Short Intrinsics of the hand are Lumbricals and Interossei.
- There are four Lumbricals. (from Radial side I-IV)
- I and II Lumbricals have a single head and are innervated by the median nerve.
- III and IV Lumbricals have two heads and are innervated by the deep branch of the ulnar nerve.
- Lumbricals are able to flex the fingers at the MCP joint and extend the IP joint, but not at the same time.
When the lumbricals flex the MCP joint, the Extensor Digitorum extend the IP joint.