Test library › Shoulder & upper arm
Jerk test
For: Posteroinferior labral lesion
Website-only test: not part of the book.
A tear of the labrum, the rim of cartilage around the shoulder socket, at the back and lower part of the socket. It is linked with the shoulder slipping backwards (posterior instability).
Treat with caution (see below)Counts rebuilt from the study's published predictive values (22 of 30 lesions positive; 3 of 142 shoulders without a lesion positive); specificity and likelihood ratios calculated from them. The rounded 73% and 98% would give an LR+ of about 36.
Caution: Single study (the Kim test developers' comparison) with only 30 lesions; the LR+ rests on about 3 false positives.
These figures have not been confirmed against the full paper (checked against the abstract or a secondary source only).
How it is done
Patient sitting, arm at 90° abduction and internal rotation. The examiner stabilises the shoulder blade, applies an axial load along the humerus through the elbow and moves the arm horizontally across the body. Positive, as defined in the study for both tests: a sudden onset of posterior shoulder pain and a click, with or without a clunk.
What the studies found
Posteroinferior labral lesion. From the Kim et al. 2005 study (172 painful shoulders, 30 lesions at arthroscopy), where the jerk test was the comparison test: sensitivity 73%, specificity 98% as published. It was more sensitive than the Kim test for lesions mainly at the back of the labrum; using both tests together raised sensitivity to 97%. Single study; the high LR+ rests on very few false positives.
What the numbers mean
- Positive result: see the caution above before relying on this result.
- Negative result: a small shift: a negative result nudges the diagnosis down, but does not exclude it.
The ladder: what a result does to your estimate
| If you thought | After a positive | After a negative |
|---|---|---|
| 10% | 79% | 3% |
| 30% | 94% | 10% |
| 50% | 97% | 21% |
Calculated from the likelihood ratios above. Read the caution above before relying on these. For any other starting estimate, use the probability calculator.
Work out what a result means for your patient: probability calculator
Other tests in the library for posteroinferior labral lesion
Source
Kim SH, Park JS, Jeong WK, Shin SK. The Kim test: a novel test for posteroinferior labral lesion of the shoulder—a comparison to the jerk test. Am J Sports Med. 2005;33(8):1188–1192. Journal article (DOI) · single study
Website-only test: added to the library on 9 October 2026 and not part of Rule It In, Rule It Out. Figures independently checked against the sources cited above; any note above says where only the abstract could be checked. If a newer or better study changes them, this page will be updated.
Get the book for the shoulder questions that matter: neck or shoulder, a painful cuff or a torn one, and an unstable joint or the labrum
This test is in the website library only; it is not one of the tests in Rule It In, Rule It Out. The book covers the tests in its ‘The shoulder’ chapter: how to do each one, what counts as positive, and how to read the result.
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