The infrapinatus muscle is a thick irregular rotator cuff muscle located on the back of your shoulder blade. It has a strong connection to the shoulder and along with teres minor, rotates your arm externally. 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 infraspinatus, act as a sort of dynamic muscle/ligament hybrid to stabilize the shoulder joint as you move.

Of the important functions of infraspinatus is to provide force to seat the head of humerus when you extend your arm up.

Trigger points in your infraspinatus refer pain deep in the front part of the deltoids, and sometimes extending down the side of your arm past the elbow to the top and thumb side of your forearm and hand. Infraspinatus can also cause pain on the inside edge of your shoulder blade.

Infraspinatus trigger points are often involved with shoulder impingement syndromes and subacromial pain syndrome. Trigger point referrals from infraspinatus can initiate central sensitization leading to chronic shoulder pain.