The radial nerve forms from the posterior cord of the brachial plexus, posterior to the second part of the axillary artery. It lies in the spiral groove on the posterior to the humerus with the profunda brachii artery, and runs medial to lateral.
Proximal to the elbow it pierces the intermuscular septum to lie in the anterior compartment where it runs distally deep to brachioradialis just lateral to the cubital fossa.
It divides into the superficial branch that continues distally, passing under the tendon of brachioradialis just before it inserts into the styloid process. This branch further divides near the anatomical snuff box (one of the smaller branches being palpable as it crosses extensor pollicis longus) to innervate skin over the dorsum of the hand and fingers.
The deep branch (the posterior interosseous nerve) runs on the posterior surface of the interosseous membrane. It does not pierce the membrane.
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