The empty can test isolates weakness or tears of which muscle?

The empty can test isolates weakness or tears of which muscle?

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

Answer: (B)

The key idea is that this test targets the supraspinatus tendon. Placing the arm in about 90 degrees of forward elevation in the scapular plane with internal rotation (thumb pointing down) and asking the patient to resist downward pressure makes the deltoid’s contribution to abduction minimal. In this position, the supraspinatus from the top of the shoulder is the primary muscle driving the initial upward force. If the supraspinatus tendon is torn or diseased, the patient will show weakness or reproduce pain when resisting, indicating supraspinatus pathology. Other rotator cuff muscles aren’t the main players in this maneuver: weakness with resisted external rotation points to the infraspinatus, while subscapularis weakness is evaluated with different internal rotation tests (like lift-off or bear-hug). The deltoid’s strength is tested more effectively in other arm positions where it can act without being overwhelmed by the supraspinatus.

The key idea is that this test targets the supraspinatus tendon. Placing the arm in about 90 degrees of forward elevation in the scapular plane with internal rotation (thumb pointing down) and asking the patient to resist downward pressure makes the deltoid’s contribution to abduction minimal. In this position, the supraspinatus from the top of the shoulder is the primary muscle driving the initial upward force. If the supraspinatus tendon is torn or diseased, the patient will show weakness or reproduce pain when resisting, indicating supraspinatus pathology.

Other rotator cuff muscles aren’t the main players in this maneuver: weakness with resisted external rotation points to the infraspinatus, while subscapularis weakness is evaluated with different internal rotation tests (like lift-off or bear-hug). The deltoid’s strength is tested more effectively in other arm positions where it can act without being overwhelmed by the supraspinatus.