Lumbricals are tiny, intrinsic muscles in the fingers and toes. They facilitate the flexing of specific joints in the hands and feet, and provide connectivity with other joints. These muscles are distinct from other muscles because instead of being anchored on the bones, they are connected to tendons extending from other muscles. The movement of the major joints in hands at the base of the fingers is facilitated with these muscles as they are placed beneath the joints. In case of inter-phalangeal joints, they help in extending or straightening of the joint. In the hands, the medial nerve innervates the first two finger joints and the ulnar nerve innervates the third and fourth. The blood supply to these muscles comes from four different sources, including the dorsal and palmar digital arteries. In the feet, these muscles act as an appendage to the tendons, with each muscle except the first originating from two tendons. All four Lumbricals extend into the phalange hoods, thereby making an extension at the interphalangeal joints.
Written and medically reviewed by the Healthline Editorial Team
In Depth: Lumbricals