Which muscle's function is primarily tested by the empty can test?

Which muscle's function is primarily tested by the empty can test?

• A. Deltoid.
• B. Supraspinatus.
• C. Infraspinatus.
• D. Subscapularis.

Answer: (B)

This test targets the supraspinatus, a rotator cuff muscle that initiates arm abduction and helps stabilize the humeral head. Positioning the arm in the scapular plane with about 90 degrees of abduction and internal rotation (thumbs pointing down) biases the supraspinatus to work against downward resistance. If the patient shows weakness or pain when resisting, it suggests supraspinatus pathology such as tendinopathy or a tear. The deltoid’s contribution is minimized in this position, so it more specifically tests the supraspinatus. Other rotator cuff muscles are tested with different maneuvers: the infraspinatus with resisted external rotation, and the subscapularis with internal rotation against resistance or a lift-off test.

This test targets the supraspinatus, a rotator cuff muscle that initiates arm abduction and helps stabilize the humeral head. Positioning the arm in the scapular plane with about 90 degrees of abduction and internal rotation (thumbs pointing down) biases the supraspinatus to work against downward resistance. If the patient shows weakness or pain when resisting, it suggests supraspinatus pathology such as tendinopathy or a tear. The deltoid’s contribution is minimized in this position, so it more specifically tests the supraspinatus. Other rotator cuff muscles are tested with different maneuvers: the infraspinatus with resisted external rotation, and the subscapularis with internal rotation against resistance or a lift-off test.