Extensor Carpi Ulnaris Muscle, Posterior View

Description

Running along the dorsoulnar forearm, the extensor carpi ulnaris is isolated in red against the posterior arm and hand skeleton. Proximally, its muscle belly arises from the lateral epicondyle of the humerus and the posterior border of the ulna, then narrows distally into a tendon that courses toward the ulnar side of the wrist to insert on the base of the fifth metacarpal. Deep to its line of pull, the ulna lies medial to the radius in anatomical position, with the carpal bones, metacarpals, and phalanges aligned distal to the distal radioulnar and radiocarpal joints. Bony landmarks stay readable. A posterior perspective on extensor carpi ulnaris matters because the tendon transitions from a relatively mobile forearm structure to a constrained wrist structure within the sixth dorsal compartment under the extensor retinaculum, a common site of tenosynovitis and painful snapping. Surgeons and sports clinicians also use its relationship to the distal ulna and the triangular fibrocartilage complex (TFCC) when evaluating ulnar sided wrist pain, distal radioulnar joint instability, or ECU subsheath injury after forceful supination with ulnar deviation. For teaching, the view cleanly separates ECU from extensor carpi radialis longus and brevis, reinforcing how ulnar deviation can be produced even in wrist extension. Ideal for upper limb anatomy labs, kinesiology and biomechanics lectures on wrist coupling, and hand therapy materials explaining resisted ECU testing and palpation along the dorsoulnar wrist. It also suits orthopedic and radiology publications discussing the sixth extensor compartment and the clinical exam of ulnar sided wrist pain. Anatomical accuracy verified by SciePro's Medical Advisory Board.