Lumbrical action

Lumbrical action is to hold a pea, that is to flex the metacarpophalangeal joint and extend the interphalangeal joints. When look at hand in this position, can see this makes an “L” shape, since L is for Lumbrical.

- intrinsics of hand are supplied by distal branches of ulnar and median nerves;
- hence, injury to both these nerves, esp ulnar nerve (distally), leads to imbalance between the extrinsic and intrinsic muscles;
- lumbricals are prime flexors of MP joints;
- they are responsible for well-synchronized flexion of MP joint w/ flexion of the interphalangeal (IP) joints;
- lumbricals, further, in conjugation with the interossei, form that part of the extensor expansion that is chiefly responsible for extension of
the proximal and distal interphalangeal joints;