Jerk Test is used to check for posterior instability of the shoulder joint (It’s used to detect a posteroinferior labral lesion).
How do you perform the Jerk Test?
The patient stands or sits. The examiner abducts the affected arm 90° at the shoulder with the elbow flexed 90°.
The examiner’s other hand stabilizes the shoulder girdle from behind.
From this position, the examiner attempts to provoke a posterior drawer sign (subluxation) using increasing internal rotation and adduction with simultaneous axial pressure.
What does a positive jerk test mean?
If posterior instability is present, the posteriorly oriented thrust along the longitudinal axis of the humerus with slowly increasing adduction leads to posterior subluxation in the glenohumeral joint.
Abducting the arm horizontally by 20 to 30° in the same horizontal plane will lead to palpable “snapping” reduction of the humeral head back into the socket with a “jerk” or a “clunk” (Positive Jerk Test).
Sensitivity & Specificity
A comparison study by Seung-Ho Kim 2 on 172 painful shoulders, the Kim test was compared with the jerk test and was verified by arthroscopic examination, the accuracy of jerk test was as following:
Sensitivity: 73 %
Kim test is a novel diagnostic test that is used to detect a posteroinferior labral lesion of the shoulder joint. It’s a modification of jerk test.
This test is done with the patient sitting, and the clinician standing on the involved side. The clinician grasps the elbow with one hand and the mid humeral region with the other hand, then elevates the patient’s arm to 90 degrees of abduction. Simultaneously, the clinician provides an axial load to the humerus and a 45-degree diagonal elevation to the distalhumerus concurrent with a posteroinferior glide to the proximal humerus.
A positive test is indicated by a sudden onset of posterior shoulder pain.
A study by Kim 2 found that kim test has a sensitivity of 80 % and a specificity of 94 %.
Kim lesion: concealed incomplete avulsion of posteroinferior aspect of labrum.
Dhir J, Willis M, Watson L, Somerville L, Sadi J. Evidence-Based Review of Clinical Diagnostic Tests and Predictive Clinical Tests That Evaluate Response to Conservative Rehabilitation for Posterior Glenohumeral Instability: A Systematic Review. Sports Health. 2018;10(2):141-145. doi: 10.1177/ 1941738117752306. PMID: 29356622.
Kim SH, Park JS, Jeong WK, et al: The Kim test: A novel test for posteroinferior labral lesion of the shoulder- a comparison to the jerk test. The American journal of sports medicine 33:1188–92, 2005. PMID: 16000664
Clinical Tests for the Musculoskeletal System 3rd Edition.
Millers Review of Orthopaedics, 7th Edition.
Dutton’s Orthopaedic Examination, Evaluation, And Intervention 3rd Edition.
Netter’s Orthopaedic Clinical Examination An Evidence-Based Approach 3rd Edition Book.