Front of Leg and Dorsum of Foot

Introduction

The leg is the part of the lower limb between the knee and the ankle. The foot lies below the ankle. It has two surfaces: the dorsum (superior surface) and the sole or plantar surface (inferior surface).

Most of the muscles, nerves, and blood vessels that pass through the front of the leg continue onto the dorsum of the foot. Therefore, the anterior compartment of the leg and the dorsum of the foot are usually studied together.

Compartments of Leg

The deep fascia of the leg sends strong fibrous septa to the tibia and fibula, dividing the leg into three compartments: anterior, lateral, and posterior. The deep fascia is firmly attached to the periosteum over the subcutaneous parts of the tibia and fibula, including the medial surface of the tibia and the medial and lateral malleoli.

The three compartments are:

1. Anterior compartment: It lies between the tibia, fibula, interosseous membrane, and the anterior intermuscular septum.
2. Lateral compartment: It is located between the anterior and posterior intermuscular septa, along the lateral side of the fibula.
3. Posterior compartment: It lies behind the tibia, fibula, and interosseous membrane, and is bounded by the posterior intermuscular septum.

Surface Landmarks

Bony Landmarks

• Medial and lateral condyles of the tibia: The medial and lateral condyles can be felt on either side of the patellar ligament, especially when the knee is flexed and the thigh is rotated laterally.
• Tibial tuberosity: The tibial tuberosity is a prominent bony projection on the front of the tibia, about 2.5 cm below the knee joint. It provides attachment to the patellar ligament.
• Anterior border of the tibia (shin): The anterior border of the tibia, commonly called the shin, is a sharp, curved bony ridge that can be felt just beneath the skin. It extends from the tibial tuberosity to the anterior border of the medial malleolus.
• Medial surface of the tibia: Most of the medial surface of the tibia is subcutaneous and can be easily felt. Its upper part provides insertion for the sartorius, gracilis, and semitendinosus muscles. The great saphenous vein crosses the lower one-third of this surface.
• Medial malleolus: The medial malleolus is the bony prominence on the inner side of the ankle.
• Head of the fibula: The head of the fibula is located on the posterolateral side of the leg, at the level of the tibial tuberosity.
• Neck of the fibula: The neck of the fibula lies just below the head of the fibula.
• Lateral malleolus: The lateral malleolus is the bony prominence on the outer side of the ankle. It extends about 0.5 cm lower than the medial malleolus.
• Peroneal trochlea: The peroneal trochlea can be felt as a small bony projection about one finger’s breadth below the lateral malleolus.
• Sustentaculum tali: The sustentaculum tali is a bony projection located about one thumb’s breadth below the medial malleolus.
• Tuberosity of the navicular bone: The navicular tuberosity can be felt about 3 to 4 cm in front of and below the medial malleolus.
• Tuberosity of the base of the fifth metatarsal: This is the most prominent bony landmark along the lateral border of the foot. It is located approximately midway between the heel and the base of the little toe.

Soft Tissues Landmarks

Calf prominence: The bulge of the calf is formed mainly by the gastrocnemius muscle with the soleus muscle beneath it.

Calcaneal (achilles) tendon: The calcaneal (achilles) tendon is a thick, strong tendon formed by the gastrocnemius, soleus, and plantaris muscles. It is easily felt behind the ankle.

Superficial Fascia of Front of the Leg and Dorsum of Foot

The superficial fascia of the front of the leg and the dorsum of the foot contains superficial veins, cutaneous nerves, and fat.

Superficial veins

The superficial veins of the front of the leg and dorsum of the foot include:

1. Dorsal digital veins
2. Medial marginal vein
3. Lateral marginal vein
4. Four dorsal metatarsal veins
5. Dorsal venous arch
6. Great saphenous vein
7. Small saphenous vein

Dorsal digital veins

Each toe has two dorsal digital veins, one on each side. The veins from adjacent toes join to form the four dorsal metatarsal veins. The dorsal digital vein on the medial side of the great toe continues as the medial marginal vein. The dorsal digital vein on the lateral side of the little toe continues as the lateral marginal vein.

