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LEG
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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.
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.
ANTERO-LATERAL ASPECT OF THE LEG
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].
Dorsiflexion is actively used in the swing phase of walking, when concentric contraction keeps the
forefoot elevated to clear the ground as the free limb swings forward. Immediately after, in the stance phase,
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eccentric contraction of the tibialis anterior controls the lowering of the forefoot to the floor following heel
strike. During standing, the dorsiflexors reflexively pull the leg (and thus the center of gravity) anteriorly on the
fixed foot when the body starts to lean (the center of gravity begins to shift too far) posteriorly.
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.
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.
To test the the tibialis anterior, the person is asked to stand on the heels or dorsiflex the foot against
resistance; if normal, its tendon can be seen and palpated.
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. Because it crosses anterior to the ankle joint, it also dorsiflexes the foot at
the ankle joint. To test the extensor hallucis longus, the great toe is dorsiflexed against resistance; if acting
normally, its entire tendon can be seen and palpated.
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. To test the extensor digitorum longus, the lateral four toes are dorsiflexed against
resistance; if acting normally, the tendons can be seen and palpated. The extensor digitorum longus extends the
toes and dorsiflexes the foot at the ankle joint.
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
FT 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.
Arteries
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 through an aperture in the interosseous membrane.
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).
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Table 1. Muscles of the anterior compartment of the leg.
Muscle
Tibialis anterior
Extensor digitorum
longus
Extensor hallucis
longus
Fibularis tertius
Origin
Lateral condyle and
superior half of
lateral surface of tibia
and interosseous
membrane
Lateral condyle of
tibia and superior
three quarters 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
Insertion
Medial cuneiform
and base of 1st
metatarsal
Innervation
Deep fibular nerve
(L4, L5)
Main Action
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
http://biology.clc.uc.edu/fankhauser/labs/anatomy_&_physiology/a&p201/muscles/muscles_legs/muscles_legs.htm
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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.
Veins
Deep veins follow the arteries and have similar names.
Nerves
Deep fibular nerve
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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
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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.
Lateral compartment of 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. As evertors, the
fibularis muscles act at the subtalar and transverse tarsal joints. From the neutral position, only a few degrees of
eversion are possible. In practice, the primary function of the evertors of the foot is not to elevate the lateral
margin of the foot (the common description of eversion) but to depress or fix the medial margin of the foot in
support of the toe off phase of walking and, especially, running and to resist inadvertent or excessive inversion
of the foot (the position in which the ankle is most vulnerable to injury). When standing (and particularly when
balancing on one foot), the fibularis muscles contract to resist medial sway (to recenter a line of gravity, which
has shifted medially) by pulling laterally on the leg while depressing the medial margin of the foot.
To test the fibularis longus and brevis, the foot is everted strongly against resistance; if acting normally,
the muscle tendons can be seen and palpated inferior to the lateral malleolus.
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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
Table 2. Muscles of the lateral compartment of the leg.
Muscle
Fibularis longus
Fibularis brevis
Proximal Attachment
(Origin)
Head and superior
two thirds of lateral
surface of fibula
Inferior two thirds of
lateral surface of
fibula
Distal Attachment
(Insertion)
Base of 1st
metatarsal and
medial cuneiform
Dorsal surface of
tuberosity on lateral
side of base of 5th
metatarsal
Innervation
Main Action
Superficial fibular
nerve (L5, S1, S2)
Everts foot and
weakly plantarflexes
ankle
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Arteries
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).
Veins
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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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
http://upload.wikimedia.org/wikipedia/commons/4/43/Gray835.png
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.
Posterior aspect 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.
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 tugs on the lever provided by the calcaneal tuberosity,
elevating the heel and thus depressing the forefoot, generating as much as 93% of the plantarflexion force.
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As a unit, these muscles are large and powerful because they propel 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.
To test the triceps surae, the foot is plantarflexed against resistance (e.g., by “standing on the toes,” in
which case body weight [gravity] provides resistance). If normal, the calcaneal tendon and triceps surae can be
seen and palpated.
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.
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 by resisting lateral (external) rotation of the
tibia on the femur. 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
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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. To test the flexor
hallucis longus, the distal phalanx of the great toe is flexed against resistance; if normal, the tendon can be seen
and palpated on the plantar aspect of the great toe as it crosses the joints of the toe.
Table 3. Muscles of the superficial compartment of the leg.
