The rotator cuff is the name used for the attachment of the humerus to the scapula at the glenohumeral joint of the shoulder. This joint is a ball-and-socket-type joint that is inherently unstable due to the relatively shallow socket of the glenoid fossa. The rotator cuff provides stability to the shoulder through four muscles: the supraspinatus, infraspinatus, teres minor and subscapularis. These four muscles surround the glenohumeral joint and provide stability and flexibility to the shoulder as well as assist in some of the motions of this joint.
Supraspinatus Muscle
The supraspinatus muscle originates in the depression above the spine of the scapula, called the supraspinous fossa, and inserts onto the humerus at the greater tubercle. This muscle forms the upper portion of the rotator cuff and assists in lifting the arm at the shoulder joint.
Infraspinatus Muscle
The infraspinatus muscle originates below the spine of the scapula and inserts onto the humerus at the greater tubercle. This muscle forms the back side of the rotator cuff and serves to turn the arm toward the back at the shoulder as well as providing stability to this joint.
Teres Minor Muscle
The teres minor muscle originates on the lower side of the scapula and inserts onto the humerus at the greater tubercle. This muscle forms the lower back side and base of the rotator cuff, providing stability and assisting in pulling the arm downward and turning the arm toward the back at the shoulder.
Subscapularis Muscle
The subscapularis muscle originates on the underside of the scapula (between the scapula and the ribs) and inserts onto the lesser tubercle of the humerus. It forms the front side of the rotator cuff and serves to rotate the arm forward at the shoulder and provide stability for the genohumeral joint.
References
- "Gray's Anatomy: The Anatomical Basis of Clinical Practice"; Susan Standring (Editor); 2008
- "Trail guide to the body: how to locate muscles, bones and more"; Andrew Biel; 2005
