Shoulder pain with weak external rotation is most consistent with weakness of which muscles?

Shoulder pain with weak external rotation is most consistent with weakness of which muscles?

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

Answer: (A)

External rotation of the shoulder is produced mainly by the infraspinatus and teres minor. When a patient has pain with and weakness in external rotation, the most likely problem is weakness of these external rotators. The subscapularis is an internal rotator, so weakness there would predominantly affect internal rotation rather than external rotation. Supraspinatus and deltoid are mainly involved in initiating and sustaining abduction, not external rotation, so their weakness wouldn’t explain a primary external rotation deficit. Teres minor contributes to external rotation but is a smaller muscle; the classic pattern is weakness of the primary external rotators, infraspinatus and teres minor, leading to reduced external rotation strength.

External rotation of the shoulder is produced mainly by the infraspinatus and teres minor. When a patient has pain with and weakness in external rotation, the most likely problem is weakness of these external rotators. The subscapularis is an internal rotator, so weakness there would predominantly affect internal rotation rather than external rotation. Supraspinatus and deltoid are mainly involved in initiating and sustaining abduction, not external rotation, so their weakness wouldn’t explain a primary external rotation deficit. Teres minor contributes to external rotation but is a smaller muscle; the classic pattern is weakness of the primary external rotators, infraspinatus and teres minor, leading to reduced external rotation strength.