Teres major muscle

The teres major is a thick, flattened, somewhat fusiform-shaped shoulder muscle that extends between the scapula and the humerus. It lies posterior to the scapula and inferior to the teres minor and infraspinatus. It works synergistically with the latissimus dorsi muscle to adduct, extend, and medially rotate the arm. This muscle also stabilizes the head of the humerus within the glenoid cavity during arm movements, preventing subluxation together with the rotator cuff muscles. It is important to note that the teres major is not classified as a rotator cuff muscle.