Three isometric tests are used to evaluate the strength of the different components of the cuff. The supraspinatus is challenged by isometric flexion of the internally rotated arm, which is elevated 90 degrees in the plane of the scapula. The infraspinatus is challenged by isometric external rotation with the arm in neutral rotation at the side. The subscapularis is challenged by isometric internal rotation, pushing the hand away from the waist in the posterior midline. The size of the cuff tear can be estimated by physical examination.
Partial tears tend to demonstrate relatively more pain with minimal loss of strength.
Small tears usually compromise only the function of the supraspinatus. Large tears involve the infraspinatus and compromise external rotation. Massive tears compromise the subscapularis and weaken internal rotation. Shoulders with incomplete thickness cuff lesions often manifest limitation of motion, particularly in flexion, internal rotation, and cross-body movement due to selective tightness of the posterior capsule. The examination of a patient with a weak shoulder must include the neck and brachial plexus.