Muscle
Gastrocnemius
Origin
Lateral head: lateral aspect of
lateral condyle of femur
Medial head: popliteal surface of
femur; superior to medial condyle
Soleus
Plantaris
Insertion
Posterior
surface of
calcaneus via
calcaneal
tendon
Innervation
Tibial nerve
(S1, S2)
Posterior aspect of head and
superior quarter of posterior
surface of fibula; soleal line and
middle third of medial border of
tibia; and tendinous arch extending
between the bony attachments
Inferior end of lateral
supracondylar line of femur;
oblique popliteal ligament
Main Action
Plantarflexes ankle
when knee is
extended; raises heel
during walking; flexes
leg at knee joint
Plantarflexes ankle
independent of
position of knee;
steadies leg on foot
Weakly assists
gastrocnemius in
plantarflexing ankle
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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. To test the flexor digitorum longus, the distal phalanges of the lateral four toes are flexed
against resistance; if they are acting normally, the tendons of the toes can be seen and palpated.
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
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surface of the medial malleolus. The tibialis posterior inverts and plantarflexes the foot, and supports the medial
arch of the foot during walking. To test the tibialis anterior, the foot is inverted against resistance with the foot
in slight plantarflexion; if normal, the tendon can be seen and palpated posterior to the medial malleolus.
Table 4. Muscles of the deep compartment of the leg.
Muscle
Popliteus
Origin
Lateral surface of
lateral condyle of
femur and lateral
meniscus
Insertion
Posterior surface of
tibia, superior to
soleal line
Flexor hallucis longus
Inferior two thirds of
posterior surface of
fibula; inferior part of
interosseous
membrane
Base of distal phalanx
of great toe (hallux)
Flexor digitorum
longus
Medial part of
posterior surface of
tibia inferior to soleal
line; by a broad
tendon to fibula
Interosseous
membrane; posterior
surface of tibia
inferior to soleal line;
posterior surface of
fibula
Bases of distal
phalanges of lateral
four digits
Tibialis posterior
Innervation
Tibial nerve (L4, L5,
S1)
Tuberosity of
navicular, cuneiform,
cuboid, and
sustentaculum tali of
calcaneus; bases of
2nd, 3rd, and 4th
metatarsals
Main Action
Weakly flexes knee
and unlocks it by
rotating femur 5° on
fixed tibia; medially
rotates tibia of
unplanted limb
Flexes great toe at all
joints; weakly
plantarflexes ankle;
supports medial
longitudinal arch of
foot
Flexes lateral four
digits; plantarflexes
ankle; supports
longitudinal arches of
foot
Plantarflexes ankle;
inverts foot
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 of the tibial artery, arises inferior to the distal border
of the popliteus and the tendinous arch of the soleus. It parallels the course of the tibial artery, but descends
along the lateral side of the posterior compartment. The fibular artery passes behind the attachment between the
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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.
Veins
Deep veins in the posterior compartment generally follow the arteries.
Nerves
.
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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Lymphatic Drainage of the Leg
The greater part of the lymph from the skin and superficial fascia on the front of the leg drains upward
and medially in vessels that follow the great saphenous vein, to end in the vertical group of superficial inguinal
lymph nodes. Lymph vessels from the skin and superficial fascia on the back of the leg drain upward and either
pass forward around the medial side of the leg to end in the vertical group of superficial inguinal nodes or drain
into the popliteal nodes.
Gastrocnemius Strain
Gastrocnemius strain (tennis leg) is a painful acute injury resulting from partial tearing of the medial belly of
the gastrocnemius at or near its musculotendinous junction, often seen in individuals older than 40 years of age.
It is caused by overstretching the muscle by concomitant full extension of the knee and dorsiflexion of the ankle
joint. Usually, an abrupt onset of stabbing pain is followed by edema and spasm of the gastrocnemius.
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Calcaneal Tendon Reflex
The ankle jerk reflex, or triceps surae reflex, is a calcaneal tendon reflex. It is a myotatic reflex elicited while
the person's legs are dangling over the side of the examining table. The calcaneal tendon is struck briskly with a
reflex hammer just proximal to the calcaneus. The normal result is plantarflexion of the ankle joint. The
calcaneal tendon reflex tests the S1 and S2 nerve roots. If the S1 nerve root is injured or compressed, the ankle
reflex is virtually absent.
Ruptured Calcaneal Tendon
Rupture of the calcaneal tendon is often sustained by poorly conditioned people with a history of calcaneal
tendinitis. The injury is typically experienced as an audible snap during a forceful push off (plantarflexion with
the knee extended) followed immediately by sudden calf pain and sudden dorsiflexion of the plantarflexed foot.
In a completely ruptured tendon, a gap is palpable, usually 1-5 cm proximal to the calcaneal attachment. The
muscles affected are the gastrocnemius, soleus, and plantaris.
Calcaneal tendon rupture is probably the most severe acute muscular problem of the leg. Individuals with this
injury cannot plantarflex against resistance (cannot raise the heel from the ground or balance on the affected
side), and passive dorsiflexion (usually limited to 20° from neutral) is excessive.
