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LEG
14. 05. 2014
Kaan Yücel
M.D., Ph.D.
http://yeditepeanatomy1.org
Dr. Kaan Yücel
http://yeditepeanatomy1.org
Leg
The leg region (L. regio cruris) is the part that lies between the knee and and ankle joint. It includes most of
the tibia (shin bone) and fibula (calf bone). The leg (L., crus) connects the knee and foot. Often laypersons refer
incorrectly to the entire lower limb as “the leg.”
Two intermuscular septa pass from its deep aspect to be attached to the fibula. These, together with the
interosseous membrane, divide the leg into three compartments “anterior, lateral, and posterior”; each having its
own muscles, blood supply, and nerve supply.
Inferiorly, two band-like thickenings of the fascia form retinacula that bind the tendons of the anterior
compartment muscles before and after they cross the ankle joint, preventing them from bowstringing anteriorly
during dorsiflexion of the joint.
There are four muscles in the anterior compartment of the leg- tibialis anterior, extensor hallucis longus,
extensor digitorum longus, and fibularis tertius. These muscles pass and insert anterior to the transversely oriented
axis of the ankle (talocrural) joint and, therefore, are dorsiflexors of the ankle joint, elevating the forefoot and
depressing the heel [Collectively they dorsiflex the foot at the ankle joint, extend the toes, and invert the foot].
All the muscles of the anterior compartment of the leg are innervated by the deep fibular nerve, which is a
branch of the common fibular nerve.
The artery associated with the anterior compartment of leg is the anterior tibial artery, which passes forward
into the anterior compartment of leg. The smaller terminal branch of the popliteal artery, the anterior tibial artery,
begins at the inferior border of the popliteus muscle (i.e., as the popliteal artery passes deep to the tendinous arch of
the soleus). At the ankle joint, midway between the malleoli, the anterior tibial artery changes names, becoming the
dorsalis pedis artery (dorsal artery of the foot).
The nerve associated with the anterior compartment of the leg is the deep fibular (peroneal) nerve. It is one of
the two terminal branches of the common fibular nerve, arising between the fibularis longus muscle and the neck of
the fibula in the lateral compartment. A lesion of this nerve results in an inability to dorsiflex the ankle (footdrop).
There are two muscles in the lateral compartment of leg (evertor compartment)- fibularis longus and fibularis
brevis. Both evert the foot (turn the sole outward) and are innervated by the superficial fibular nerve, which is a
branch of the common fibular nerve. The lateral compartment is the smallest (narrowest) leg compartment.
Muscles in the posterior (plantarflexor) compartment of leg, the largest of the three leg compartments, are
organized into two groups, superficial and deep, by the transverse intermuscular septum. Generally, the muscles
mainly plantarflex and invert the foot and flex the toes. All are innervated by the tibial nerve.
Muscles of the posterior compartment produce plantarflexion at the ankle, inversion at the subtalar and
transverse tarsal joints, and flexion of the toes. Plantarflexion is a powerful movement (four times stronger than
dorsiflexion) produced over a relatively long range (approximately 50° from neutral) by muscles that pass posterior
to the transverse axis of the ankle joint.
The popliteal artery is the major blood supply to the leg and foot and enters the posterior compartment of leg
from the popliteal fossa behind the knee. The popliteal artery passes into the posterior compartment of leg between
the gastrocnemius and popliteus muscles. As it continues inferiorly it passes under the tendinous arch formed
between the fibular and tibial heads of the soleus muscle and enters the deep region of the posterior compartment of
leg where it immediately divides into an anterior tibial artery and a posterior tibial artery.
The nerve associated with the posterior compartment of leg is the tibial nerve, a major branch of the sciatic nerve
that descends into the posterior compartment from the popliteal fossa.
The tibial nerve leaves the posterior compartment of leg at the ankle by passing through the tarsal tunnel behind the
medial malleolus. It enters the foot to supply most intrinsic muscles and skin. In the leg, the tibial nerve gives rise
to:
• branches that supply all the muscles in the posterior compartment of leg
• two cutaneous branches, the sural nerve and medial calcaneal nerve.
