Extensor Digitorum Longus

Origin

The extensor digitorum longus muscle originates from the:

- lateral condyle of tibia;

- proximal three quarters of fibula;

- anterior aspect of the adjacent interosseous membrane of leg.

Insertion

The fibers of the extensor digitorum longus muscle travel inferiorly to the foot and insert onto the:

- dorsal aspects of the bases of middle phalanges of the second, third, fourth, and little toes;

- dorsal aspects of the bases of distal phalanges of the same toes.

Key Features & Anatomical Relations

The extensor digitorum longus muscle is found in the anterior compartment of the leg. It is a long, thick, unipennate type of skeletal muscle. In the distal one third of the leg, the muscle belly gives rise to a tendon that travels deep to the superior and inferior extensor retinacula of the foot, where it passes through the tendinous sheath of extensor digitorum longus. At the ankle, it divides into four tendons. Along the dorsum of the foot, these tendons spread out as they travel to their respective toes. Along the dorsal aspects of the phalanges of the second, third, fourth and little toes, the tendons each form an aponeurotic extensor expansion, which then travel to their insertion sites.

The extensor digitorum longus muscle is located:

- anterior to the fibula and the extensor digitorum brevis, fibularis brevis and fibularis longus muscles;

- medial to the fibularis tertius muscle;

- lateral to the tibialis anterior and extensor hallucis longus muscles.

Actions & Testing

The extensor digitorum longus muscle is involved in multiple actions:

- extends the distal phalanges at the distal interphalangeal joints of the second, third, fourth and little toes;

- extends the middle phalanges at the proximal interphalangeal joints of the same toes;

- extends the proximal phalanges at the metatarsophalangeal joints of the same toes;

- dorsiflexes the foot at the ankle joint.

The extensor digitorum longus muscle can be tested by extending the second to fourth toes against resistance, during which its tendons can be seen and palpated (Standring, 2016).

References

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.