Kernig's sign

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|caption = Positive Kernig's sign in meningitis

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|differential = subarachnoid hemorrhage or meningitis

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Kernig's sign is a test used in physical examination to look for evidence of irritation of the meninges. The test involves flexing the thighs at the hip, and the knees, at 90 degree angles, and assessing whether subsequent extension of the knee is painful (leading to resistance), in which case it is deemed positive.{{cite journal|author=Kernig VM|year=1882|title=Ein Krankheitssymptom der acuten Meningitis|journal=St Petersb Med Wochensch|volume=7|pages=398}} This may indicate subarachnoid haemorrhage or meningitis.{{cite book|title=Clinical Examination: A Systematic Guide to Physical Diagnosis|author=O'Connor, Simon|author2=Talley, Nicholas Joseph|publisher=Blackwell Publishers|year=2001|isbn=0-632-05971-0|location=Cambridge, MA|page=363}} Patients may also show opisthotonus—spasm of the whole body that leads to legs and head being bent back and body bowed forward.{{Citation|last=Shahade|first=Arati|title=Opisthotonus|date=2020|url=http://www.ncbi.nlm.nih.gov/books/NBK559170/|work=StatPearls|place=Treasure Island (FL)|publisher=StatPearls Publishing|pmid=32644596|access-date=2021-01-10|last2=De Jesus|first2=Orlando}}

Karl et al. noted much of the literature on Kernig's sign is old and they could find no randomised trials of it. They also noted low sensitivity of 5% meaning absence of Kernig's sign does not rule out meningitis, specificity however is 95% so if positive then meningitis is very likely. Kernig's should not be relied on when meningitis is suspected and a lumbar puncture should be performed. {{Citation|last=Karl|first=Alyssa|title=Kernig Sign|date=2022|url=http://www.ncbi.nlm.nih.gov/books/NBK470365/|work=StatPearls|place=Treasure Island (FL)|publisher=StatPearls Publishing|pmid=29262005|access-date=2022-02-17|last2=Ali|first2=Muhammad Ashar|last3=Brandis|first3=Dov}}