This mechanical shoulder simulator study asks whether the 5° difference in critical shoulder angle (CSA) that separates normal shoulders from those with rotator cuff tears — 33° vs. 38° — is enough to biomechanically overload the supraspinatus tendon during routine arm abduction.
When you measure a CSA ≥38° on an AP shoulder radiograph, recognize that this morphology mechanically obligates the supraspinatus to work 13–34% harder just to stabilize the joint during low-arc abduction — the biomechanical substrate for why large-CSA shoulders are predisposed to supraspinatus tears independent of activity level or occupation.
This mechanical shoulder simulator study asks whether the 5° difference in critical shoulder angle (CSA) that separates normal shoulders from those with rotator cuff tears — 33° vs. 38° — is enough to biomechanically overload the supraspinatus tendon during routine arm abduction.
When you measure a CSA ≥38° on an AP shoulder radiograph, recognize that this morphology mechanically obligates the supraspinatus to work 13–34% harder just to stabilize the joint during low-arc abduction — the biomechanical substrate for why large-CSA shoulders are predisposed to supraspinatus tears independent of activity level or occupation.