Extensor Pollicis Brevis Muscle, Lateral View

Description

Arising from the posterior surface of the radius and the adjacent interosseous membrane, the extensor pollicis brevis lies on the dorsolateral forearm, deep to the brachioradialis proximally and lateral to the extensor digitorum. Its tendon courses distally along the radial (thumb) side, passing with the abductor pollicis longus in the first dorsal (extensor) compartment at the level of the radial styloid. Distally, the tendon inserts on the dorsal base of the proximal phalanx of the thumb, just distal to the first metacarpal, with the radius lateral to the ulna and the carpal, metacarpal, and phalangeal bones clearly oriented in a lateral projection. Short and direct. That tendon path matters because it defines the surface anatomy of the anatomical snuffbox region and the mechanics of thumb extension at the metacarpophalangeal joint, which you can contrast cleanly against extensor pollicis longus, the primary extensor of the interphalangeal joint. Pain and crepitus at the radial styloid in de Quervain tenosynovitis localizes to the shared synovial sheath of extensor pollicis brevis and abductor pollicis longus in the first dorsal compartment, a frequent target for ultrasound-guided injection or surgical release. The lateral view also helps teach why thumb extension can be weakened even when wrist extension remains preserved, given the separate innervation patterns of the posterior interosseous nerve branches to the deep extensors. Use this asset in upper limb anatomy teaching for osteology-to-myology correlation, in hand surgery texts illustrating the first dorsal compartment, or in rehabilitation materials explaining thumb extensor tendinopathy and post-release therapy cues. Anatomical accuracy verified by SciePro's Medical Advisory Board.