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1. LEG
The leg region (L. regio cruris) is the part that lies between the knee and and ankle joint. It includes
most of the tibia (shin bone) and fibula (calf bone). The leg (L., crus) connects the knee and foot. Often
laypersons refer incorrectly to the entire lower limb as “the leg.”
 proximally, most major structures pass between the thigh and leg through or in relation to the popliteal
fossa behind the knee;
 distally, structures pass between the leg and foot mainly through the tarsal tunnel on the posteromedial side
of the ankle, the exceptions being the anterior tibial artery and the ends of the deep and superficial fibular
nerves, which enter the foot anterior to the ankle.
2. FASCIAL COMPARTMENTS OF THE LEG
The deep fascia of the leg is called the crural fascia. The deep fascia surrounds the leg and is continuous
above with the deep fascia of the thigh. Two intermuscular septa pass from its deep aspect to be attached to
the fibula. These, together with the interosseous membrane, divide the leg into three compartments “anterior,
lateral, and posterior”; each having its own muscles, blood supply, and nerve supply.
Inferiorly, two band-like thickenings of the fascia form retinacula that bind the tendons of the anterior
compartment muscles before and after they cross the ankle joint, preventing them from bowstringing
anteriorly during dorsiflexion of the joint:
 The superior extensor retinaculum is a strong, broad band of deep fascia, passing from the fibula to the
tibia, proximal to the malleoli.
 The inferior extensor retinaculum, a Y-shaped band of deep fascia, attaches laterally to the
anterosuperior surface of the calcaneus. It forms a strong loop around the tendons of the fibularis tertius and
the extensor digitorum longus muscles.
Flexor retinaculum; extends from the medial malleolus downward and backward to be attached to the medial
surface of the calcaneum. It binds the tendons of the deep muscles of the back of the leg to the back of the
medial malleolus as they pass forward to enter the sole. The tendons lie in compartments, each of which is
lined by a synovial sheath.
Superior peroneal retinaculum; connects the lateral malleolus to the lateral surface of the calcaneum. It
binds the tendons of the peroneus longus and brevis to the back of the lateral malleolus. The tendons are
provided with a common synovial sheath.
Inferior peroneal retinaculum; binds the tendons of the peroneus longus and brevis muscles to the lateral
side of the calcaneum. The tendons each possess a synovial sheath, which is continuous above with the
common sheath.
3. ANTERIOR COMPARTMENT OF THE LEG
The anterior compartment of the leg, or dorsiflexor (extensor) compartment, is located anterior to the
interosseous membrane, between the lateral surface of the shaft of the tibia and the medial surface of the shaft
of the fibula, and anterior to the intermuscular septum that connects them. The anterior compartment is
bounded anteriorly by the deep fascia of the leg and skin.
MUSCLES
[ See Table 1 for origins, insertions, innervations and main functions]
There are four muscles in the anterior compartment of the leg- tibialis anterior, extensor hallucis
longus, extensor digitorum longus, and fibularis tertius. These muscles pass and insert anterior to the
transversely oriented axis of the ankle (talocrural) joint and, therefore, are dorsiflexors of the ankle joint,
elevating the forefoot and depressing the heel [Collectively they dorsiflex the foot at the ankle joint, extend
the toes, and invert the foot]. All the muscles of the anterior compartment of the leg are innervated by the
deep fibular nerve, which is a branch of the common fibular nerve.
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Tibialis anterior
The tibialis anterior muscle is the most anterior and medial (and also the most superficial) of the
muscles in the anterior compartment of leg. The long tendon of the tibialis anterior begins halfway down the
leg and descends along the anterior surface of the tibia. Its tendon passes within its own synovial sheath deep
to the superior and inferior extensor retinacula to its attachment on the medial side of the foot. In so doing, its
tendon is located farthest from the axis of the ankle joint, giving it the most mechanical advantage and making
it the strongest dorsiflexor. Although antagonists at the ankle joint, the tibialis anterior and the tibialis
posterior (in the posterior compartment) both cross the subtalar and transverse tarsal joints to attach to the
medial border of the foot. Thus they act synergistically to invert the foot.
