Kernig sign is one of the eponymous clinical signs of meningitis or meningism. This is a common test and is typically performed while the patient is supine with the hips flexed. It is described as resistance to or pain with passive extension of the knees in cases of suspected meningitis .
Kernig sign and Brudzinski sign, often concurrently sought in suspected meningitis, have a limited role in ruling out meningitis with sensitivities as low as 5% however specificities as high as 95% have been reported .
Although initially described by Kernig with patient sitting, clinicians typically have the patient laying supine with the hips and knees flexed . The examiner passively extends the knees. In the presence of meningeal inflammation the patient will typically resist extension or describe pain in the lower back or posterior compartment of the thighs. This is considered a positive sign.
Along with Brudzinski sign, it demonstrates poor sensitivity but moderate to high specificity .
History and etymology
Kernig sign was described in the 19th century by Russian physician Vladimir Kernig . Kernig observed that patients with bacterial or tuberculous meningitis were unable to completely extend their legs while sitting upright and first reported the sign at a medical congress in St. Petersburg in 1882 .