JERK TEST FOR POSTEROINFERIOR INSTABILITY Posterior instability often due to posteroinferior labrum tearscan be decently diagnosed with the help of the Jerk Test. Kim et al. (2004) found a sensitivity of 90% and a specificity of 85%, which makes it a moderate test to confirm posteroinferior labrum tears and a good test to exclude the pathology. The authors also describe that a painful response during this test was a predictor of failure for conservative treatment. | Physiotutors