The lumbricals (also lumbrical muscles, latin: musculi lumbricales) are four intrinsic muscles of the hand that belong to the medial muscle group of the hand.
The lumbricals originate from tendons of the flexor digitorum profundus.
The lumbricals insert into the extensor digitorum tendons and also onto the proximal phalanges of the second to fifth digits of the hand.
The functions of the lumbricals are flexion of the proximal phalanges and extension of the medial and distal phalanges of the second, third, fourth and fifth fingers.
The first and second lumbricals (lumbricals I, II) of the hand are innervated by the median nerve, while the third and fourth (lumbricals III, IV) are innervated by the ulnar nerve.