Dorsal venous arch

The dorsal venous arch lies on the dorsum of the foot over the proximal parts of the metatarsal bones. It is formed by the union of the four dorsal metatarsal veins.

Great saphenous vein

The great saphenous vein is formed by the union of the medial end of the dorsal venous arch and the medial marginal vein.

Course

The vein passes upward in front of the medial malleolus. It then ascends along the medial side of the leg, crosses the lower one-third of the medial surface of the tibia, and continues upward toward the back of the knee before reaching the thigh.

Small saphenous vein

The small saphenous vein is formed by the union of the lateral end of the dorsal venous arch and the lateral marginal vein.

Course

The vein passes upward behind the lateral malleolus and then ascends along the back of the leg. Throughout its course in the leg, it is accompanied by the sural nerve.

Cutaneous Nerves

The skin of the front of the leg and the dorsum of the foot is supplied by the following cutaneous nerves:

1. Infrapatellar branch of the saphenous nerve
2. Saphenous nerve
3. Lateral cutaneous nerve of the calf
4. Superficial peroneal nerve
5. Digital branches of the medial and lateral plantar nerves

Infrapatellar branch of the saphenous nerve (l3, l4)

The infrapatellar branch arises from the saphenous nerve. It pierces the sartorius muscle and the fascia lata on the medial side of the knee. It then curves downward and forward to supply the skin over the patellar ligament. Along with branches of the femoral nerve and the saphenous nerve, it forms the patellar plexus.

Saphenous nerve (l3, l4)

The saphenous nerve is the largest cutaneous branch of the femoral nerve. It leaves the adductor canal by piercing the deep fascia between the sartorius and gracilis muscles. It then descends along the medial side of the leg in front of the great saphenous vein.

Distribution

The saphenous nerve:

• Contributes to the subsartorial plexus
• Gives off the infrapatellar branch
• Supplies the skin on the medial side of the leg
• Supplies the medial border of the foot up to the ball of the great toe

Lateral cutaneous nerve of the calf (l5, s1, s2)

The lateral cutaneous nerve of the calf is a branch of the common peroneal nerve. It pierces the deep fascia over the lateral head of the gastrocnemius and descends along the lateral side of the leg.

Distribution

It supplies the skin over the upper two-thirds of the lateral side of the leg.

Superficial peroneal nerve (l4, l5, s1)

The superficial peroneal nerve is a branch of the common peroneal nerve. It arises near the neck of the fibula and divides into medial and lateral branches in the lower part of the leg.

Distribution

It supplies:

• The skin over the lower one-third of the lateral side of the leg
• Most of the dorsum of the foot

It does not supply:

• The lateral border of the foot, which is supplied by the sural nerve
• The medial border of the foot up to the base of the great toe, which is supplied by the saphenous nerve
• The skin between the first and second toes, which is supplied by the deep peroneal nerve

Digital branches of the medial and lateral plantar nerves

The digital branches of the medial and lateral plantar nerves curve onto the dorsum of the toes. They supply the distal parts of the dorsal surfaces of the toes and the nail beds.

Deep Fascia

The deep fascia of the leg is a strong layer of connective tissue that surrounds the muscles and helps keep them in position during movement. It sends two intermuscular septa to the bones:

1. Anterior intermuscular septum
2. Posterior intermuscular septum

These septa divide the leg into three compartments:

• Anterior compartment
• Lateral compartment
• Posterior compartment

The deep fascia also gives rise to two transverse septa:

• Superficial transverse intermuscular septum
• Deep transverse intermuscular septum

These septa further divide the posterior compartment into:

• Superficial compartment
• Intermediate compartment
• Deep compartment

The deep fascia is firmly attached to the periosteum over the medial surface of the tibia and the subcutaneous surfaces of the medial and lateral malleoli.

