Deep Branch of the Radial Nerve, Posterior View

Description

Arising from the radial nerve in the distal arm, the deep branch courses posterior to the lateral epicondyle and enters the supinator on the lateral side of the proximal forearm, where it turns anterior to posterior around the proximal radius. In a posterior perspective, the nerve lies deep to brachioradialis and extensor carpi radialis longus and brevis, then tracks between the superficial extensor compartment and the deeper extensor mass. After traversing the supinator (Arcade of Frohse region), it continues distally as the posterior interosseous nerve, running on the posterior interosseous membrane with segmental branches to extensor digitorum, extensor carpi ulnaris, extensor pollicis longus and brevis, abductor pollicis longus, and extensor indicis. No cutaneous branch. That transition from deep branch to posterior interosseous nerve is the teaching point surgeons and clinicians look for, because it marks a common entrapment site in radial tunnel syndrome and posterior interosseous nerve palsy. Compression at the fibrous edge of the supinator can produce motor weakness in finger and thumb extension with relative preservation of wrist extension (extensor carpi radialis longus often spared), a pattern that helps distinguish it from a more proximal radial neuropathy in the spiral groove. It is also a landmark during lateral elbow approaches and supinator-splitting exposures for proximal radius fixation. Use this asset for upper limb anatomy labs, peripheral nerve modules, and orthopedic or hand surgery atlases that need a clean posterior map of the deep radial nerve as it dives into the supinator and emerges as the posterior interosseous nerve. It also supports exam-prep diagrams for localizing radial neuropathies around the elbow. Anatomical accuracy verified by SciePro's Medical Advisory Board.