The Arm

The arm is that part of the upper extremity between the shoulder and the elbow. Important proximal muscles acting on the shoulder and elbow joint are present, along with terminal branch nerves of the brachial plexus. The muscle compartments are easily divided into flexor and extensor groups. Knowledge of these structures and muscle groups is important for the assessment of local pathology and also for tracing pathology proximal and distal to the more commonly imaged shoulder and elbow joints.