Architectural gear ratio and their accompanying tendons. These muscles form a cuff around the glenohumeral joint and function to stabilize and manipulate the shoulder. The pennation angle of the rotator cuff myofibers, the angle at which fibers connect to the associated tendon, affects the contractile properties and function of the whole pennate muscle. For example, the pennation angle determines the architectural gear ratio at which a pennate muscle operates. A large initial pennation angle results in a large AGR and velocity amplification. A 2011 study on human cadaveric shoulders suggests tendon tears may affect the pennation angle of the rotator cuff muscles. Researchers
Rotator cuff tear or arthritis. Superior labral anterior-posterior lesions produce pain similar to that of rotator cuff tears. Those most prone to failed rotator cuff syndrome are patients 65 years of age or older; and those with large, sustained tears. Smokers, diabetes sufferers, patients with muscle atrophy and/or fatty infiltration, and those who do not follow postoperative-care recommendations also are at greater risk. Doctors examine patients and conduct imaging tests to identify the causes of continued discomfort. Depending upon the diagnosis, several treatment alternatives are available. They include revision repair, nonanatomic repair, tendon transfer and arthroplasty. When possible, surgeons make tension-free repairs in