The tibialis anterior dorsiflexes the foot at the ankle joint and inverts the foot at the intertarsal joints.
During walking, it provides dynamic support for the medial arch of the foot.
Extensor hallucis longus
The extensor hallucis longus muscle is a thin muscle which lies between the tendons of the tibialis
anterior and extensor digitorum longus in the lower one-half of the leg and descends into the foot. The
extensor hallucis longus extends the great toe. As it crosses anterior to the ankle joint, it also dorsiflexes the
foot at the ankle joint.
Extensor digitorum longus
The extensor digitorum longus muscle is the most posterior and lateral of the muscles in the anterior
compartment of leg. The muscle becomes tendinous superior to the ankle, forming four tendons that attach to
the phalanges of the lateral four toes. A common synovial sheath surrounds the four tendons of the extensor
digitorum longus (plus that of the fibularis tertius) as they diverge on the dorsum of the foot and pass to their
distal attachments.
Fibularis tertius
The fibularis tertius muscle is a separated part of extensor digitorum longus, which shares its
synovial sheath. Proximally, the attachments and fleshy parts of the two muscles are continuous; however,
distally the fibularis tertius tendon is separate and attaches to the 5th metatarsal, not to a phalanx. Although
fibularis tertius contributes (weakly) to dorsiflexion, it also acts at the subtalar and transverse tarsal joints,
contributing to eversion of the foot. It may play a special proprioceptive role in sensing sudden inversion and
then contracting reflexively to protect the anterior tibiofibular ligament, the most commonly sprained
ligament of the body. The fibularis tertius is not always present.
Figures 1 & 2. Muscles of the anterior compartment of the leg
http://biology.clc.uc.edu/fankhauser/labs/anatomy_&_physiology/a&p201/muscles/muscles_legs/muscles_legs.htm
http://www.getbodysmart.com/ap/muscularsystem/footmuscles/menu/menu.html
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ARTERIES & VEINS
Anterior tibial artery
The artery associated with the anterior compartment of leg is the anterior tibial artery, which passes
forward into the anterior compartment of leg. The smaller terminal branch of the popliteal artery, the anterior
tibial artery, begins at the inferior border of the popliteus muscle (i.e., as the popliteal artery passes deep to the
tendinous arch of the soleus). The artery immediately passes anteriorly through a gap in the superior part of
the interosseous membrane to descend on the anterior surface of this membrane between the tbialis anterior
and extensor digitorum longus muscles. At the ankle joint, midway between the malleoli, the anterior tibial
artery changes names, becoming the dorsalis pedis artery (dorsal artery of the foot).
Distally, the anterior tibial artery gives rise to an anterior medial malleolar artery and an
anterior lateral malleolar artery, which pass posteriorly around the distal ends of the tibia and fibula,
respectively. These vessels connect with vessels from the posterior tibial and fibular arteries to form an
anastomotic network around the ankle. Deep veins follow the arteries and have similar names.
Figure 3. Anterior tibial artery & posterior tibial artery
http://www.gla.ac.uk/ibls/US/fab/tutorial/generic/sapulse.html
Table 1. Muscles of the anterior compartment of the leg.
