Extensor digiti minimi extends the little finger and assists wrist extension.
The extensor digiti minimi is a slender muscle in the posterior compartment of the forearm that specifically extends the fifth digit (little finger). It is functionally a subdivision of the extensor digitorum, but often appears as a separate muscle with its own tendon. It plays a key role in independent extension of the little finger, especially during precise or expressive hand movements.
The extensor digiti minimi is situated on the posterolateral forearm, lying medial to the extensor digitorum and lateral to the extensor carpi ulnaris. Its tendon passes through its own compartment in the extensor retinaculum before reaching the dorsum of the hand.
The muscle arises as a distinct slip from the common extensor origin and becomes tendinous as it crosses the wrist.
The extensor digiti minimi contributes to:
Supplied by the posterior interosseous nerve (a continuation of the deep branch of the radial nerve), with roots from C7 and C8.
The muscle lies between the extensor digitorum laterally and the extensor carpi ulnaris medially. Its tendon travels superficial to the wrist extensors and has a dedicated tunnel in the extensor retinaculum. Distally, it merges with the extensor hood of the little finger.
While not easily visible externally, its tendon can be palpated on the dorsal-ulnar side of the wrist, especially during active extension of the little finger against resistance.
The extensor digiti minimi originates from the dorsal mass of the limb bud, alongside other extensors. Although often considered a split from the extensor digitorum embryologically, it usually differentiates into a separate structure during fetal development.
In some non-human primates, the extensor digiti minimi is not present as a distinct muscle. In humans, it has evolved to enhance fine motor control and independence of the fifth digit, reflecting the importance of digital dexterity in tool use and expression.