By Chris Faubel, MD –
The posterior interosseous nerve (PIN) is one of those nerves learned best by knowing the exceptions.
Source: Clinically Oriented Anatomy, 4th edition
In this case, the PIN innervates all the muscles on the dorsal side of the forearm, EXCEPT the brachioradialis, extensor carpi radialis longus (ECRL), and anconeus.
- It may help to remember these 3 exceptions by remembering they are the only muscles in the dorsal forearm that cross the elbow joint
- So that means, ALL dorsal forearm muscles that do NOT cross the elbow joint are innervated by the deep radial nerve/PIN (see below)
When does the radial nerve become the PIN?
