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Extensor indicis

The extensor indicis (Latin: musculus extensor indicis) is a relatively flat, narrow muscle of the forearm that extends between the ulna and the phalanges of the second finger. It belongs to the posterior compartment of the forearm muscles, lying in the second (deep) layer. The extensor indicis acts at all joints of the index finger.

Extensor indicis
Origin Distal one-third of posterior surface of ulna, interosseous membrane of forearm
Insertion Bases of middle and distal phalanges of 2nd finger
Action Extension of 2nd finger
InnervationPosterior interosseous nerve of radial nerve (C7, C8)
Blood supply Anterior and posterior interosseous arteries
Forearm muscles (colored), Upper extremity, Muscles, Human arm, Anteromedial view, Dorsolateral view
Muscles of forearm by



The extensor indicis muscle originates from the distal one-third of the posterior surface of the ulna and interosseous membrane of the forearm.

Extensor indicis, Origin of extensor indicis, Insertion of extensor indicis, Forearm muscles, Muscles of the forearm, Posterior compartment muscles, Posterior compartment of the forearm, Arm muscles, Muscles of upper limb, Human arm, Human muscles
Origin of extensor indicis by



The extensor indicis descends to reach the second finger. It inserts on the bases of the middle and distal phalanges of the second digit of the hand.



The extensor indicis muscle extends the second finger at the metacarpophalangeal and interphalangeal joints of the index finger.



The extensor indicis is innervated by the posterior interosseous nerve, which is a branch of the radial nerve (C7, C8).


Blood supply

The extensor indicis muscle receives arterial blood supply from the anterior and posterior interosseous arteries. Both are branches of the common interosseous artery.