Opponens digiti minimi flexes and laterally rotates the fifth metacarpal to oppose the little finger.
The opponens digiti minimi is one of the three muscles in the hypothenar eminence of the hand. It lies deep to both the abductor digiti minimi and the flexor digiti minimi brevis, and it functions to oppose the little finger by flexing and laterally rotating the fifth metacarpal bone. This movement allows the fifth digit to meet the thumb, enhancing grip and hand dexterity.
The opponens digiti minimi is located on the ulnar side of the palm, deep within the hypothenar compartment. It lies directly on the fifth metacarpal bone and is covered superficially by the other two hypothenar muscles.
This small, triangular muscle originates from the flexor retinaculum and hamate, and inserts along the shaft of the fifth metacarpal.
The opponens digiti minimi contributes to:
Supplied by the deep branch of the ulnar nerve (C8–T1).
The opponens digiti minimi is deep to both the abductor digiti minimi and the flexor digiti minimi brevis. It lies directly on the fifth metacarpal bone. The ulnar nerve and artery pass medial and deep to it before entering the deep palm.
Although not visible externally, the muscle contributes to the shape and depth of the hypothenar eminence. Its activity becomes apparent when cupping the palm or opposing the little finger toward the thumb.
The opponens digiti minimi originates from the ulnar (postaxial) part of the embryonic hand mesenchyme. Its action and innervation are consistent with other deep muscles of the hypothenar group.
In many non-human species, the opponens digiti minimi is rudimentary or absent. In humans, its presence reflects the evolutionary development of fine motor control and enhanced opposition between the thumb and little finger — crucial for complex tool use and firm cylindrical grips.