928 AJVR, Vol 62, No. 6, June 2001
Three-dimensional biomechanical analysis of the
hind limb requires knowledge of the magnitudes
and directions of all forces acting on the limb.1-13 These
forces include the joint reaction forces and moments
and the forces in all the muscles that surround the
joints of the limb. Forces transmitted by joints and
associated periarticular structures and muscle forces
are difficult to determine directly through in vivo mea-
surements.3-6,8,13 Therefore, an indirect approach is typ-
ically used to determine these forces and moments.
Such an approach is based on modeling the hind limb
as a system of rigid bodies connected at the joints.
Forces and moments acting on these bodies are then
determined by solving the equations governing their
equilibrium.
Formulating and solving these equations requires
some basic morphometric and anatomic data concern-
ing the physiologic cross-sectional area (PCSA),
architectural index (AI), and angle of pennation of
each muscle and the location of each muscle’s origin
and insertion. The PCSA of a muscle represents the
ratio of muscle volume to effective muscle fiber
length.14 It reflects the number of sarcomeres in paral-
lel in that muscle and is, therefore, proportional to the
amount of force the muscle can generate. The AI of a
muscle, on the other hand, reflects the number of sar-
comeres in series in that muscle and is, therefore, pro-
portional to the potential velocity of muscle contrac-
tion. Values for the PCSA of the muscles of the lower
limb in humans,6,14 the hind limb in cats,15 and the fore-
limb in chimpanzees16 have been published. To our
knowledge, however, information regarding the PCSA
of the muscles of the hind limb in dogs has not been.
Formulation of these equations of equilibrium also
requires knowledge of the direction of force in each
muscle and its moment arm around the joint on which
it has an effect. A common method of determining the
direction of force in a muscle is the straight line
model.5,7,9,17,18 This model assumes that the force gener-
ated by a muscle acts along the straight line that con-
nects the origin and insertion of that muscle. The
moment arm of a muscle about a joint is the vector
connecting the muscle’s point of insertion to the joint
center.1-5,7,9,10,13,18 Therefore, biomechanical analysis of
the hind limb requires information on the locations of
the origins and insertions of all muscles that affect the
joints of the hind limb, as well as the locations of all
joint centers.
The purpose of the study reported here was to
obtain the anatomic and morphometric data required
for biomechanical analysis of the hind limb in dogs.
This included determining the PCSA, AI, and angle of
pennation for all muscles of the hind limb, the coordi-
nates of the origins and insertions of those muscles,
and the coordinates of bony landmarks that would
allow determination of the locations of the centers of
the joints of the hind limb.
Materials and Methods
Morphometric variables—An adult mixed-breed 23-kg
male dog was used. The dog had been euthanatized at a local
pound because of dog population control regulations; it had
been healthy at the time of euthanasia. Immediately after the
dog was euthanatized, the skin and subcutaneous tissues of
the hindquarters were carefully removed. All muscles of the
right hind limb were identified and meticulously removed,
taking care to preserve all muscle tissue. Muscles that had
both their origin and insertion in the tibial-tarsal-metatarsal
unit were discarded, because the model used in this study
considered this unit to be rigidly connected, eliminating the
effect of these muscles. All tendinous tissue was discarded,
and muscles were weighed. The following muscles were eval-
uated: gluteus superficialis muscle, gluteus medius muscle,
gluteus profundus muscle, piriformis muscle, cranial portion
of the tensor fasciae latae muscle, caudal portion of the ten-
sor fasciae latae muscle, cranial portion of the sartorius mus-
cle, caudal portion of the sartorius muscle, rectus femoris
muscle, biceps femoris muscle, abductor cruris caudalis mus-
cle, semimembranosus muscle, semitendinosus muscle, gra-
cilis muscle, adductor longus muscle, adductor magnus et
brevis muscle, pectineus muscle, obturatorius internus mus-
cle, obturatorius externus muscle, gemelli muscle, quadratus
femoris muscle, articularis coxae muscle, iliopsoas muscle,
vastus lateralis muscle, vastus intermedius muscle, vastus
medialis muscle, popliteus muscle, extensor digitorum
longus muscle, medial head of the gastrocnemius muscle,
Received Apr 18, 2000.
Accepted Jun 26, 2000.
From the Section of Surgery, Koret School of Veterinary Medicine,
Hebrew University of Jerusalem, Jerusalem, Israel.
Morphometric and anatomic study
of the hind limb of a dog
Ron Shahar, DVM, and Joshua Milgram, DVM
Objective—To obtain the anatomic and morphomet-
ric data required for biomechanical analysis of the
hind limb in dogs.
Animals—A healthy adult mixed-breed 23-kg male
dog.
Procedure—Following euthanasia of the dog, all
muscles of the right hind limb were identified and
meticulously removed. Physiologic cross-sectional
areas (PCSA) and architectural indices (AI) were cal-
culated. The coordinates for the origin and insertion
of each muscle were determined, using orthogonal
right-handed coordinate systems embedded in the
pelvis, femur, and tibia.
Results—PCSA and AI were calculated for 29 mus-
cles, and coordinates for the origins and insertions of
these muscles were determined.
Conclusions—Results provide the morphometric
and anatomic data necessary for 3-dimensional bio-
mechanical studies of the hind limb in dogs. (
Am J
Vet Res
2001;62:928–933)
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