Teres minor is a small, rounded rotator cuff muscle. It is the smallest of the four. It attaches from the rear, outer edge of the shoulder blade to the head of the humerus. Most importantly, in conjunction with the other rotator cuff muscles, it is responsible for dynamic stabilization of the shoulder joint, especially during upward movement of your arm.
The shoulder has less connective tissue structure than other major joints. The rotator cuff muscles, including teres minor, act as a sort of dynamic muscle/ligament hybrid to stabilize your shoulder joint as you move.
The other important function of teres minor is to provide externally rotate your arm.
Trigger points in your teres minor refer pain deep in the back part of the deltoid area and can extend down your arm.
Teres minor trigger points are activated by overload reaching backward or upward. Corrective actions include behavior change to reduce overload, self-pressure release and stretching exercises.