Muscle
Origin
Insertion
Tibialis anterior
Extensor digitorum
longus
Extensor hallucis
longus
Fibularis tertius
Lateral condyle
Superior half of
lateral surface of
tibia and
interosseous
membrane
Lateral condyle of
tibia
Superior ¾ of
medial surface of
fibula and
interosseous
membrane
Middle part of
anterior surface of
fibula and
interosseous
membrane
Inferior third of
anterior surface of
fibula and
interosseous
membrane
Medial cuneiform
and base of 1st
metatarsal
Innervation
Main Action
Deep fibular nerve
(L4, L5)
Dorsiflexes ankle and
inverts foot
Middle and distal
phalanges of lateral
four digits
Extends lateral four
digits and dorsiflexes
ankle
Dorsal aspect of base
of distal phalanx of
great toe (hallux)
Extends great toe and
dorsiflexes ankle
Dorsum of base of
5th metatarsal
Dorsiflexes ankle and
aids in eversion of
foot
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NERVES
Deep fibular nerve
The nerve associated with the anterior compartment of the leg is the deep fibular (peroneal) nerve.
It is one of the two terminal branches of the common fibular nerve, arising between the fibularis
longus muscle and the neck of the fibula in the lateral compartment. The deep fibular nerve passes through the
intermuscular septum and then passes deep to the extensor digitorum longus. It reaches the anterior
interosseous membrane where it descends with the anterior tibial artery. The deep fibular nerve then exits
the anterior compartment, continuing across the ankle joint to supply intrinsic muscles (extensors digitorum
and hallucis brevis) and a small area of the skin of the foot. A lesion of this nerve results in an inability to
dorsiflex the ankle (footdrop).
The deep fibular nerve:
 innervates all muscles in the anterior compartment;
 [continues into the dorsal aspect of the foot] innervates the extensor digitorum brevis, first two dorsal
interossei muscles, and supplies the skin between the great and second toes.
3. LATERAL COMPARTMENT OF THE LEG
MUSCLES
[ See Table 2 for origins, insertions, innervations and main functions]
There are two muscles in the lateral compartment of leg (evertor compartment)- fibularis longus and
fibularis brevis. Both evert the foot (turn the sole outward) and are innervated by the superficial fibular
nerve, which is a branch of the common fibular nerve. The lateral compartment is the smallest (narrowest)
leg compartment. It is bounded by the lateral surface of the fibula, the anterior and posterior intermuscular
septa, and the deep fascia of the leg. The lateral compartment ends inferiorly at the superior fibular
retinaculum, which spans between the distal tip of the fibula and the calcaneus. Here the tendons of the two
muscles of the lateral compartment (fibularis longus and brevis) enter a common synovial sheath to
accommodate their passage between the superior fibular retinaculum and the lateral malleolus, using the latter
as a trochlea as they cross the ankle joint.
The fibularis longus and fibularis brevis muscles have their fleshy bellies in the lateral compartment
but are tendinous as they exit the compartment within the common synovial sheath deep to the superior fibular
retinaculum. Both muscles are evertors of the foot, elevating the lateral margin of the foot.
Fibularis longus
The fibularis longus muscle arises in the lateral compartment of leg, but its tendon crosses under the
foot to attach to bones on the medial side. The common fibular nerve passes anteriorly around the fibular
neck between the attachments of the fibularis longus to the fibular head and shaft. Distal to the superior
fibular retinaculum, the common sheath shared by the fibular muscles splits to extend through separate
compartments deep to the inferior fibular retinaculum.
The fibularis longus everts and plantarflexes the foot. In addition, the fibularis longus, tibialis anterior,
and tibialis posterior muscles, which all insert on the undersurfaces of bones on the medial side of the foot,
together act as a stirrup to support the arches of the foot. The fibularis longus supports mainly the lateral and
transverse arches. When a person stands on one foot, the fibularis longus helps steady the leg on the foot.
Fibularis brevis
The fibularis brevis is a fusiform muscle that lies deep to the fibularis longus, and, true to its name, it
is shorter than its partner in the lateral compartment. Its broad tendon grooves the posterior aspect of the
lateral malleolus and can be palpated inferior to it. The narrower tendon of the fibularis longus lies on that of
the fibularis brevis and does not contact the lateral malleolus.
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Table 2. Muscles of the lateral compartment of the leg.
