Shoulder pain with weak internal rotation is most consistent with weakness of which structure?

Shoulder pain with weak internal rotation is most consistent with weakness of which structure?

• A. Subscapularis
• B. Supraspinatus, deltoid
• C. Infraspinatus
• D. Teres minor

Answer: (A)

Internal rotation of the shoulder is mainly produced by the subscapularis. When this muscle is weak or torn, resisted internal rotation becomes noticeably weak and painful, which fits shoulder pain with internal rotation weakness. The other muscles listed are not internal rotators: the supraspinatus and deltoid are mainly involved in initiating and continuing arm abduction, while the infraspinatus and teres minor are external rotators. So the pattern points to subscapularis dysfunction as the best explanation. Tests like the lift-off or belly-press can help assess subscapularis strength if further evaluation is needed.

Internal rotation of the shoulder is mainly produced by the subscapularis. When this muscle is weak or torn, resisted internal rotation becomes noticeably weak and painful, which fits shoulder pain with internal rotation weakness. The other muscles listed are not internal rotators: the supraspinatus and deltoid are mainly involved in initiating and continuing arm abduction, while the infraspinatus and teres minor are external rotators. So the pattern points to subscapularis dysfunction as the best explanation. Tests like the lift-off or belly-press can help assess subscapularis strength if further evaluation is needed.