The radial nerve is one of the two terminal branches of the posterior cord. It supplies the muscles in the posterior arm and forearm. The superficial radial nerve supplies the skin of the dorsal aspect of the lateral three-and-a-half fingers and the anatomical snuff box. The radial nerve is commonly injured with fractures of the mid-shaft of the humerus and causes wrist drop. The posterior interosseous nerve (PIN) can be entrapped under the sharp edge of the supinator (arcade of Fröhse) or involved in cases of brachial plexitis (Parsonage–Turner syndrome). It causes finger drop and weak wrist extension with radial deviation.