Muscles abducting / adducting / opposing the fingers

Palmar interossei

Dorsal interossei

Abductor digiti minimi

Opponens digiti minimi

Abductor digiti minimi

Abductor digiti minimi is the most superficial of the hypothenar muscles, lying in series with the dorsal interossei. It arises from the pisiform, the pisohamate and pisometacarpal ligaments, and the tendon of flexor carpi ulnaris, to insert by a tendon into the ulnar side of the proximal phalanx of the little finger and its dorsal digital expansion.

Nerve supply

Abductor digiti minimi is supplied by the deep branch of the ulnar nerve, root value C1.

Action

Abductor digiti minimi pulls the little finger away from the ring finger into a position of abduction. It also helps to flex the metacarpophalangeal joint.  By its attachment to the dorsal digital expansion, the muscle may help in extending the interphalangeal joints. Abductor digiti minimi is a powerful muscle playing an important role in grasping a large object with outspread fingers.

Opponens digiti minimi

Opponens digiti minimi lies deep to abductor digiti minimi, arising from the hook of the hamate and adjacent flexor retinaculum, to insert into the medial half of the palmar surface of the fifth metacarpal.

Nerve supply

Opponens digiti minimi is supplied by the deep branch of the ulnar nerve, root value T1.

Action

Opponens digiti minimi pulls the little finger forwards towards the palm and rotates it laterally at the carpometacarpal joint. This movement deepens the hollow of the hand, and is a necessary part of opposition of the little finger.

Palpation

The hypothenar muscles are closely related to one another; palpation of the individual muscles is therefore difficult. Resistance to abduction of the little finger enables abductor digiti minimi to be palpated on the ulnar border of the hand. For the movements of flexion and opposition of the little finger it is difficult to localize the action of the remaining hypothenar muscles, so accurate palpation is hard to achieve.