Abductor Pollicis Longus, Posterior View

Description

Running along the posterolateral forearm, the abductor pollicis longus (APL) is shown arising broadly from the posterior surfaces of the ulna and radius and the intervening interosseous membrane, then narrowing into a tendon that courses distally toward the radial side of the wrist. Near the distal radius, its tendon travels in the first dorsal extensor compartment, lying lateral to extensor pollicis longus and commonly sharing a sheath with extensor pollicis brevis. Deep to the extensor retinaculum, the APL tendon turns toward its insertion on the base of the first metacarpal, with the radial styloid and carpal bones providing clear osseous reference points. Orientation is posterior, with a lateral bias. That tendon course matters at the dorsoradial wrist. De Quervain tenosynovitis localizes to the first dorsal compartment, where thickening of the APL and extensor pollicis brevis synovial sheath produces pain over the radial styloid and a positive Finkelstein maneuver. Proximal to the retinaculum, the APL tendon can intersect the extensor carpi radialis longus and brevis tendons, a common setup for intersection syndrome in rowers, weightlifters, and manual workers. Small compartment septations and variable APL tendon slips are not trivia, they influence steroid injection placement and surgical release. Use this artwork for upper-limb anatomy teaching in gross anatomy or kinesiology when you need clean compartment-level organization of the posterior forearm extensors and their distal tendon paths across the wrist. It also fits orthopaedic or hand surgery materials describing first dorsal compartment release, dorsal wrist pain workup, and tendon sheath pathology. Anatomical accuracy verified by SciePro's Medical Advisory Board.