Deep Branch of the Radial Nerve, Lateral View

Description

Arising from the radial nerve on the lateral side of the elbow, the deep branch courses anterior to the lateral epicondyle and then passes between the superficial and deep layers of the supinator, where it begins its transition toward the posterior compartment as the posterior interosseous nerve. Proximally, it lies deep to brachioradialis and extensor carpi radialis longus and brevis, with its fascicles running close to the radial head and the proximal radius. Distally, the nerve tracks along the posterior aspect of the interosseous membrane, sending motor branches to the extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, and the thumb extensors and abductors. No sensory cutaneous branch accompanies it. This is the motor side of the radial nerve. A lateral perspective makes the nerve’s relationship to the supinator and the arcade of Frohse easy to teach. That fibrous proximal edge of the supinator is the most common site of posterior interosseous nerve entrapment, producing finger and thumb extension weakness with preserved wrist extension and no cutaneous numbness, a pattern that helps distinguish it from a more proximal radial neuropathy in the spiral groove. Surgeons planning approaches to the radial head, proximal radius, or lateral elbow also track this pathway closely because retraction and hardware can injure the nerve as it disappears into the extensor compartment. Clean anatomy, real consequences. Use this illustration to support upper-limb anatomy labs, peripheral nerve modules, and orthopaedic or hand surgery teaching on radial tunnel syndrome and posterior interosseous nerve palsy, as well as figure plates for clinical textbooks describing lateral elbow approaches and extensor compartment innervation. Anatomical accuracy verified by SciePro's Medical Advisory Board.