Rotator cuff tear rotator cuff tear. Generally, the incidence of rotator cuff tears or injuries increases by age while corticosteroid injection for pain relief increases the risk of tendon tear and delays tendon healing. The shoulder is a complex mechanism involving bones, ligaments, joints, muscles, and tendons. The two main causes are injury (acute) and degeneration (chronic and cumulative), and the mechanisms involved can be either extrinsic or intrinsic or, probably most commonly, a combination of both. The cuff is responsible for stabilizing the glenohumeral joint, abducting, externally rotating, and internally rotating the humerus. When shoulder trauma occurs, these functions can be compromised.
Rotator cuff arm, moving it outward and away from the trunk, the rotator cuff compresses the glenohumeral joint, an action known as concavity compression, in order to allow the large deltoid muscle to further elevate the arm. In other words, without the rotator cuff, the humeral head would ride up partially out of the glenoid fossa, lessening the efficiency of the deltoid muscle. The anterior and posterior directions of the glenoid fossa are more susceptible to shear force perturbations as the glenoid fossa is not as deep relative to the superior and inferior directions. The rotator cuff's contributions to concavity compression and