External Rotation Lag Sign is used to test the integrity of the supraspinatus and infraspinatus tendons.
How it's Performed?
The patient is seated with his or her back to the examiner.
The elbow is passively flexed to 90 degrees, and the shoulder is held at 20° of elevation and near maximal external rotation (maximal external rotation minus 5 degrees to avoid elastic recoil in the shoulder) by the examiner.
The patient is asked to maintain the position of external rotation actively as the examiner releases the wrist, while maintaining support of the arm at the elbow.
The same test can be repeated with the arm abducted to 90°, which specifically tests the infraspinatus and teres minor muscles.
What does a positive External Rotation Lag Sign mean?
External Rotation Lag Sign is positive when a lag, or angular drop, occurs.
If the patient cannot hold the arm in the position into which it was passively placed (submaximal external rotation with slight abduction) and it reverts to the internally rotated position, then this indicates a lesion of the supraspinatus tendon.
If the position cannot be held at 90° abduction, the test is highly sensitive and specific for a lesion of the teres minor muscle.