Radial Nerve Injuries: Posterior Interosseous Nerve Syndrome

After emerging from under the supinator, the radial nerve may be compressed before it bifurcates into medial and lateral branches. This can cause a complete paralysis of wrist extension.

If compression occurs after the nerve bifurcates the patient will complain of weakness of the wrist and finger extensors.

Attempts at active wrist extension result in weak dorsoradial deviation because extensor carpi radialis is supplied by the radial nerve proximal to the bifurcation.

The image illustrates the route of the radial nerve in the elbow.