Kernig's sign is elicited by flexing the hip to 90 degrees and then attempting to extend the knee. Resistance or pain that prevents extension is a positive result, and it has been taught as a bedside indicator of meningeal irritation for well over a century.
It is worth learning and worth performing. It is not worth trusting on its own: the modern accuracy data for Kernig's and Brudzinski's signs is poor enough that a negative examination does very little to lower the probability of meningitis in a patient whose history suggests it.
Zdrovia — https://www.zdrovia.ca/resources/kernigs-sign/
Clinical Sign Reference
Meningeal Irritation Sign Comparator
Technique, positive finding, and reported accuracy for the four bedside signs — and what a result actually changes.
Other clinical features present
Kernig's sign
Technique
Patient supine. Flex one hip to 90 degrees with the knee also flexed, then attempt to passively extend the knee while the hip stays flexed. Repeat on the other side.
Positive finding
Resistance to knee extension, or pain in the lower back or posterior thigh that limits it.
Mechanism
Stretch on inflamed lumbosacral nerve roots and meninges.
Reported sensitivity
~5%
Proportion of affected patients detected
Reported specificity
~95%
Proportion of unaffected correctly negative
What this result changes
All four signs compared
| Sign | Manoeuvre | Sensitivity | Specificity |
|---|---|---|---|
| Kernig's sign | Knee extension | ~5% | ~95% |
| Brudzinski's sign | Neck flexion | ~5% | ~95% |
| Nuchal rigidity | Neck stiffness | ~30–70% | ~50–70% |
| Jolt accentuation | Head rotation | Reported 60–100%, not consistently reproduced | ~50–70% |
These results are estimates based on published clinical data and are for informational purposes only. They do not constitute medical advice, a diagnosis, or a treatment recommendation. Consult a licensed aesthetic practitioner before beginning any treatment. Individual results vary.
Zdrovia's smart blocks put Kernig's, Brudzinski's, and nuchal rigidity findings into the note as structured fields rather than free text. See how smart blocks work →
Document meningeal signs as you examine
Zdrovia's smart blocks put Kernig's, Brudzinski's, and nuchal rigidity findings into the note as structured fields rather than free text.
How to elicit Kernig's sign
With the patient supine, flex one hip to 90 degrees with the knee also flexed. Then attempt to passively extend the knee while the hip stays flexed. A positive sign is resistance to extension, or pain in the lower back or posterior thigh that limits it. Compare both sides.
The mechanism is stretch on inflamed lumbosacral nerve roots and meninges. That same mechanism means the sign is not specific to meningitis — lumbar radiculopathy, hamstring tightness, and hip pathology all produce resistance to knee extension in a flexed hip, and none of them involve the meninges.
The accuracy problem
The best-known prospective evaluation of these signs, by Thomas and colleagues in 2002, found sensitivity of roughly 5% for both Kernig's and Brudzinski's signs in adults with suspected meningitis. Specificity was high, around 95%, but a test that is positive in only a twentieth of affected patients cannot be used to exclude the diagnosis.
Nuchal rigidity performs somewhat better on sensitivity but remains far from reliable. Jolt accentuation of headache — asking the patient to rotate the head horizontally two to three times per second and noting whether the headache worsens — was reported with high sensitivity in early work, but subsequent studies have not consistently reproduced that finding.
The practical rule follows directly: a positive sign meaningfully raises your suspicion, and a negative one barely lowers it. Where meningitis is a serious consideration, the examination does not substitute for investigation.
What to do with a suspicion of meningitis
Bacterial meningitis is a medical emergency in which time to antibiotics is strongly associated with outcome. If the clinical picture raises the possibility, that suspicion drives urgent escalation and empirical treatment — not further bedside manoeuvres.
This page is a reference for how the classic signs are performed and what they are worth. It is not a decision rule, and it is not a substitute for local emergency protocols or for the judgement of the clinician in front of the patient.