Retinacula

Near the ankle joint, the deep fascia becomes thickened to form strong fibrous bands called retinacula. There are five retinacula around the ankle:

1. Superior extensor retinaculum
2. Inferior extensor retinaculum
3. Superior peroneal retinaculum
4. Inferior peroneal retinaculum
5. Flexor retinaculum

The retinacula hold the long tendons close to the bones and prevent them from bowstringing during movements of the foot and ankle.

Extensor Retinaculum

The extensor retinaculum is a thickening of the deep fascia in front of the ankle. It holds the extensor tendons close to the bones and prevents them from bowstringing during movements of the foot. It consists of two parts:

1. Superior extensor retinaculum
2. Inferior extensor retinaculum

Superior Extensor Retinaculum

The superior extensor retinaculum is a broad fibrous band located across the front of the ankle.

• Width: About 3 cm
• Attachments:
  • Medially: Lower part of the anterior border of the tibia
  • Laterally: Lower part of the anterior border of the fibula

On the medial side, the retinaculum splits to enclose the tendon of the tibialis anterior muscle.

Inferior Extensor Retinaculum

The inferior extensor retinaculum is a Y-shaped fibrous band located in front of the ankle and the upper part of the dorsum of the foot.

Parts

It has three parts:

• Stem
• Upper (proximal) band
• Lower (distal) band

Attachments

• Stem: Attached to the anterior non-articular part of the superior surface of the calcaneus, in front of the calcaneal sulcus.
• Upper band: Attached to the anterior border of the medial malleolus.
• Lower band: Blends with the plantar aponeurosis.

The upper band passes upward and medially, while the lower band passes downward and medially.

Structures Passing Deep to the Extensor Retinacula

From medial to lateral, the following structures pass beneath both extensor retinacula:

1. Tibialis anterior tendon
2. Extensor hallucis longus tendon
3. Anterior tibial artery
4. Deep peroneal nerve
5. Extensor digitorum longus tendon
6. Peroneus tertius tendon

(Mnemonic:The Himalayas Are Never Dry Places)

Anterior Compartment of Leg

The anterior compartment, also called the extensor compartment, is located in the front of the leg.

Boundaries

The anterior compartment is bounded by:

• Anteriorly: Deep fascia of the leg
• Posteriorly: Interosseous membrane
• Medially: Lateral surface of the shaft of the tibia
• Laterally: Anterior intermuscular septum

Contents

The anterior compartment contains the following structures:

Muscles

• Tibialis anterior
• Extensor hallucis longus
• Extensor digitorum longus
• Peroneus tertius

Artery

• Anterior tibial artery

Nerve

• Deep peroneal nerve

Muscles of Anterior Compartment of Leg

The anterior compartment of the leg contains four muscles:

1. Tibialis anterior
2. Extensor hallucis longus
3. Extensor digitorum longus
4. Peroneus tertius

Common Features

These muscles share several common features:

Actions

• All four muscles dorsiflex the ankle joint.
• When the foot is fixed on the ground during walking, they help pull the body forward over the foot.

Nerve Supply

All the muscles of the anterior compartment are supplied by the deep peroneal nerve.

Origin

• Tibialis anterior originates from the tibia.
• Extensor hallucis longus, extensor digitorum longus, and peroneus tertius originate mainly from the fibula.

Tibialis Anterior

The tibialis anterior is a spindle-shaped muscle with multipennate fibers. It is the largest muscle in the anterior compartment of the leg.

Origin

The tibialis anterior arises from:

1. Lateral condyle of the tibia
2. Upper two-thirds of the lateral surface of the shaft of the tibia
3. Anterior surface of the interosseous membrane
4. Overlying deep fascia

Course

The muscle fibers run vertically downward and form a broad tendon. This tendon passes beneath the superior and inferior extensor retinacula before reaching the foot.

