Opponens pollicis forms part of the thenar eminence. It arises from the tubercle of the trapezium and flexor retinaculum. From here it passes radially and distally. It inserts into the radial border of the palmar surface of the first metacarpal.
Usually, it is innervated by the recurrent branch of the median nerve (C8,T1). However, it may receive motor innervation from the deep branch of the ulnar nerve (T1).
Opponens pollicis has the action of opposing the thumb as exemplified by bringing into direct contact the pulps of thumb and little finger. It involves both medial rotation and flexion at the carpometacarpal and metacarpophalangeal joints of the thumb.