What physical examination finding is most suspicious for a tear of the supraspinatus in a patient with shoulder pain?

The correct answer is indicative of a tear in the supraspinatus due to the specific mechanics involved in shoulder motion and the functionality of the rotator cuff muscles. When there is a tear in the supraspinatus tendon, patients often experience a phenomenon known as "drop arm," which is characterized by a failure to smoothly control the lowering of the arm after it has been abducted. This occurs because the supraspinatus muscle is primarily responsible for initiating arm abduction and stabilizing the shoulder joint. When attempting to lower the arm from an abducted position, the loss of this stabilization and control becomes evident, leading to difficulty and a jerky motion rather than a smooth descent.

Understanding this mechanism helps clinicians assess the integrity of the rotator cuff during a physical examination. Other physical findings may suggest shoulder pathology as well, but the lack of smoothness in lowering the arm is particularly telling for a supraspinatus injury, making this finding highly suspicious for a tear. This specific characteristic distinguishes it from other potential problems, which may not demonstrate the same control issues.