extensor digiti minimi muscle extensor digiti minimi muscle the extensor digiti minimi (extensor digiti quinti proprius) is a slender muscle of the forearm, placed on the ulnar side of the extensor digitorum communis, with which it is generally connected. extensor digiti minimithe synovial sheaths of the tendons on the back of the wrist. (extensor digiti quinti proprius labeled at center left.)detailsoriginthe anterior portion of the lateral epicondyle of the humerus (common extensor tendon)insertionat the extensor expansion, located at the base of the middle and distal phalanx of digit v on the dorsal sidearteryposterior interosseous arterynerveposterior interosseous nerve (c7, 8)actionsextends the wrist and the little finger at all jointsantagonistflexor digiti minimi brevisidentifierslatinmusculus extensor digiti minimita98a04.6.02.044ta22506fma38503anatomical terms of muscle it arises from the common extensor tendon by a thin tendinous slip and frequently from the intermuscular septa between it and the adjacent muscles. its tendon passes through a compartment of the extensor retinaculum, posterior to distal radio-ulnar joint, then divides into two as it crosses the dorsum of the hand, and finally joins the extensor digitorum tendon. all three tendons attach to the dorsal digital expansion of the fifth digit (little finger). there may be a slip of tendon to the fourth digit. variations 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 fifth 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. functions 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 forearm. it also extends the little finger, which means it straightens the little finger from a fist. additional images bones of left forearm. posterior aspect. posterior surface of the forearm. superficial muscles. transverse section across distal ends of radius and ulna. transverse section across the wrist and digits. extensor digiti minimi muscle extensor digiti minimi muscle ' extensor digiti minimi muscle muscles of hand. posterior view. muscles of hand. posterior view.