Metacarpophalangeal joint of the ring finger is flexed by the lumbrical, palmar, and dorsal interosseous muscles, which are innervated by the ulnar nerve. Extensor digitorum, innervated by the radial nerve, extends this joint. Musculocutaneous and axillary nerves do not supply muscles of the hand. Median nerve supplies the lateral two lumbricals, which can flex metacarpophalangeal joints of the index and middle fingers.