Inability to use the shoulder normally can follow a variety of athletic injuries, especially those involving the spinal cord, the brachial plexus, the acromioclavicular joint, the shoulder joint, the clavicle, and the sternoclavicular joint. Exact diagnosis is therefore essential for rational treatment. Understanding of the mechanics of injuries is also essential in designing protective equipment and planning operations to prevent recurrent dislocations. An unusual cause of pain is the displacement of the tendon of the long head of the biceps brachii from its normal location in the intertubercular groove of the humerus. Injuries to the shoulder are not limited to participants in contact sports. Valuable protection is afforded by special training and the use of protective equipment.