Short extensors of the toes

Topography and biomechanics of the short extensor

The muscle originates on the dorsal surface of the calcaneus, located laterally and anteriorly. Four narrow tendons extend from the muscle belly toward the digits of the foot.

The tendons insert onto the bases of the proximal, middle, and distal phalanges of the second through fifth digits. An important anatomical feature is that these tendons blend into the dorsal aponeurotic expansion (expansio dorsalis).

Muscle functions:

• Extension of digits II–V of the foot;
• Abduction of the lateral side of the foot.

Blood supply is provided by the lateral tarsal artery (a. tarsae lateralis) and the perforating branch of the fibular artery (r. perforans a. peroneae). The muscle is innervated by the deep fibular nerve — n. peroneus profundus (segments L₄–S₁).

Adjacent structures: plantar muscles

When studying extensors, it is important to understand the balance with antagonistic and stabilizing muscles of the plantar surface.

Adductor hallucis muscle (m. adductor hallucis) is a two-headed muscle that plays a key role in maintaining the transverse arch of the foot.

• Transverse head (caput transversum) originates from the deep transverse metatarsal ligaments and the capsules of the metatarsophalangeal (MTP) joints of digits III–V.
• Oblique head (caput obliquum) originates from the plantar surfaces of the cuboid and cuneiform bones, as well as the bases of metatarsals II–IV.

Both heads insert into the lateral sesamoid bone and the base of the proximal phalanx of digit I. The muscle adducts the big toe and flexes its proximal phalanx.

Plantar interossei muscles (mm. interossei plantares) consist of three bellies. They originate from the medial surfaces of metatarsals III–V and insert into the medial sides of the bases of the proximal phalanges of the same digits, blending into the dorsal aponeurosis.

Synovial sheaths of the foot and clinical significance

Important structures protecting the tendons are located on the plantar surface:

• Common flexor sheath of the digits (vagina tendinum mm. flexorum digitorum pedis) extends from the calcaneus along the medial sulcus, contains the tendons, and communicates with the sheath beneath the flexor retinaculum.
• Sheath of the flexor hallucis longus runs from behind the medial malleolus to digit I. At the level of the crossover with the tendons of the flexor digitorum longus (chiasma plantare), it gives off connecting bands (tendineae vincula).
• Digital synovial sheaths (II–V) are reinforced by short and long ligaments (vincula brevia et longa).

Clinical presentation: Knowledge of these spaces is critical. Infection can spread rapidly along the tendon sheaths. Tenosynovitis of the extensors and flexors also frequently develops here, and tarsal tunnel syndrome — compression of the tibial nerve (n. tibialis) — may occur in the area of the medial malleolus.

Class and exam questions

What else to study on this topic

• Two-headed structure of the adductor hallucis (oblique and transverse heads)
• Topography of the common tendon sheaths on the plantar surface
• Ligamentous apparatus of the digits of the foot: vincula brevia et longa
• Tarsal tunnel syndrome and anatomy of the medial malleolus
• Clinical significance of bursae in bursitis

Other topics in the "Myology" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.