparatus to the hoek joint. Hence, theoretically
the intrinsic movements of the hind limb of the horse
might be performed without the action of the gastrocnemius
and cranial tibial muscles (fig. X). These muscles
however, are active during that part of the cycle in
which the tendons over the same aspect of the tibia are
stretched. With an eye to the impressive mass of these
muscles, a complementory function is suggested, which is
pictured in fig. X.
At placing the effect of inertia provokes a tensile stress
over the caudal aspect of the tibia and a compressive
stress over its cranial side pictured by the broken line:
in this situation the line of action of the load may be
centered through the long axis of the tibia by the action
of the gastrocnemius muscle. At the end of the support
phase the effect of inertia is reversed and so a tensile
stress may be expected over the cranial aspect and a
compressive stress over the caudal aspect of the tibia
pictured by the broken line: in this situation the cranial
tibial muscle may centre the line of action of the load
through the long axis of the tibia.
98
-ocr page 101-
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7) in the horse flexion of the stifle is continued
throughout the support phase, while in the second part of
this phase extension of the hoek takes place; 8) the
subsequent stretching of the tendons of the reciprocal
apparatus during the support phase stores elastic energy,
which is ultimately used to flex the hoek joint; 9) the
muscular digital flexor muscles in the dog dig the claws
in the ground for strong grip and forced push-off; 10)
in the horse the metatarsus passes beyond the vertical
so that the cranial tibial muscle comes into action to
prevent overextension of the hoek joint; in the dog the
metatarsus remains in a vertical position at the end of
the support phase and the cranial tibial muscle does not
display activity; 11) in the horse the movements of the
hind limb might theoretically be performed without
activity in the gastrocnemius and cranial tibial muscles;
these muscles may centre the line of action of the load
through the long axis of the tibia. Bone strain analysis
is necessary to proof this assumption.
SAMENVATTING
Dit proefschrift beschrijft het onderzoek van enige
biomechanische aspekten van de bewegingen van het achter-
been van paard en hond, geconcentreerd op de rol van de
spieren van het crus binnen het spanzaag mechanisme.
Het achterbeen is verdeeld in de segmenten dij, schenkel
en pijp (bij de hond middenvoet en tenen); het gewicht
en het zwaartepunt van de segmenten zijn bepaald. De
kinematische gegevens zijn in filmbeelden opgemeten; de
periodes waarin de verschillende spieren aktiviteit ont-
plooien zijn met behulp van elektromyografie geregis-
treerd.
Uit deze gegevens is afgeleid welke bijdrage de ver-
schillende spieren aan de bewegingen van het been
tijdens de stap leveren, en welke koordinatie er bestaat
tussen spiergroepen. De interpretatie is gekorreleerd
met literatuurgegevens over de' krachten die de voet op
de grond uitoefent. Verschillen in het bewegingspatroon
van het achterbeen van paarden voor en na doorsnijden
van pezen van het spanzaagmechanisme hebben bijgedragen
tot het verkrijgen van inzicht in de dynamische betekenis
van deze pezen tijdens de stap.
Uit deze studie blijkt dat: 1) de spieren van het
achterbeen verdeeld kunnen worden in twee groepen: a)
bewegers (de extrinsieke spieren en de spieren gelegen
100
-ocr page 103-
aan de craniale zijde van de tibia), die hoofdzakelijk
aktief zijn in de zweeffase; b) stabilisatoren (de
strekkers van knie en sprong en de buigers van de tenen),
die in hoofdzaak aktief zijn gedurende de hele steunfase
of een deel ervan; 2) de broekspieren verdeeld kunnen
worden in een craniale (die aan de dij insereert) en een
caudale (die aan de schenkel insereert) groep; beide
spiergroepen strekken de heup tijdens de steunfase, de
laatstgenoemde buigt de knie in de zweeffase; 3) het
aantal aktieve spieren het grootst is bij het neerzetten
en bij het optillen van het been; 4) tijdens de stap
de spieren aktief zijn om de (externe) krachten tegen te
werken; zodra deze krachten bijdragen aan de voortbewe-
ging houdt aktiviteit in de relevante spiergroepen op,
De afzet wordt grotendeels teweeggebracht door het dyna-
misch effect van de massa van het dier; 5) bij het paard,
de voorwaartse beweging van het achterbeen begint in het
laatste deel van de steunfase, bij de hond in het begin
van de zweeffase; 6) de verschillen in de periodes
waarin aktiviteit in de delen van de quadriceps optreedt
(aan het einde van de steunfase de M. vastus lateralis
bij het paard, de M. rectus femoris bij de hond) ver-
klaard kan worden door het slotmechanisme van de knie van
het paard: om vasthaken van de knieschijf op de mediale
rolkam van de trochlea femoris te voorkomen draait de
M. vastus lateralis de knieschijf naar lateraal; 7) bij
het paard gedurende de hele steunfase buiging optreedt
van de knie, terwijl in het tweede deel van de steunfase
de sprong wordt gestrekt; 8) de pezen van het spanzaag-
mechanisme gedurende de steunfase elastische energie
opslaan; deze energie wordt gebruikt voor de buiging
van de sprong; 9) de hond met zijn geheel uit spierweef-
sel bestaande teenbuigers de nagels in de grond kan
drukken ten behoeve van een geforceerde afzet; 10) aan
het einde van de steunfase bij het paard en niet bij de
hond aktiviteit optreedt in de M. tibialis cranialis;
dit verschil wordt verklaard doordat bij het paard de
pijp aan het einde van de steunfase de vertikale lijn
passeert, terwijl bij de hond de middenvoet ongeveer ver-
tikaal blijft; 11) de bewegingen van het achterbeen van
het paard theoretische uitgevoerd zouden kunnen worden
zonder aanwezigheid van de M. gastrocnemius en de M.
