Abductor Pollicis Longus, Lateral View

Description

Arising from the posterior surfaces of the radius and ulna with fibers anchored along the interosseous membrane, the abductor pollicis longus (APL) runs distally and laterally toward the radial styloid in a lateral forearm view. Its muscle belly lies deep to the brachioradialis and extensor carpi radialis longus and brevis, then narrows into a tendon that crosses the wrist beneath the extensor retinaculum. At the dorsoradial wrist, the APL tendon sits in the first dorsal extensor compartment, typically sharing a synovial sheath with extensor pollicis brevis and passing superficial to the anatomic snuffbox region. Distal insertion is shown at the base of the first metacarpal, with frequent slips toward the trapezium. Clear orientation matters. Clinically, this lateral perspective is the one you want for teaching De Quervain tenosynovitis and steroid injection technique, because it clarifies how the APL and extensor pollicis brevis tendons crowd the first compartment at the radial styloid and why septations can make a single injection fail. The same tendon course explains intersection syndrome, where the APL (and extensor pollicis brevis) cross over extensor carpi radialis longus and brevis in the distal dorsal forearm, producing pain and crepitus a few centimeters proximal to the wrist. Surgeons planning first compartment release can also map nearby structures, including the superficial branch of the radial nerve and the radial artery just volar to the snuffbox. Use this asset in upper limb anatomy labs, hand surgery teaching files, and textbook figures on thumb abduction and carpometacarpal mechanics, or as a clean reference in patient education for De Quervain pathology and post release anatomy. Anatomical accuracy verified by SciePro's Medical Advisory Board.