Abductor Pollicis Longus Under the Skin, Posterior View

Description

Running obliquely across the posterior forearm, the abductor pollicis longus (APL) arises from the posterior surfaces of the ulna and radius and the intervening interosseous membrane, then courses distally and laterally toward the radial styloid. Near the dorsal wrist crease its tendon becomes superficial beneath the superficial fascia and extensor retinaculum, occupying the first extensor compartment alongside the extensor pollicis brevis, with the extensor pollicis longus lying more dorsomedially as it angles around Lister’s tubercle. Deep to the muscle belly sit the radius and ulna, while adjacent dorsal compartment tendons, such as extensor carpi radialis longus and brevis laterally and extensor carpi ulnaris on the ulnar side, frame the overall extensor anatomy. Key landmarks. Because the APL tendon emerges at the radial aspect of the dorsal wrist, this posterior view maps directly onto the palpated anatomy of the anatomic snuffbox and the first dorsal compartment where stenosing tenosynovitis causes radial-sided pain with thumb motion. De Quervain tenosynovitis targets the APL and extensor pollicis brevis sheaths, and a teaching image that clarifies their relationship to the extensor retinaculum helps explain why compartment release must address septation and why symptoms localize just proximal to the radial styloid. The same corridor matters in intersection syndrome, where the APL and extensor pollicis brevis cross over the extensor carpi radialis longus and brevis tendons more proximally. Use this illustration in upper limb anatomy and kinesiology modules to teach thumb abduction mechanics, dorsal wrist compartment organization, and surface marking around the radial styloid. It also supports surgical education for first dorsal compartment release, tendon transfer planning, and clinical documentation of radial-sided wrist pain patterns. Anatomical accuracy verified by SciePro's Medical Advisory Board.