The infraspinatous muscle is one of the four muscles of the rotator cuff in addition to the supraspinatus, teres minor, and subscapularis. It is a triangular shoulder muscle that rises above and is attached to the infraspinatous fossa, which is also known as the shoulder blade. This muscle helps to achieve lateral motion and horizontal extension of the arm as well as overall joint stability. This thin shoulder muscle is attached to the suprascapular nerve and is therefore associated with the C5 and C6 vertebrae. Two thirds of this muscle is composed of fleshy fibers, while the other third is devoted to tendinous fibers that become the infraspinatous tendon. The infraspinatous muscle is the second most injured muscle of the shoulder. Motions required to throw a ball or swing a racket can cause strain within the muscle and referred pain throughout the shoulder area. Combined with stress from the infraspinatous tendon, chronic pain in this area may be diagnosed as infraspinatous tendinitis.
Written and medically reviewed by the Healthline Editorial Team
In Depth: Infraspinatus