Extensor Pollicis Brevis Muscle as, Posterior View

Description

Running along the dorsolateral distal forearm, the extensor pollicis brevis (EPB) is isolated in red as it transitions from a muscular belly to a tendon that passes distally toward the radial side of the wrist and into the thumb. From this posterior perspective, the radius lies lateral to the ulna, and the EPB course stays close to the distal radius before approaching the base of the first metacarpal and proximal phalanx region. Carpal bones, metacarpals, and phalanges provide the bony framework for the wrist and thumb column. Orientation is clear. Because EPB shares the first dorsal extensor compartment with abductor pollicis longus, this posterior-dorsolateral view maps directly onto the anatomy examined in de Quervain tenosynovitis, where thickening of the compartment retinaculum produces pain at the radial styloid with thumb extension and abduction. The illustration also helps distinguish EPB from extensor pollicis longus, whose tendon takes a more medial course around Lister’s tubercle in the third compartment, a relationship surgeons use when planning dorsal wrist approaches and when teaching tendon compartment injections. Variants matter, including an absent EPB or a separate EPB subsheath, both relevant to persistent symptoms after release. Use this artwork in upper limb anatomy teaching (forearm extensor compartments and thumb biomechanics), in hand surgery atlases describing first dorsal compartment release, and in radiology or sports medicine materials that correlate ultrasound probe position with the radial styloid and extensor retinaculum. It also suits patient-facing education on radial-sided wrist pain when paired with Finkelstein or Eichhoff test explanations. Anatomical accuracy verified by SciePro's Medical Advisory Board.