Which muscle is indicated by weakness or pain in the full can test?

Which muscle is indicated by weakness or pain in the full can test?

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

Answer: (B)

The full can test targets the supraspinatus muscle. Positioning the arm in the scapular plane with about 90 degrees of abduction and the arm in a position of maximal external rotation places the supraspinatus under load as the patient resists downward pressure. If weakness or pain is present, it points to supraspinatus tendinopathy or tear, which is a common rotator cuff issue affecting this muscle’s ability to initiate arm abduction and stabilize the humeral head. The other muscles mentioned produce weakness or pain in different tests. The infraspinatus and teres minor are external rotators, so weakness shows up with resisted external rotation rather than in the full can position. The subscapularis is an internal rotator; its pathology is better revealed by tests like the belly press or lift-off. Thus, the full can test most specifically implicates the supraspinatus.

The full can test targets the supraspinatus muscle. Positioning the arm in the scapular plane with about 90 degrees of abduction and the arm in a position of maximal external rotation places the supraspinatus under load as the patient resists downward pressure. If weakness or pain is present, it points to supraspinatus tendinopathy or tear, which is a common rotator cuff issue affecting this muscle’s ability to initiate arm abduction and stabilize the humeral head.

The other muscles mentioned produce weakness or pain in different tests. The infraspinatus and teres minor are external rotators, so weakness shows up with resisted external rotation rather than in the full can position. The subscapularis is an internal rotator; its pathology is better revealed by tests like the belly press or lift-off. Thus, the full can test most specifically implicates the supraspinatus.