Muscle
Fibularis longus
Fibularis brevis
Proximal Attachment Distal Attachment
Innervation
Main Action
(Origin)
(Insertion)
Head and superior
Base of 1st
Superficial fibular
Everts foot and
2/3 of lateral surface
metatarsal and
nerve (L5, S1, S2)
weakly plantarflexes
of fibula
medial cuneiform
Inferior 2/3 of lateral
Dorsal surface of
surface of fibula
tuberosity on lateral
ankle
side of base of 5th
metatarsal
Figure 4. Peroneus (fibularis) longus & brevis muscles
http://quizlet.com/2514463/lower-appendicaular-musculature-flash-cards
ARTERIES & VEINS
No major artery passes vertically through the lateral compartment of leg. Instead, perforating branches and
accompanying veins supply blood to and drain blood from the compartment. Proximally, perforating branches
of the anterior tibial artery penetrate the anterior intermuscular septum. Inferiorly, perforating branches of the
fibular artery penetrate the posterior intermuscular septum, along with their accompanying veins (L. venae
comitantes). Deep veins generally follow the arteries.
NERVES
Superficial fibular nerve
The nerve associated with the lateral compartment of leg is the superficial fibular (peroneal) nerve.
This nerve originates as one of the two major branches of the common fibular nerve, which enters the lateral
compartment of leg from the popliteal fossa. After supplying the fibularis longus and fibularis brevis, the
superficial fibular nerve continues as a cutaneous nerve, supplying the skin on the distal part of the anterior
surface of the leg and nearly all the dorsum of the foot.
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Figure 5. Nerves in the lateral compartment of the leg
http://upload.wikimedia.org/wikipedia/commons/4/43/Gray835.png
The common fibular nerve originates from the sciatic nerve in the
posterior compartment of thigh or in the popliteal fossa, and follows the
medial margin of the biceps femoris tendon over the lateral head of the
gastrocnemius muscle and toward the fibula. Here it gives origin to two
cutaneous branches, which descend in the leg:
 Sural communicating nerve, which joins the sural branch of the
tibial nerve and contributes to innervation of skin over the lower
posterolateral side of the leg;
 Lateral sural cutaneous nerve, which innervates skin over the upper
lateral leg.
The common fibular nerve continues around the neck of the
fibula and enters the lateral compartment by passing between the
attachments of the fibularis longus muscle to the head and shaft of fibula.
Here the common fibular nerve divides into its two terminal branches:
 Superficial fibular nerve
 Deep fibular nerve
The superficial fibular nerve descends in the lateral
compartment deep to the fibularis longus and innervates the fibularis
longus and fibularis brevis. It then penetrates deep fascia in the lower leg
and enters the foot where it divides into medial and lateral branches,
which supply dorsal areas of the foot and toes except for:
the web space between the great and second toes, which is supplied by
the deep fibular nerve; the lateral side of the little toe, which is supplied
by the sural branch of the tibial nerve.
The deep fibular nerve passes anteromedially through the
intermuscular septum into the anterior compartment of leg, which it
supplies.
4. POSTERIOR COMPARTMENT OF THE LEG
MUSCLES
Muscles in the posterior (plantarflexor) compartment of leg, the largest of the three leg compartments,
are organized into two groups, superficial and deep, by the transverse intermuscular septum. Generally, the
muscles mainly plantarflex and invert the foot and flex the toes. All are innervated by the tibial nerve.
Muscles of the posterior compartment produce plantarflexion at the ankle, inversion at the subtalar and
transverse tarsal joints, and flexion of the toes. Plantarflexion is a powerful movement (four times stronger
than dorsiflexion) produced over a relatively long range (approximately 50° from neutral) by muscles that
pass posterior to the transverse axis of the ankle joint. Plantarflexion develops thrust, applied primarily at the
ball of the foot, that is used to propel the body forward and upward and is the major component of the forces
generated during the push-off (heel off and toe off) parts of the stance phase of walking and running.
