Jerk test is a shoulder examination used to determine posteroinferior instability.
- Patient seated, examiner flexes patient’s arm to 90° & internally rotates glenohumeral joint, while applying long axis compression on the humerus.
- Examiner then proceeds to horizontally adduct the shoulder across the front of the patient’s body while maintaining the long axis compressive force.
Positive Sudden jerk, clunk or patient apprehension as the arm is moved → Posterior glenohumeral instability.
“Clunk” occurs as the humeral head slides posteriorly over the glenoid labrum (orthopedic glenohumeral subluxation), as the arm is returned to its original position the second clunk may be noted as the humeral head reduces.