Extensor Digiti Minimi
The extensor digiti minimi (extensor digiti quinti proprius) is a slender muscle of the forearm, originated from common extensor tendon off lateral epicondyle. It inserts to tendon of extensor digitorum at proximal phalanx of little finger & into dorsal expansion of finger extensor tendons, and it is placed on the ulnar side of the Extensor digitorum communis, with which it is generally connected. The extensor digiti minimi extends proximal phalanx of little finger at MP joint & assists wrist extension, and also, extends the middle and distal phalanges especially when proximal phalanx is held in flexion. It arises from the common Extensor tendon by a thin tendinous slip, from the intermuscular septa between it and the adjacent muscles. Its tendon runs through a compartment of the dorsal carpal ligament behind the distal radio-ulnar joint, then divides into two as it crosses the hand, and finally joins the expansion of the Extensor digitorum communis tendon on the dorsum of the first phalanx of the little finger. The extensor digiti minimi is a two joint muscle. It acts as an extensor in both joints. It extends the wrist, which means it moves the back of the hand toward the back of the forarm. An additional fibrous slip from the lateral epicondyle; the tendon of insertion may not divide or may send a slip to the ring finger. Absence of muscle rare; fusion of the belly with the Extensor digitorum communis not uncommon. Variations to the 5th extensor compartment, which the extensor digiti minimi runs through, may cause tenosynovitis and can limit the use of the extensor digiti minimi. Extensor digiti minimi can also be bifurcated, which means split, at many different points in the muscle.