Which substitution is most likely when testing external rotation at the shoulder?

Which substitution is most likely when testing external rotation at the shoulder?

• A. Trunk rotation
• B. Scapular elevation
• C. Elbow movement that reduces rotation
• D. Neck rotation

Answer: (C)

Substitution happens when other joints compensate, so the movement you’re trying to isolate at the shoulder comes partly from somewhere else. For external rotation of the shoulder, the elbow is a common source of that compensation. If the elbow moves, the forearm can take on part of the rotation burden, effectively changing the lever and reducing how much rotation the glenohumeral joint has to produce. This makes the test show less rotation than is truly possible at the shoulder, which is why elbow movement that reduces rotation is the most likely substitution pattern. Other compensations like trunk, neck, or scapular adjustments can occur, but they’re less directly tied to the specific rotation being tested.

Substitution happens when other joints compensate, so the movement you’re trying to isolate at the shoulder comes partly from somewhere else. For external rotation of the shoulder, the elbow is a common source of that compensation. If the elbow moves, the forearm can take on part of the rotation burden, effectively changing the lever and reducing how much rotation the glenohumeral joint has to produce. This makes the test show less rotation than is truly possible at the shoulder, which is why elbow movement that reduces rotation is the most likely substitution pattern. Other compensations like trunk, neck, or scapular adjustments can occur, but they’re less directly tied to the specific rotation being tested.