What does the supraspinatus muscle initiate?

The supraspinatus muscle plays a critical role in shoulder movement by initiating the first 15 degrees of shoulder abduction. It is one of the rotator cuff muscles located at the posterior aspect of the shoulder. When the supraspinatus contracts, it helps to raise the arm away from the body, specifically starting the abduction movement, which is the action of lifting the arm laterally to the side.

At the beginning of abduction, the deltoid muscle, which is larger and more powerful, is not fully activated until the initial 15 degrees are completed. Therefore, the supraspinatus is essential for setting the motion into play, and without its action, complete abduction of the shoulder wouldn't be effectively achieved. Understanding this muscle's function is crucial in rehabilitation and treatment of shoulder injuries, as impairment of the supraspinatus often leads to difficulties in shoulder movement and can cause pain or dysfunction.