Ambulation is possible only when the limb is laterally (externally) rotated, rolling over the transversely placed
foot during the stance phase without push off. Bruising appears in the malleolar region, and a lump usually
appears in the calf owing to shortening of the triceps surae. In older or nonathletic people, non-surgical repairs
are often adequate, but surgical intervention is usually advised for those with active lifestyles.
Calcaneal Tendinitis
Inflammation of the calcaneal tendon constitutes 9-18% of running injuries. Microscopic tears of collagen
fibers in the tendon, particularly just superior to its attachment to the calcaneus, result in tendinitis, which
causes pain during walking, especially when wearing rigidsoled shoes. Calcaneal tendinitis often occurs during
repetitive activities, especially in individuals who take up running after prolonged inactivity or suddenly
increase the intensity of their training, but it may also result from poor footwear or training surfaces.
Fabella in Gastrocnemius
Close to its proximal attachment, the lateral head of the gastrocnemius contains a sesamoid bone, the fabella
(L., bean), which articulates with the lateral femoral condyle and is visible in lateral radiographs of the knee in
3-5% of people..
Superficial Fibular Nerve Entrapment
Chronic ankle sprains may produce recurrent stretching of the superficial fibular nerve, which may cause pain
along the lateral side of the leg and the dorsum of the ankle and foot. Numbness and paresthesia (tickling or
tingling) may be present and increase with activity.
Deep Fibular Nerve Entrapment
Excessive use of muscles supplied by the deep fibular nerve (e.g., during skiing, running, and dancing) may
result in muscle injury and edema in the anterior compartment. This entrapment may cause compression of the
deep fibular nerve and pain in the anterior compartment.
Pain occurs in the dorsum of the foot and usually radiates to the web space between the 1st and 2nd toes.
Because ski boots are a common cause of this type of nerve entrapment, this condition has been called the “ski
boot syndrome”; however, the syndrome also occurs in soccer players and runners and can also result from tight
shoes.
Injury to Common Fibular Nerve and Footdrop
Because of its superficial position, the common fibular is the nerve most often injured in the lower limb, mainly
because it winds subcutaneously around the fibular neck, leaving it vulnerable to direct trauma. This nerve may
also be severed during fracture of the fibular neck or severely stretched when the knee joint is injured or
dislocated.
Severance of the common fibular nerve results in flaccid paralysis of all muscles in the anterior and lateral
compartments of the leg (dorsiflexors of ankle and evertors of foot). The loss of dorsiflexion of the ankle causes
footdrop, which is further exacerbated by unopposed inversion of the foot. This has the effect of making the
limb “too long”: The toes do not clear the ground during the swing phase of walking.
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There are several other conditions that may result in a lower limb that is “too long” functionally, for example,
pelvic tilt and spastic paralysis or contraction of the soleus. There are at least three means of compensating for
this problem:

A waddling gait, in which the individual leans to the side opposite the long limb, “hiking” the hip.

A swing-out gait, in which the long limb is swung out laterally (abducted) to allow the toes to clear the
ground.

A high-stepping steppage gait, in which extra flexion is employed at the hip and knee to raise the foot as
high as necessary to keep the toes from hitting the ground.
Because the dropped foot makes it difficult to make the heel strike the ground first as in a normal gait, a
steppage gait is commonly employed in the case of flaccid paralysis. Sometimes an extra “kick” is added as the
free limb swings forward in an attempt to flip the forefoot upward just before setting the foot down.
Injury to Tibial Nerve
Injury to the tibial nerve is uncommon because of its deep and protected position in the popliteal fossa;
however, the nerve may be injured by deep lacerations in the fossa. Posterior dislocation of the knee joint may
also damage the tibial nerve.
Complete division results in the following clinical
features:
Motor: All the muscles in the back of the leg and the sole of the foot are paralyzed. The opposing muscles
dorsiflex the foot at the ankle joint and evert the foot at the subtalar and transverse tarsal joints, an attitude
referred to as calcaneovalgus.
Sensory: Sensation is lost on the sole of the foot; later, trophic ulcers develop.
Posterior Tibial Pulse
The posterior tibial pulse can usually be palpated between the posterior surface of the medial malleolus and the
medial border of the calcaneal tendon. Because the posterior tibial artery passes deep to the flexor retinaculum,
it is important when palpating this pulse to have the person invert the foot to relax the retinaculum. Failure to
do so may lead to the erroneous conclusion that the pulse is absent.
