The radial nerve is the largest branch of the brachial plexus, and is commo
nly involved in upper extremity mononeuropathies. The radial nerve is prima
rily responsible for motor innervation of the upper extremity extensors, as
well as receiving cutaneous innervation from most of the posterior arm, fo
rearm, and hand. There are a variety of sites at which the radial nerve is
susceptible to trauma and entrapment. Localizing radial nerve lesions is de
pendent on clinical knowledge of radial nerve anatomy, and sensory and moto
r examination.