Abductor Pollicis Longus Muscle, Lateral View

Description

Seen from the lateral aspect with the forearm in supination, the abductor pollicis longus (Musculus abductor pollicis longus) runs along the posterior compartment of the forearm, deep to the more superficial extensor mass. Its muscular belly arises from the posterior surfaces of the ulna and radius and the intervening interosseous membrane, then tapers distally toward the radial side of the wrist. The tendon passes lateral to the distal radius and continues toward the base of the first metacarpal, placing it in close topographic relationship to the radial styloid, carpal bones, and thumb ray. Clear landmarks. Clinically, this lateral view helps orient the abductor pollicis longus within the first dorsal extensor compartment at the radial wrist, where it shares a synovial sheath with extensor pollicis brevis. That arrangement underlies de Quervain tenosynovitis, in which thickening of the compartment produces pain over the radial styloid and a positive Finkelstein test. For procedural teaching, the illustration also supports safe planning of injections or surgical release by clarifying the tendon’s course at the radial border of the wrist and its relationship to bony contours used as palpation guides. Use this asset in upper limb anatomy teaching for medical or allied health curricula when introducing the deep extensor layer, the thumb abductors, and the functional anatomy of radial deviation and thumb carpometacarpal mechanics. It also fits well in hand surgery, sports medicine, and rehabilitation materials discussing de Quervain disease, first dorsal compartment release, or differential diagnosis of radial-sided wrist pain. Anatomical accuracy verified by SciePro's Medical Advisory Board.