Tendon Sheath of the Extensor Carpi Radialis Brevis, Posterior View

Description

Running along the dorsoradial forearm, the extensor carpi radialis brevis (ECRB) muscle belly tapers into its tendon as it courses distally toward the base of the third metacarpal, lying deep to extensor carpi radialis longus and lateral to extensor digitorum. A synovial tendon sheath surrounds the ECRB tendon as it passes beneath the extensor retinaculum at the dorsal wrist, with the retinacular bands forming a fibrous roof over the extensor compartments. Blue-tinted retinaculum and synovial covering contrast with the pale tendons and red muscle bellies, clarifying the layered anatomy from superficial to deep in a posterior (dorsal) view. Orientation is dorsal hand, palm down. This posterior perspective is the one you want when teaching why extensor tendons do not bowstring during wrist extension and why tenosynovitis presents as pain and crepitus during active motion. The ECRB tendon’s passage under the extensor retinaculum links directly to intersection syndrome, where friction and synovial irritation occur at the dorsoradial wrist as the first dorsal compartment tendons cross the ECRL/ECRB region. Small space, predictable symptoms. Use it in upper-limb anatomy lab manuals, hand therapy education focused on dorsal wrist compartments and retinacular mechanics, or as a figure in orthopedic and sports medicine content discussing dorsal wrist pain and extensor tendon sheath inflammation. Anatomical accuracy verified by SciePro's Medical Advisory Board.