Rotator cuff tear factors contribute to degenerative, or chronic, rotator cuff tears of which repetitive stress is the most significant. This stress consists of repeating the same shoulder motions frequently, such as overhead throwing, rowing, and weightlifting. Many jobs that require frequent shoulder movement such as lifting and overhead movements also contribute. Another factor in older populations is impairment of blood supply. With age, circulation to the rotator cuff tendons decreases, impairing natural ability to repair, ultimately leading to, or contributing to, tears. The final common factor is impingement syndrome, the most common non-sports related injury and which occurs when the tendons of
Synovial sheath 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 of narrow tendinous bands as threads known as vincula tendina. The synovial sheath is found where the tendon passes under ligaments and through osseofibrous tunnels; their