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Superficial group
[ See Table 3 for origins, insertions, innervations and main functions]
The superficial group of calf muscles (muscles forming prominence of “calf” of posterior leg)
includes the gastrocnemius, soleus, and plantaris. All of these muscles insert onto the heel (calcaneus) of
the foot and plantarflex the foot at the ankle joint.
The gastrocnemius and soleus share a common tendon, the calcaneal tendon, which attaches to the
calcaneus. Collectively these two muscles make up the three-headed triceps surae (L. sura, calf). This
powerful muscular mass pulls on the lever provided by the calcaneal tuberosity, elevating the heel and
depressing the forefoot, generating as much as 93% of the plantarflexion force. As a unit, these muscles are
large and powerful because they take the body forward off the planted foot during walking and can elevate the
body upward onto the toes when standing. Two of the muscles (gastrocnemius and plantaris) originate on the
distal end of the femur and can also flex the knee.
A subcutaneous calcaneal bursa, located between the skin and the calcaneal tendon, allows the skin
to move over the taut tendon. A deep bursa of the calcaneal tendon (retrocal-caneal bursa), located between
the tendon and the calcaneus, allows the tendon to glide over the bone.
Gastrocnemius
The gastrocnemius muscle is the most superficial of the muscles in the posterior compartment and is
one of the largest muscles in the leg. It originates from two heads, one lateral and one media.
At the knee, the facing margins of the two heads of the gastrocnemius form the lateral and medial
borders of the lower end of the popliteal fossa. In the upper leg, the heads of the gastrocnemius combine to
form a single elongate muscle belly, which forms much of the soft tissue bulge identified as the calf. In the
lower leg, the muscle fibers of the gastrocnemius converge with those of the deeper soleus muscle to form the
calcaneal tendon, which attaches to the calcaneus (heel) of the foot. The gastrocnemius plantarflexes the
foot at the ankle joint and can also flex the leg at the knee joint.
The large size of the gastrocnemius and soleus muscles is a human characteristic that is directly related
to our upright stance. These muscles are strong and heavy because they lift, propel, and accelerate the weight
of the body when walking, running, jumping, or standing on the toes.
The calcaneal tendon (L. tendo calcaneus, Achilles tendon) is the most powerful (thickest and
strongest) tendon in the body. Approximately 15 cm in length, it is a continuation of the flat aponeurosis
formed halfway down the calf where the bellies of the gastrocnemius terminate.
Plantaris
The plantaris has a small muscle belly proximally and a long thin tendon, which descends through the
leg and joins the calcaneal tendon. This vestigial muscle is absent in 5-10% of people and is highly variable
in size and form when present. It acts with the gastrocnemius but is insignificant as either a flexor of the knee
or a plantarflexor of the ankle. The plantaris has been considered to be an organ of proprioception for the
larger plantarflexors. The short spindle-shaped muscle body of the plantaris descends medially between the
gastrocnemius and soleus muscles and eventually fuses with the medial side of the calcaneal tendon near its
attachment to the calcaneus. The plantaris contributes to plantarflexion of the foot at the ankle joint and
flexion of the leg at the knee joint, and is innervated by the tibial nerve.
Soleus
The soleus is a large flat muscle under the gastrocnemius muscle. In the lower leg, the soleus muscle
narrows to join the calcaneal tendon that attaches to the calcaneus. Electromyography (EMG) studies show
that during symmetrical standing, the soleus is continuously active.
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Figure 6. Calf muscles
http://www.floota.com/muscles_of_the_calf.html
Deep group
[See Table 4 for origins, insertions, innervations and main functions]
Four muscles make up the deep group in the posterior compartment of the leg: popliteus, flexor
digitorum longus, flexor hallucis longus, and tibialis posterior. The popliteus acts on the knee joint,
whereas the other muscles plantarflex the ankle with two continuing on to flex the toes. When the calcaneal
tendon is ruptured, these muscles cannot generate the power necessary to lift the body's weight (i.e., to stand
on the toes).
