Which dysfunction does weakness or pain during the full can test most likely indicate?

Which dysfunction does weakness or pain during the full can test most likely indicate?

• A. Supraspinatus dysfunction
• B. Infraspinatus dysfunction
• C. Subscapularis tendonitis
• D. Glenoid labrum tear

Answer: (A)

The main idea tested is the function of the supraspinatus muscle during resisted abduction in the scapular plane. In the full can position, the arm is elevated about 90 degrees in the scapular plane with the thumb pointing downward, and the patient resists upward pressure. This setup places the supraspinatus under load while minimizing deltoid over-activity, so weakness or pain in this maneuver points to supraspinatus tendon pathology—such as tendinopathy or a tear, or impingement related to the supraspinatus. The other options don’t fit this test as precisely: weakness with resisted external rotation would implicate the infraspinatus; tests that focus on internal rotation or lifting the hand off the back target the subscapularis; a glenoid labrum tear is best inferred from tests that stress the labrum and reproduce joint line pain or instability rather than this specific abduction maneuver.

The main idea tested is the function of the supraspinatus muscle during resisted abduction in the scapular plane. In the full can position, the arm is elevated about 90 degrees in the scapular plane with the thumb pointing downward, and the patient resists upward pressure. This setup places the supraspinatus under load while minimizing deltoid over-activity, so weakness or pain in this maneuver points to supraspinatus tendon pathology—such as tendinopathy or a tear, or impingement related to the supraspinatus.

The other options don’t fit this test as precisely: weakness with resisted external rotation would implicate the infraspinatus; tests that focus on internal rotation or lifting the hand off the back target the subscapularis; a glenoid labrum tear is best inferred from tests that stress the labrum and reproduce joint line pain or instability rather than this specific abduction maneuver.