Resisted External Rotation with Axial Pull is used to differentiate pathology between which structures, based on pain?

• A. Pn increases for subacromial bursa; decreases for Infraspinatus
• B. Pn unchanged for both
• C. Pn decreases = subacromial bursa; increases or stays the same = Infraspinatus RTC
• D. Pn decreases for subacromial bursa; increases for Infraspinatus RTC

Answer: (C)

This test differentiates pain sources in the shoulder by how the joint reacts to axial distraction while you resist external rotation. The axial pull tends to pull the humeral head away from the acromion, reducing contact in the subacromial space. If the pain is coming from the subacromial bursa, less contact means less irritation, so pain tends to decrease. If the pain comes from the infraspinatus tendon (rotator cuff), resisting external rotation actively loads and strains the tendon, so pain tends to increase or at least stay the same despite the distraction.

So, the pattern you look for is a reduction in pain with this test when the issue is subacromial bursitis, versus pain that increases or remains when the infraspinatus tendon is involved.