In the infraspinatus test, how is the arm positioned?

In the infraspinatus test, the arm is positioned by the side with the elbow flexed at 90 degrees. This positioning is crucial for isolating the infraspinatus muscle, which is one of the rotator cuff muscles primarily responsible for external rotation of the shoulder. When the arm is positioned this way, it allows the clinician to effectively assess the function and strength of the infraspinatus without the influence of other muscles or compensatory movements.

Holding the arm at the side with a flexed elbow minimizes the involvement of the other rotator cuff muscles and focuses tension directly on the infraspinatus. During the test, resistance is applied while the patient attempts to externally rotate the arm, which provides insight into the integrity and strength of the infraspinatus muscle. This method is standardized in clinical practice, aiding in diagnosing potential rotator cuff pathology or shoulder instability.

The other positioning options would either not isolate the infraspinatus effectively or engage other muscle groups, which could lead to misleading results or interpretations regarding the strength and function specifically of the infraspinatus.