Popliteus
The popliteus is the smallest and most superior of the deep muscles in the posterior compartment of
the leg. It is a thin, triangular muscle that forms the inferior part of the floor of the popliteal fossa. It unlocks
the extended knee at the initiation of flexion and stabilizes the knee. The popliteus muscle ascends laterally
across the lower aspect of the knee. When initiating gait from a standing position, contraction of the popliteus
laterally rotates the femur on the fixed tibia, unlocking the knee joint.
Flexor hallucis longus
The flexor hallucis longus muscle is a powerful flexor of all of the joints of the great toe. The tendon
of the flexor hallucis longus slips into a distinct groove on the posterior surface of the adjacent tarsal bone
(talus) of the foot. The flexor hallucis longus flexes the great toe. It is particularly active during the toe-off
phase of walking when the body is propelled forward off the stance leg and the great toe is the last part of the
foot to leave the ground. It can also contribute to plantarflexion of the foot at the ankle joint.
Table 3. Muscles of the superficial compartment of the leg.
Muscle
Gastrocnemius
Origin
Lateral head: lateral aspect of lateral
Insertion
Posterior
Innervation
Tibial nerve
Main Action
Plantarflexes
condyle of femur
surface of
(S1, S2)
ankle when knee
Medial head: popliteal surface of
calcaneus via
is extended;
femur; superior to medial condyle
calcaneal
raises heel during
tendon
walking; flexes
leg at knee joint
Soleus
Posterior aspect of head and superior
Plantarflexes
quarter of posterior surface of fibula;
ankle
soleal line and middle third of medial
independent of
border of tibia; and tendinous arch
position of knee;
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extending between the bony
steadies leg on
attachments
foot
Inferior end of lateral supracondylar line
Weakly assists
of femur; oblique popliteal ligament
gastrocnemius in
plantarflexing
ankle
Flexor digitorum longus
The flexor digitorum longus muscle originates on the medial side of the posterior compartment of
leg. The tendon crosses inferior to the tendon of the flexor hallucis longus muscle to reach the medial side of
the foot and then divides into four tendons. The flexor digitorum longus flexes the lateral four toes. It is
involved with gripping the ground during walking and propelling the body forward off the toes at the end of
the stance phase of gait. The two muscles of the posterior compartment that pass to the toes are crisscrossed.
The muscle attaching to the great toe (flexor hallucis longus) arises laterally (from the fibula) in the deep
subcompartment, and the muscle attaching to the lateral four toes (flexor digitorum longus) arises medially
(from the tibia). Their tendons cross in the sole of the foot.
Tibialis posterior
The tibialis posterior muscle lies between and is overlapped by the flexor digitorum longus and the
flexor hallucis longus muscles. Near the ankle, the tendon of the tibialis posterior is crossed superficially by
the tendon of the flexor digitorum longus muscle and lies medial to this tendon in the groove on the posterior
surface of the medial malleolus. The tibialis posterior inverts and plantarflexes the foot, and supports the
medial arch of the foot during walking.
Table 4. Muscles of the deep compartment of the leg.
