Purpose of Jerk Test: To test if there is a posteroinferior instability of the glenohumeral joint, indicating a torn posterior or posteroinferior labrum.

Patient position: Sitting with the affected arm supported on the patient’s lap over a pillow.

Examiner position: Standing behind the patient, near the affected shoulder.

Procedure: Stabilize the patient’s scapula using one hand and hold the patient’s elbow with another hand. Elevate the patient’s arm up to 90-degree abduction and internal rotation. Grasp the patient’s elbow and axially load the humerus towards the glenoid cavity with slight adduction of the arm (1). Move the arm into horizontal adduction while maintaining the axial compression force (2).

Outcome: A sudden jerk or clunk as the humeral head suddenly subluxes or reduces over the posterior glenoid rim along with or without an abrupt pain indicates a positive test (3). Another jerk or clunk may be observed as the examiner returns the humeral head to the original position (4).

Reference:

1. Imhoff AB, Ticker JB, Mazzocca AD, Voss A. Atlas of Advanced Shoulder Arthroscopy: CRC Press; 2017.
2. Magee DJ. Orthopedic Physical Assessment: Elsevier Health Sciences; 2013.
3. Kim SH, Park JC, Park JS, Oh I. Painful jerk test: a predictor of success in nonoperative treatment of posteroinferior instability of the shoulder. The American journal of sports medicine. 2004;32(8):1849-55.
4. Rockwood CA. The Shoulder: Saunders/Elsevier; 2009.