Deep branch of radial nerve

The deep branch of the radial nerve originates from the radial nerve in the cubital fossa, where the radial nerve bifurcates into the superficial branch (sensory) and the deep branch (motor). The deep branch of the radial nerve then travels posteriorly, entering the supinator muscle through the arcade of Frohse, which is the tendinous superior border of the supinator muscle.

After passing through the supinator, the deep branch of the radial nerve continues as the posterior interosseous nerve of forearm, innervating the extensor muscles of the forearm, including the extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, and the extensor indicis. (all the muscles on the radial side and dorsal surface of the forearm, excepting the Anconæus, Brachioradialis, and Extenosr carpi radialis longus).