Both arteries are examined simultaneously for equality of force. Palpation of the posterior tibial pulses is
essential for examining patients with occlusive peripheral arterial disease. Although posterior tibial pulses are
absent in approximately 15% of normal young people, absence of posterior tibial pulses is a sign of occlusive
peripheral arterial disease in people older than 60 years. For example, intermittent claudication, characterized
by leg pain and cramps, develops during walking and disappears after rest. These conditions result from
ischemia of the leg muscles caused by narrowing or occlusion of the leg arteries.
Superficial Peroneal Nerve Block
Area of anesthesia: Skin on the lower anterior and lateral sides of the leg and the dorsum of the foot and toes
(except the cleft between the first and second toes, which is innervated by the deep peroneal nerve and the
lateral side of the little toe, which is supplied by the sural nerve) Indications: Repair of lacerations in the area of
its cutaneous distribution.
Procedure: The superficial peroneal nerve is a branch of the common peroneal nerve. In the lower third of the
leg it becomes superficial and its terminal branches pass to their distribution on the dorsum of the foot and toes.
The superficial peroneal nerve is easily blocked in the lower part of the leg by infiltrating the anesthetic
in the subcutaneous tissue along a transverse line connecting the medial and lateral malleoli.
Deep Peroneal Nerve Block
Area of anesthesia: Skin in the cleft between the big and second toes
Indications: Repair of lacerations in the cleft between the big and second toes
Procedure: The deep peroneal nerve is a terminal branch of the common peroneal nerve. It descends in the
anterior compartment of the leg and at the ankle it passes onto the dorsum of the foot. Here the nerve lies on the
lateral side of the dorsalis pedis artery and is superficially placed between the tendons of extensor digitorum
longus and the extensor hallucis longus muscles.
First, the dorsalis pedis artery is palpated midway between the medial and lateral malleoli. With the foot
actively dorsiflexed, the tendons of the extensor digitorum longus and extensor hallucis longus muscles can be
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seen. The nerve lies on the lateral side of the artery between these tendons. The needle is then inserted over the
nerve, and the surrounding tissues are infiltrated with anesthetic.
Tibial Nerve Block
Area of anesthesia: Skin of the sole of the foot (medial and lateral plantar nerves)
Indications: Repair of lacerations on the sole of foot
Procedure: The tibial nerve (L4 and L5 and S1 through S3) is the largest terminal branch of the sciatic nerve.
At the ankle, the nerve, accompanied by the posterior tibial artery, becomes superficial. It lies behind the
medial malleolus, between the tendons of the flexor digitorum longus and the flexor hallucis longus muscles,
and is covered by the flexor retinaculum.
The tibial nerve may be blocked as it lies behind the medial malleolus. By careful palpation, the pulsations of
the posterior tibial artery can be felt midway between the medial malleolus and the heel. The nerve lies
immediately posterior to the artery, and the anesthetic needle can be inserted at this location.
Varicose Veins
A varicosed vein is one that has a larger diameter than normal and is elongated and tortuous. Varicosity
of the esophageal and rectal veins is described elsewhere. This condition commonly occurs in the superficial
veins of the lower limb and, although not life threatening, is responsible for considerable discomfort and pain.
Varicose veins have many causes, including hereditary weakness of the vein walls and incompetent
valves; elevated intraabdominal pressure as a result of multiple pregnancies or abdominal tumors; and
thrombophlebitis of the deep veins, which results in the superficial veins becoming the main venous pathway
for the lower limb. It is easy to understand how this condition can be produced by incompetence of a valve in a
perforating vein. Every time the patient exercises, high-pressure venous blood escapes from the deep
veins into the superficial veins and produces a varicosity, which might be localized to begin with but becomes
more extensive later.
The successful operative treatment of varicose veins depends on the ligation and division of all the main
tributaries of the great or small saphenous veins, to prevent a collateral venous circulation from developing, and
the ligation and division of all the perforating veins responsible for the leakage of high-pressure blood from the
deep to the superficial veins. It is now common practice to also remove or strip the superficial veins. Needless
to say, it is imperative to ascertain that the deep veins are patent before operative measures are taken.
Deep Vein Thrombosis andLong-Distance Air Travel
Passengers who sit immobile for hours on long-distance flights are very prone to deep vein thrombosis
in the legs. Preventative measures include stretching of the legs every hour to improve the venous circulation.,
Occlusions of the Popliteal, Anterior, and Posterior Tibial Arteries
Popliteal artery occlusion occurs just below the beginning of the artery (just below the opening in the
adductor magnus muscle). In some cases the occlusion extends distally to involve the origins of the anterior and
posterior tibial arteries and even the peroneal artery. Symptoms include intermittent claudication, night cramps,
and rest pain caused by ischemic neuritis. Signs include impaired or absent arterial pulses, lowered skin
temperature, color changes, muscle weakness, and trophic changes.
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