Dorsum of Foot

Introduction

Introduction to the Dorsum of the Foot

The dorsum of the foot is the superior (upper) surface of the foot, extending from the anterior aspect of the ankle to the toes. It is primarily a tendinous and neurovascular region, containing the tendons of the extensor muscles from the anterior compartment of the leg, an intrinsic muscle (extensor digitorum brevis), and the terminal branches of the anterior tibial and superficial fibular nerves. The arterial supply is from the dorsalis pedis artery, a continuation of the anterior tibial artery, which provides the palpable dorsalis pedis pulse. The dorsal venous arch and the origins of the great and small saphenous veins are also located here. The skin is thin and mobile, allowing for easy access to underlying structures, but also predisposing to injury and infection. This region is essential clinically for assessment of vascular and neurological status of the lower limb.

Study

1. Surface Anatomy and Boundaries

The dorsum of the foot is bounded proximally by the ankle joint line and the inferior extensor retinaculum, and distally by the bases of the toes. Medially, the skin reflects the contour of the medial cuneiform and first metatarsal; laterally, it overlies the cuboid and fifth metatarsal. Key palpable landmarks include the navicular tuberosity (medially), the base of the fifth metatarsal (laterally), and the extensor hallucis longus tendon, which becomes prominent when the great toe is dorsiflexed. The skin is relatively thin, with little subcutaneous fat, making veins, tendons, and the dorsalis pedis artery easily accessible.

2. Bones and Joints

The bony framework of the dorsum includes the distal parts of the tibia and fibula forming the ankle mortise, the talus (which is mostly covered by the trochlea on the dorsum), the calcaneus (limited to the anterior aspect), the navicular, the cuboid, the three cuneiforms, and the five metatarsals. The joints visible on the dorsum are the talonavicular joint, the naviculocuneiform joints, the cuneometatarsal joints (tarsometatarsal or Lisfranc joint), and the metatarsophalangeal joints. The interphalangeal joints of the toes are also part of the dorsal surface.

The extensor tendons pass over these bones and joints, held in place by the inferior extensor retinaculum (a Y-shaped band) and the extensor hoods at the metatarsophalangeal joints. The dorsalis pedis artery lies on the tarsal bones, directly palpable between the extensor hallucis longus and extensor digitorum longus tendons.

3. Muscles of the Dorsum

There are two intrinsic muscles on the dorsum of the foot: the extensor digitorum brevis and the extensor hallucis brevis. They form a single muscle belly that originates from the anterior part of the superior and lateral surfaces of the calcaneus, and from the inferior extensor retinaculum. The muscle belly splits into four tendons: the most medial tendon inserts into the dorsal surface of the base of the proximal phalanx of the great toe (extensor hallucis brevis), and the remaining three tendons join the lateral sides of the extensor digitorum longus tendons to the second, third, and fourth toes. These muscles extend the metatarsophalangeal and interphalangeal joints of the respective toes. They are innervated by the lateral terminal branch of the deep fibular nerve (L5, S1).

Additionally, the tendons from the anterior compartment of the leg cross the dorsum: tibialis anterior (inserting on the medial cuneiform and first metatarsal), extensor hallucis longus (great toe distal phalanx), extensor digitorum longus (toes 2–5 via dorsal expansions), and peroneus tertius (fifth metatarsal base). These are not intrinsic to the foot but lie within the superficial layers of the dorsum.

4. Neurovascular Structures

Arterial supply: The dorsalis pedis artery is the direct continuation of the anterior tibial artery. It begins at the level of the ankle, midway between the malleoli, and runs forward on the dorsum of the foot, between the extensor hallucis longus and extensor digitorum longus tendons. It gives off several branches: the lateral tarsal artery (which contributes to the arcuate artery when present), medial tarsal arteries, the arcuate artery (inconstant, giving off the second, third, and fourth dorsal metatarsal arteries), and the first dorsal metatarsal artery. The dorsalis pedis artery then dives between the two heads of the first dorsal interosseous muscle to join the deep plantar arch in the sole. The arcuate artery, when present, loops laterally across the bases of the metatarsals and gives rise to the dorsal metatarsal arteries, which supply the toes. The dorsal metatarsal arteries give off dorsal digital branches.

Venous drainage: The dorsal venous arch lies in the superficial fascia over the metatarsals. It receives blood from dorsal digital veins and drains medially into the great saphenous vein (anterior to the medial malleolus) and laterally into the small saphenous vein (posterior to the lateral malleolus). Deep veins accompany the arteries as venae comitantes.

Nerves: (1) Deep fibular (peroneal) nerve – enters the dorsum under the extensor retinaculum, lateral to the dorsalis pedis artery. It supplies the extensor digitorum brevis and extensor hallucis brevis, then continues as a sensory branch to the first web space (skin between the great and second toes). (2) Superficial fibular nerve – pierces the deep fascia in the distal leg and divides into the medial and intermediate dorsal cutaneous nerves, which supply the skin of the dorsum except the first web space and the lateral border of the foot. (3) Sural nerve – supplies the lateral margin of the foot and the fifth toe. (4) Saphenous nerve – supplies the medial side of the foot up to the ball of the great toe.

5. Clinical Relevance

Palpation of the dorsalis pedis pulse: This is a standard part of the peripheral vascular examination. The artery is felt just lateral to the extensor hallucis longus tendon, at the level of the navicular bone. An absent pulse may indicate peripheral arterial disease, but congenital absence of the dorsalis pedis artery (via a dominant lateral tarsal artery or absence) occurs in a small percentage of the population. Comparison with the contralateral foot is important.

Foot drop and nerve injury: Injury to the deep fibular nerve causes loss of dorsiflexion and toe extension, and sensory loss in the first web space. The extensor digitorum brevis muscle may atrophy, producing a visible hollow on the lateral dorsum. This can be assessed by asking the patient to extend the toes against resistance.

Extensor tendon injuries: Lacerations over the dorsum can sever the extensor tendons, leading to inability to extend the corresponding toe or the foot. Surgical repair is often required. The proximity of the tendons to the skin and the lack of thick subcutaneous tissue make them vulnerable.

Ganglion cysts: The dorsum of the foot is a common location for ganglion cysts, especially near the extensor tendons or joints. These present as smooth, fluctuant swellings that transilluminate.

Dorsal foot wounds: In diabetic patients, neuropathy and ischemia can lead to ulcers on the dorsum, particularly over bony prominences. Assessment of the dorsalis pedis pulse and sensation (monofilament testing) is key.

Lisfranc injuries: Although primarily a tarsometatarsal joint injury, significant swelling and ecchymosis on the dorsum, especially with plantar ecchymosis, is a classic sign. The dorsalis pedis artery may be compromised due to its position over the tarsometatarsal joint, leading to ischemia.

Summary

Summary of the Dorsum of the Foot

The dorsum of the foot is a superficial region containing the extensor tendons, the extensor digitorum brevis muscle, and terminal neurovascular structures. The dorsalis pedis artery (from anterior tibial) is the main arterial supply and provides a palpable pulse point. The deep fibular nerve innervates the intrinsic muscles and supplies the first web space. Superficial veins form the dorsal venous arch, draining into the great and small saphenous veins. The sensory nerves are the superficial fibular (most of dorsum), sural (lateral border), and saphenous (medial border). Common clinical issues include pulse assessment, nerve injury, tendon lacerations, and diabetic foot ulcers.