It is of a triangular form, and placed immediately beneath the palmaris brevis, abductor digiti minimi and flexor digiti minimi brevis.

[1] It arises from the convexity of the hamulus of the hamate bone and the contiguous portion of the transverse carpal ligament; it is inserted into the whole length of the metacarpal bone of the little finger, along its ulnar margin.

The opponens digiti minimi muscle serves to flex and laterally rotate the 5th metacarpal about the 5th carpometacarpal joint, as when bringing the little finger and thumb into opposition.

It is innervated by the deep branch of the ulnar nerve.

This article incorporates text in the public domain from page 464 of the 20th edition of Gray's Anatomy (1918)