Insertion

The tendon inserts into:

1. Medial and inferior surfaces of the medial cuneiform
2. Base of the first metatarsal

Nerve Supply

The tibialis anterior is supplied by the deep peroneal nerve.

Actions

The tibialis anterior performs the following actions:

1. Dorsiflexes the foot at the ankle joint (chief action)
2. Inverts the foot
3. Supports the medial longitudinal arch of the foot

Extensor Hallucis Longus

The extensor hallucis longus is a thin muscle located in the anterior compartment of the leg. Most of its upper part is covered by the tibialis anterior and extensor digitorum longus muscles.

Origin

The extensor hallucis longus arises from:

1. Posterior part of the middle half of the medial surface of the shaft of the fibula
2. Anterior surface of the interosseous membrane

Course

The muscle fibers run vertically downward and form a tendon that passes beneath the superior and inferior extensor retinacula before reaching the great toe.

Insertion

The tendon inserts into the dorsal surface of the base of the distal phalanx of the great toe.

Nerve Supply

The extensor hallucis longus is supplied by the deep peroneal nerve.

Actions

The extensor hallucis longus performs the following actions:

1. Dorsiflexes the foot at the ankle joint
2. Extends the great toe at both the metatarsophalangeal and interphalangeal joints

Clinical Testing

To test the extensor hallucis longus, ask the patient to extend the great toe against resistance. During this movement, the tendon of the muscle becomes prominent on the front of the ankle. It can be seen and felt just lateral to the tendon of the tibialis anterior.

Extensor Digitorum Longus

The extensor digitorum longus is a muscle of the anterior compartment of the leg. Its tendon passes beneath the extensor retinacula and divides into four tendons that supply the lateral four toes.

Origin

The extensor digitorum longus arises from:

1. Lateral condyle of the tibia
2. Upper one-fourth and the medial part of the middle half of the medial surface of the fibula
3. Anterior surface of the interosseous membrane

Course

The muscle fibers pass downward and medially to form a tendon that runs beneath the superior and inferior extensor retinacula. On the dorsum of the foot, the tendon divides into four slips, one for each of the second to fifth toes.

Insertion

The four tendons insert into the middle and distal phalanges of the second, third, fourth, and fifth toes. At the metatarsophalangeal joints, the tendons to the second, third, and fourth toes are joined on the lateral side by the tendons of the extensor digitorum brevis, forming the dorsal digital expansion.

Nerve Supply

The extensor digitorum longus is supplied by the deep peroneal nerve.

Actions

The extensor digitorum longus performs the following actions:

1. Dorsiflexes the foot at the ankle joint
2. Extends the second to fifth toes at the metatarsophalangeal, proximal interphalangeal, and distal interphalangeal joints

Clinical Testing

To test the extensor digitorum longus, ask the patient to extend the second to fifth toes against resistance. The tendons of the muscle become prominent on the dorsum of the foot during this movement.

Peroneus Tertius

The peroneus tertius is a small muscle in the anterior compartment of the leg. It is often considered a part of the extensor digitorum longus muscle.

Origin

The peroneus tertius arises from:

1. Lower one-fourth of the medial surface of the shaft of the fibula
2. Anterior surface of the interosseous membrane

Course

The muscle fibers descend to form a tendon that passes beneath the superior and inferior extensor retinacula. The tendon lies lateral to the tendon of the extensor digitorum longus.

Insertion

The tendon inserts into the medial part of the dorsal surface of the base of the fifth metatarsal.

Nerve Supply

The peroneus tertius is supplied by the deep peroneal nerve.

Actions

The peroneus tertius performs the following actions:

1. Dorsiflexes the foot at the ankle joint along with the extensor digitorum longus
2. Everts the foot along with the peroneus longus and peroneus brevis

Anterior Tibial Artery

The anterior tibial artery is the main artery of the anterior compartment of the leg. It supplies blood to the muscles and other structures in this compartment. The anterior tibial artery is similar to the posterior interosseous artery of the forearm. It also receives additional blood supply from the perforating branches of the peroneal artery.

