[TA] muscle of posterior (extensor) compartment of forearm; origin, lateral epicondyle of humerus; insertion, by four tendons into the bases of the middle and distal phalanges; action, extends fingers, especially at metacarpophalangeal joint; nerve supply, radial (posterior interosseous). SYN: musculus extensor digitorum [TA], extensor (muscle) of fingers, musculus extensor digitorum communis.