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Extensor Digitorum Longus

The extensor digitorum longus (EDL) is the most lateral muscle of the anterior compartment of the leg.

The four muscles in the anterior compartment of the leg are the tibialis anterior, extensor digitorum longus, extensor hallucis longus, and fibularis tertius.

See Also: Anterior Compartment of the Leg

Extensor Digitorum Longus Anatomy

Origin

A small part of the origin of the muscle is to the lateral tibial condyle; however, most of it originate from the medial surface of the fibula and the superior part of the anterior surface of the interosseous membrane.

The EDL 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.

See Also: Flexor Digitorum Longus

Insertion

Each tendon of extensor digitorum longus forms a membranous extensor expansion (dorsal aponeurosis) over the dorsum of the proximal phalanx of the toe, which divides into two lateral bands and one central band. The central band inserts into the base of the middle phalanx, and the lateral slips converge to insert into the base of the distal phalanx.

Innervation

The extensor digitorum longus is innervated by the deep peroneal nerve (L4, L5, S1) (L4, L5, S1).

Blood Supply

Its blood supply comes from the Anterior tibial artery.

Action

EDL acts to extend toes 2 – 5 and dorsiflexes ankle joint.

Origin	Lateral tibial condyle Proximal 3/4 of anterior fibula Upper part of interosseous membrane Fascia cruris Anterior intermuscular septum
Insertion	Splits into 4 tendon slips after inferior extensor retinaculum, each of which insert on dorsum of middle and distal phalanges as part of extensor expansion complex
Innervation	Deep peroneal nerve (L4, L5, S1) (L4, L5, S1)
Blood Supply	Anterior tibial artery
Action	Extend toes 2 – 5 and dorsiflexes ankle joint

Extensor digitorum longus tends to be overactive and tight to compensate for an inhibited tibialis anterior. Stretching and myofascial release of the muscle together with activation tibialis anterior is indicated to regain muscle balance and improve functional ankle dorsiflexion.

To test the extensor digitorum longus, the lateral four toes are dorsiflexed against resistance; if acting normally, the tendons can be seen and palpated.