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 extension, or vertical abduction, it is less likely to suffer from a tear of the tendon. Those suspected of having a rotator cuff tear may have operative or non-operative treatment. No evidence of benefit is seen from early rather than delayed surgery, and many with partial tears and some with complete tears will respond to nonoperative management. Consequently, many recommend initial, nonsurgical management. However, early surgical treatment may be considered in significant (>1 cm-1.5 cm) acute tears or in young patients with full-thickness tears who have a significant risk for the development of irreparable rotator cuff changes. A review in