A 19-year-old man is brought to the emergency department after dislocating his shoulder while playing soccer. Following reduction of the dislocation, he has pain over the dorsal region of the shoulder and cannot abduct the arm normally. An MRI of the shoulder shows a torn muscle. Which of the following muscles is most likely to have been damaged by this injury?

The supraspinatus is one of the rotator cuff muscles. Its tendon is relatively avascular and is often injured when the shoulder is dislocated. This muscle initiates abduction of the arm, and damage would impair this movement. The coracobrachialis muscle, which runs from the coracoid process to the humerus, functions in adduction and flexion of the arm. The triceps' main function is to extend the elbow, and damage to its long head would not affect abduction. The pectoralis minor functions as an accessory respiratory muscle and to stabilize the scapula and is not involved in abduction. The teres major functions to adduct and medially rotate the arm.