A Posterior View of the Extensor Carpi Ulnaris Muscles in a Male

Description

Running along the dorsoulnar forearm, the extensor carpi ulnaris (ECU) muscle belly sits superficial in the posterior compartment, lateral to the subcutaneous border of the ulna and medial to the extensor digitorum mass. Distally, its tendon narrows and tracks toward the ulnar head, passing posterior to the distal radioulnar joint and continuing to the base of the fifth metacarpal on the dorsum of the hand. The extensor retinaculum overlies the distal tendons at the wrist, and the ECU occupies the sixth dorsal compartment, a key landmark along the ulnar side. For wrist biomechanics, this view clarifies why ECU contributes to both wrist extension and ulnar deviation, and why it behaves differently from radial-sided extensors during forearm rotation. ECU tendon instability and subluxation occur with disruption of its subsheath, often after a forceful combination of supination, wrist flexion, and ulnar deviation, producing ulnar-sided wrist pain and a snapping sensation during rotation. It also helps orient the clinician to adjacent structures that are easily confused on exam, including the extensor carpi radialis longus and brevis tendons more radially and the extensor digiti minimi tendon just lateral to ECU at the distal forearm. Orthopaedic and sports medicine texts use this angle to teach dorsal wrist compartment anatomy, ECU subsheath pathology, and the relationship of the tendon to the ulnar head during distal radioulnar joint assessment. Anatomy faculty can pair it with surface anatomy labs to map the dorsoulnar wrist, guide palpation during resisted extension with ulnar deviation, and anchor ultrasound teaching for the sixth compartment. Anatomical accuracy verified by SciePro's Medical Advisory Board.