Shoulder Orthopaedic Test: Jerk Test

The Jerk test is a physical examination maneuver used to detect posteroinferior instability of the glenohumeral joint. This test involves a sudden and forceful posteriorly directed force applied to the patient's arm while it is held in a position of abduction and external rotation.

Here is a step-by-step procedure for performing the Jerk test:

1. Ask the patient to sit or stand with their arm at their side.
2. Grasp the patient's forearm with one hand and the upper arm with the other hand.
3. Passively abduct the patient's arm to 90 degrees and externally rotate it to the point of pain or apprehension.
4. Apply a sudden and forceful posteriorly directed force to the patient's arm.
5. Observe the patient's response to the maneuver, looking for a sudden jerk or clunk sensation as the humeral head subluxates posteriorly and then relocates back into the glenoid fossa.

If a sudden jerk or clunk sensation is felt during the Jerk test, it may suggest posteroinferior instability of the glenohumeral joint.

References:

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2. Jobe FW, Giangarra CE, Kvitne RS. Shoulder pain in the overhand or throwing athlete: the relationship of anterior instability and rotator cuff impingement. Orthop Rev. 1986;15(6):361-367.
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