The radial nerve runs all the way down the arm. It controls movement of the triceps muscle and wrist extension. In addition, it assists with sensation in the hand and wrist. The triceps are located on the back of the arms. Any problems with hand, wrist, or triceps movement and any arm sensation problems may be indicative of possible radial nerve dysfunction. This might result from prolonged nerve pressure, nerve compression, or direct trauma. Examples of possible causes include consistently wearing a tight fitting watch, sustaining a humerus fracture, sleeping in positions that put pressure on the upper arm, or using crutches improperly. If the damage only affects one nerve group, like the radial nerve, it is called mono-neuropathy. The radial nerve passes through the humerus spiral groove and the arch formed by the attachment of the humerus and triceps. It also passes through the lateral intermuscular septum and the Arcade of Frohse. This is located below the elbow but above the supinator.