Extensor Carpi Ulnaris, Medial View

Description

Running along the posteromedial border of the forearm, the extensor carpi ulnaris (ECU) is highlighted as a long fusiform belly that tapers into a tendon approaching the dorsoulnar wrist. From a medial vantage, its muscle mass sits posterior to the ulna and lies adjacent to the ulnar head and styloid process as it courses distally toward the base of the fifth metacarpal. Proximally, you would expect its attachments near the lateral epicondyle via the common extensor origin and along the posterior border of the ulna, with neighboring extensor digitorum and extensor digiti minimi positioned more laterally. Orientation is clear. The tendon passes deep to the extensor retinaculum in the sixth dorsal compartment. This angle matters because the ECU is more than a wrist extensor, it is a key dynamic stabilizer of the distal radioulnar joint and ulnar-sided wrist during gripping, forearm rotation, and ulnar deviation. Tendinopathy and tenosynovitis of the ECU are common in racquet sports and golf, and subluxation can occur when the ECU subsheath fails, often producing painful snapping during supination combined with ulnar deviation. The close relationship of the tendon to the ulnar groove, triangular fibrocartilage complex (TFCC), and dorsal sensory branch of the ulnar nerve makes this an efficient teaching view for localizing ulnar-sided wrist pain and planning a safe approach for ECU sheath repair or compartment release. Use this asset in upper limb anatomy labs to anchor the extensor compartment layout, in hand surgery texts discussing the sixth extensor compartment and DRUJ stability, or in sports medicine materials correlating physical exam maneuvers with ultrasound or MRI findings along the dorsoulnar wrist. Anatomical accuracy verified by SciePro's Medical Advisory Board.