The Posterior interosseous nerve (PIN) arises from the radial nerve; the radial nerve (RN) divides into a sensory branch and a deep motor branch, which pierces the supinator muscle. Trauma, tumours, compression or inflammation can cause lesions of the RN.

Symptoms such as ulnar wrist drop and finger drop are clinical manifestations of a PIN lesion. Elbow extension, complete wrist drop and supination weakness are symptoms related to a RN lesion. Neuroimaging and magnetic resonance neurography (MRN) can be used to diagnose these lesions.