Muscle
Popliteus
Origin
Insertion
Innervation
Main Action
Lateral surface of
Posterior surface of tibia,
Tibial nerve
Weakly flexes knee
lateral condyle of
superior to soleal line
(L4, L5, S1)
and unlocks it by
femur and lateral
rotating femur 5° on
meniscus
fixed tibia; medially
rotates tibia of
unplanted limb
Flexor hallucis
Inferior 2/3 of
Base of distal phalanx of great
Flexes great toe at all
longus
posterior surface of
toe (hallux)
joints; weakly
fibula; inferior part of
plantarflexes ankle;
interosseous
supports medial
membrane
longitudinal arch of
foot
Flexor digitorum
Medial part of
Bases of distal phalanges of
Flexes lateral four
longus
posterior surface of
lateral four digits
digits; plantarflexes
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Dr. Kaan Yücel
Tibialis posterior
http://yeditepeanatomy1.org
Leg
tibia inferior to soleal
ankle; supports
line; by a broad tendon
longitudinal arches
to fibula
of foot
Interosseous
Tuberosity of navicular,
Plantarflexes ankle;
membrane; posterior
cuneiform, cuboid, and
inverts foot
surface of tibia inferior
sustentaculum tali of
to soleal line; posterior
calcaneus; bases of 2nd, 3rd,
surface of fibula
and 4th metatarsals
ARTERIES
POPLITEAL ARTERY
The popliteal artery is the major blood supply to the leg and foot and enters the posterior
compartment of leg from the popliteal fossa behind the knee. The popliteal artery passes into the posterior
compartment of leg between the gastrocnemius and popliteus muscles. As it continues inferiorly it passes
under the tendinous arch formed between the fibular and tibial heads of the soleus muscle and enters the deep
region of the posterior compartment of leg where it immediately divides into an anterior tibial artery and a
posterior tibial artery.
ANTERIOR TIBIAL ARTERY
The anterior tibial artery passes forward through the aperture in the upper part of the interosseous
membrane and enters the anterior compartment of leg. It continues inferiorly onto the dorsal aspect of the
foot.
POSTERIOR TIBIAL ARTERY
The posterior tibial artery descends through the deep region of the posterior compartment of leg on
the superficial surfaces of the tibialis posterior and flexor digitorum longus muscles. It passes through the
tarsal tunnel behind the medial malleolus and continues into the sole of the foot. In the leg, the posterior tibial
artery has two major branches, the circumflex fibular artery and fibular artery:
 Circumflex fibular artery passes laterally through the soleus muscle and around the neck of the fibula to
connect with the anastomotic network of vessels surrounding the knee;
 Fibular artery is the largest and most important branch. It arises inferior to the distal border of the
popliteus and the tendinous arch of the soleus. It parallels the course of the posterior tibial artery, but descends
along the lateral side of the posterior compartment. The fibular artery passes behind the attachment between
the distal ends of the tibia and fibula and terminates in a network of vessels over the lateral surface of the
calcaneus.
 The nutrient artery of tibia, the largest nutrient artery in the body, arises from the origin of the anterior or
posterior tibial artery.
Deep veins in the posterior compartment generally follow the arteries.
12
Dr. Kaan Yücel
http://yeditepeanatomy1.org
Leg
NERVES
Figure 7. Tibial nerve
http://en.wikipedia.org/wiki/File:Gray832.png
.
Tibial nerve
The nerve associated with the posterior compartment of leg is the
tibial nerve, a major branch of the sciatic nerve that descends into the
posterior compartment from the popliteal fossa.
The tibial nerve passes under the tendinous arch formed between
the fibular and tibial heads of the soleus muscle and passes vertically
through the deep region of the posterior compartment of leg on the
surface of the tibialis posterior muscle with the posterior tibial vessels.
The tibial nerve leaves the posterior compartment of leg at the ankle by
passing through the tarsal tunnel behind the medial malleolus. It enters the
foot to supply most intrinsic muscles and skin.
In the leg, the tibial nerve gives rise to:
• branches that supply all the muscles in the posterior compartment of leg
• two cutaneous branches, the sural nerve and medial calcaneal nerve.
Sural nerve
The sural nerve originates high in the leg between the two heads of the
gastrocnemius muscle. It descends superficial to the belly of the
gastrocnemius muscle and penetrates through the deep fascia
approximately in the middle of the leg where it is joined by a sural
communicating branch from the common fibular nerve. It passes down
the leg, around the lateral malleolus, and into the foot.
The sural nerve supplies skin on the lower posterolateral surface of the leg
and the lateral side of the foot and little toe.
Medial calcaneal nerve
The medial calcaneal nerve is often multiple and originates from the
tibial nerve low in the leg near the ankle and descends onto the medial
side of the heel. The medial calcaneal nerve innervates skin on the medial
surface and sole of the heel.
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