Muscles of the Shoulder:
Shoulder Muscles - Sports Injury InfoNext in shoulder anatomy is the muscles. Shoulder stability is highly dependent upon the muscles of the shoulder, specifically the rotator cuff muscles.
The rotator cuff is comprised of four seperate muscles, all originating from the scapula and inserting on the humeral head. The rotator cuff muscles can be classified by their positions on the body. The posterior rotator cuff includes two muscles on the back of the shoulder. The infraspinatus and the teres minor. These muscles are responsible for external rotation of the humerus.
The superior rotator cuff is found on top of the shoulder, and includes the supraspinatus. This muscle is commonly injured with a rotator cuff tear.
Shoulder Muscles - Sports Injury InfoThe third and final group of rotator cuff muscles is the anterior rotator cuff, which includes the subscapularis. This muscles sits on the front of the shoulder, and causes internal rotation of the humerus.
Together, the rotator cuff muscles help to keep the humerus centered in the glenoid fossa, and to provide stability to the shoulder joint during activity.
Other muscles that play an important role in shoulder stability include the scapular stabilizers. This group of muscles originate from the spine, and run to the scapula.
The primary scapular stabilizers are the rhomboids and trapezius. In addition to the rotator cuff and scapular stabilizers, the deltoid is another important shoulder muscles, found on the outside of the upper arm.