Hypothenar muscles
Three muscles, innervated by the ulnar nerve, whose substance forms the contour of the hypothenar eminence on the hand's ulnar side.
Superficial to deep, the three muscles are the:
- abductor digiti minimi (ADM)
- crosses CMC and MP joints
- proximal attachment to pisiform.
- shares distal attachment with flexor digiti minimi on base of proximal phalanx.
If the ADM acts to abduct the fifth MP joint, the flexor carpi ulnaris (FCU) must act to stabilize the pisiform. FCU activity in turn produces wrist flexion and ulnar deviation. This may necessitate activity in ECRL/B.
- some fibers attach distally the fifth digit's extensor mechanism, so the ADM also contributes to PIP/DIP extension.
- flexor digiti minimi
- crosses CMC and MP joints
- opponens digiti minimi
- crosses only the CMC joint