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 cuff tears. However, its routine use is not advised, since it involves entering the joint with a needle with potential risk of infection. Consequently, the test is reserved for cases in which the diagnosis remains unclear. Musculoskeletal ultrasound has been advocated by experienced practitioners, avoiding the radiation of X-ray and the expense of MRI while demonstrating comparable accuracy to MRI for identifying and measuring the size of full-thickness and partial-thickness rotator cuff tears. This modality can also reveal the presence of other conditions that may mimic rotator cuff tear at clinical examination, including tendinosis, calcific tendinitis, subacromial subdeltoid bursitis, greater