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.
Synovial sheath function is to reduce friction between the tendon and their surrounding structure. An example is the common synovial sheath for the flexor tendons of the hand. Synovial sheath A synovial sheath is one of the two membranes of a tendon sheath which covers a tendon. The other membrane is the outer fibrous tendon sheath. The tendon invaginates the synovial sheath from one side so that the tendon is suspended from the membrane by the mesotendon, through which the blood vessels reach the tendon, in places where the range of movement is extensive. The mesotendon disappears or remains in the form