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Jerk Test for posterior shoulder subluxation

The Jerk Test  is used to detect postero-inferior instability of the Glenohumeral joint.

  • To perform the jerk test, the patient sits with the arm medially rotated and forward flexed to 90°.
  • The therapist grasps the patient’s elbow and axially loads the humerus in a proximal direction.
  • Along with the axial loading, the examiner moves the arm horizontally (crossflexion/ horizontal adduction) across the body.
  • A positive test for recurrent posterior instability is the production of a sudden jerk or clunk as the humeral head slides off (subluxes) the back of the glenoid.
  • When the arm is returned to the original 90° abduction position, a second jerk may be felt as the head reduces.