Beginning

The anterior tibial artery begins at the lower border of the popliteus muscle as one of the two terminal branches of the popliteal artery.

Course

The artery begins in the posterior compartment of the leg. It passes through an opening in the interosseous membrane to enter the anterior compartment. It then descends vertically along the front of the leg toward the ankle.

Termination

At the level midway between the medial and lateral malleoli, the anterior tibial artery continues as the dorsalis pedis artery.

Relations

The position of the artery changes as it descends through the leg.

• Upper one-third of the leg: the artery lies between the tibialis anterior and extensor digitorum longus muscles.
• Middle one-third of the leg: the artery lies between the tibialis anterior and extensor hallucis longus muscles.
• Lower one-third of the leg: the artery lies between the extensor hallucis longus and extensor digitorum longus tendons.

The tendon of the extensor hallucis longus crosses in front of the artery from the lateral side to the medial side.

The deep peroneal nerve lies:

• Lateral to the artery in the upper and lower thirds of the leg.
• Anterior to the artery in the middle third of the leg.

Branches

The anterior tibial artery gives off the following branches:

1. Anterior tibial recurrent artery
2. Posterior tibial recurrent artery
3. Muscular branches
4. Anterior medial malleolar artery
5. Anterior lateral malleolar artery

The anterior and posterior tibial recurrent arteries take part in the arterial anastomosis around the knee joint. The anterior medial and anterior lateral malleolar arteries contribute to the arterial anastomosis around the ankle joint.

Venous accompaniment

The anterior tibial artery is accompanied throughout its course by a pair of venae comitantes.

Deep Peroneal Nerve

The deep peroneal nerve is the main nerve of the anterior compartment of the leg and the dorsum of the foot.

Root value

The deep peroneal nerve is formed from the spinal nerve roots l4, l5, s1, and s2.

Beginning

The deep peroneal nerve is one of the two terminal branches of the common peroneal nerve. It begins near the neck of the fibula, beneath the peroneus longus muscle.

Course

The nerve starts on the lateral side of the neck of the fibula. It pierces the anterior intermuscular septum to enter the anterior compartment of the leg. It then passes through the extensor digitorum longus muscle and descends with the anterior tibial artery toward the ankle. In the middle one-third of the leg, the nerve moves toward the front of the artery but does not cross it completely. It finally remains on the lateral side of the artery. Because of this characteristic course, it is sometimes called the nervus hesitans (“hesitating nerve”).

Termination

In front of the ankle, on the dorsum of the foot, the deep peroneal nerve divides into:

• Medial terminal branch
• Lateral terminal branch

Branches and distribution

Muscular branches

The deep peroneal nerve supplies all four muscles of the anterior compartment of the leg:

• Tibialis anterior
• Extensor digitorum longus
• Extensor hallucis longus
• Peroneus tertius

Terminal branches

Lateral terminal branch

• Passes beneath the extensor digitorum brevis muscle
• Supplies the extensor digitorum brevis
• Supplies the tarsal and metatarsal joints
• Ends in a small enlargement called the pseudoganglion

Medial terminal branch

• Runs forward on the dorsum of the foot
• Supplies the skin of the first interdigital cleft (between the great toe and the second toe)

Important point

The deep peroneal nerve is the lower limb counterpart of the posterior interosseous nerve in the forearm.

Dorsum of Foot

Sensory Innervation of the Dorsum of Foot

The skin on the dorsum of the foot is supplied by four nerves:

1. Superficial peroneal nerve: this is a branch of the common peroneal nerve. It supplies most of the skin on the dorsum of the foot, except the area between the first and second toes.
2. Deep peroneal nerve: this is also a branch of the common peroneal nerve. It supplies the first interdigital cleft, which is the skin between the great toe and the second toe.
3. Sural nerve: this is a branch of the tibial nerve. It supplies the lateral border of the dorsum of the foot and the little toe.
4. Saphenous nerve: this is a branch of the femoral nerve. It supplies the medial border of the dorsum of the foot up to the head of the first metatarsal.