tibialis cranialis. Deze spieren centreren mogelijk de
werklijn van de belasting op het been door de lengteas
van de tibia. Deze veronderstelling kan alleen bewezen
worden door in vivo onderzoek met rekstrookjes.
101
-ocr page 104-
ll*u
CURRICULUM VITAE
De schrijver van dit proefschrift werd geboren op
6 januari 1945 te Zelhem. Na het behalen van het diploma
Gymnasium B aan het Gemeentelijk Lyceum te Enschede in 1963
werd een begin gemaakt met de studie Diergeneeskunde aan de
Rijksuniversiteit te Utrecht. Hij beëindigde deze studie
in 1969 en trad als wetenschappelijk medewerker in dienst
van de Kliniek voor Kleine Huisdieren. Sinds 1973 is de
schrijver van dit proefschrift verbonden aan het Instituut
voor Veterinaire Anatomie (Vakgroep Funktionele Morfologie)
van bovengenoemde Rijksuniversiteit.
102
Ck> TiZl
-ocr page 105-
STELLINGEN
I
De transektie van de mediale insertiepees van de M. tibialis
cranialis (spatpees) als therapie tegen spat moet twijfelachtig
genoemd worden: het resultaat van deze ingreep hangt af van de
ernst van de veranderingen aan kraakbeen en spongiosa van os
tarsi centrale en os tarsale tertium.
II
De diagnose "ruptuur van de peroneus tertius" dient te worden
gewijzigd in "ruptuur van de peroneus tertius en M. tibialis
cranialis".
III
Het feit dat bij het paard degeneratieve veranderingen het
meest worden gezien in het spronggewricht en bij de hond in
het kniegewricht wordt waarschijnlijk mede veroorzaakt door
verschil in gebruik van de spieren van het achterbeen bij
beide diersoorten.
IV
Bij het du'beltreden van de tenen van het achterbeen van de
hond dient te worden gedacht aan een beschadiging van zowel
de N. tibialis als de N. peroneus en niet van de N. peroneus
alleen.
V
De mate waarin bij het paard buiging van de knie optreedt in
de steunfase wordt mede bepaald door leeftijd en ras.
VI
De gelijktijdige aktiviteit in de M. tibialis cranialis en de
diepe buiger bij het paard rechtvaardigt de uitspraak,
dat de M. tibialis cranialis niet alleen als flexor kan
worden beschouwd.
-ocr page 106-
VII
De opvatting als zouden unguligrade dieren met viertenige
spreidvoeten minder ver in de grond zakken en dus beter zijn
aangepast aan het lopen op drassige grond dan ééntenige
unguligrade dieren, wordt door de feiten niet gesteund.
VIII
Het verschil in relief van de tibia bij Hipparion en Equus
wettigt het vermoeden dat een spanzaagmechanisme niet bij het
eerstgenoemde geslacht voorkwam.
IX
Het klinisch gerichte onderwijs van vakgroepen in de
Faculteit der Diergeneeskunde dient zodanig van inhoud en
opzet te zijn, dat het in principe door alle ervaren
dierenarts-docenten van die vakgroep kan worden gegeven.
X
Het ware wenselijk om voor een examen behalve een norm ook een
maximum aantal jaren vast te stellen.
XI
De prikklok registreert slechts lijfelijke, geen geestelijke
afwezigheid; voor velen onder de moderne vrijgestelden is
er dus niets te duchten.
XII
Wanneer het Nederlands voetbalelftal uit politici zou worden
geselekteerd, dan zou het Nederlandse volk uitsluitend
taktische besprekingen te zien krijgen.
Biomechanics of the hind limb
of horse and dog
G.H. Wentink
8 juni 1978