Muscles of the dorsum of the foot

The muscles on the dorsum of the foot are divided into two groups:

Extrinsic muscles: These muscles originate in the leg, and their tendons pass onto the dorsum of the foot. They include:

• Tibialis anterior
• Extensor hallucis longus
• Extensor digitorum longus
• Peroneus tertius

Intrinsic muscle: The only intrinsic muscle on the dorsum of the foot is the extensor digitorum brevis.

Extensor digitorum brevis

The extensor digitorum brevis is a thin muscle located on the lateral side of the dorsum of the foot. It lies deep to the tendons of the extensor digitorum longus.

Origin

The extensor digitorum brevis arises from the anterior part of the superior surface of the calcaneus.

Course

The muscle forms four tendons that run forward and medially beneath the tendons of the extensor digitorum longus. The most medial tendon is called the extensor hallucis brevis because it passes to the great toe.

Insertion

• First tendon (extensor hallucis brevis): inserts into the dorsal surface of the base of the proximal phalanx of the great toe.
• Second to fourth tendons: join the lateral side of the tendons of the extensor digitorum longus to form the dorsal digital expansions of the second, third, and fourth toes.

Nerve supply

The extensor digitorum brevis is supplied by the lateral terminal branch of the deep peroneal nerve.

Actions

• The extensor hallucis brevis extends the metatarsophalangeal joint of the great toe.
• The lateral three tendons assist the extensor digitorum longus in extending the metatarsophalangeal and interphalangeal joints of the second, third, and fourth toes, especially when the foot is dorsiflexed.

Dorsalis Pedis Artery

The dorsalis pedis artery is the main artery on the dorsum of the foot. It is an important artery that is routinely examined to assess the blood supply to the foot, especially in patients with peripheral arterial disease.

Beginning

The dorsalis pedis artery is the continuation of the anterior tibial artery. It begins in front of the ankle joint, midway between the medial and lateral malleoli.

Course

The artery runs forward along the medial side of the dorsum of the foot toward the first intermetatarsal space. It then passes between the two heads of the first dorsal interosseous muscle and enters the sole of the foot.

Termination

In the sole of the foot, the dorsalis pedis artery joins the lateral plantar artery to complete the plantar arterial arch.

Relations

Superficial

• Inferior extensor retinaculum
• Extensor hallucis brevis muscle, which crosses the artery from the lateral side to the medial side

Deep

• Ankle joint
• Talus
• Navicular bone
• Intermediate cuneiform bone

Medial

• Tendon of the extensor hallucis longus

Lateral

• First tendon of the extensor digitorum longus

Branches

The dorsalis pedis artery gives off the following branches:

1. Lateral tarsal artery
2. Medial tarsal arteries
3. First dorsal metatarsal artery
4. Arcuate artery

Key description

• Lateral Tarsal Artery: The lateral tarsal artery arises over the navicular bone and passes deep to the extensor digitorum brevis muscle. It contributes to the lateral malleolar arterial network.
• Medial Tarsal Arteries: There are two or three medial tarsal arteries. They supply the medial side of the foot and take part in forming the medial malleolar arterial network.
• First Dorsal Metatarsal Artery: This artery arises just before the dorsalis pedis artery enters the sole. It gives dorsal digital arteries to:
  • The medial side of the great toe
  • The adjacent sides of the first and second toes

• Arcuate Artery: The arcuate artery arises opposite the medial cuneiform bone. It runs laterally across the bases of the metatarsal bones, deep to the tendons of the extensor digitorum longus and extensor digitorum brevis. It gives rise to the second, third, and fourth dorsal metatarsal arteries. Each of these arteries divides into dorsal digital arteries that supply the adjacent sides of the toes.

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