We thank Robert T. Manning, MD for valuable information concerning Kernig's sign, and the English translation from Kernig's original text. It seems that Kernig's sign is often wrongly described.
A sign in acute meningitis.
This is Kernig's original description:
"I have observed for a number of years in cases of Meningitis a symptom which is apparently rarely recognized although, in my opinion, it is of significant practical value. I am referring to the occurrence of flexion contracture in the legs or occasionally also in the arms which becomes evident only after the patient sits up....the stiffness of neck and back will ordinarily become much more severe and only now will a flexion contracture occur in the knee and occasionally also in the elbow joints. If one attempts to extend the patient’s knees one will succeed only to an angle of approximately 135o. In cases in which the phenomenon is very pronounced the angle may even remain 90o."
Robert T Manning comments:
"Most physicians have forgotten that the major causes of meningitis in Kernig’s days were pneumococcus and tuberculosis which both produce an intense pachymeningitis around the brain stem---thus the pathophysiology of the sign.
These days, viral meningitis is the most common form seen---no pachymenigitis—and a negative Kernig’s sign."
- V. M. Kernig:
Ein Krankheitssymptom der acuten Meningitis.
St. Petersburger medicinische Wochenschrift, 1882, 7: 398.
Protokolle des Allgemeinen Verein St. Petersburg Aertze.
Minutes of the General Physicians Club of St. Petersburg. Über ein wenig bemerktes Meningitis-Symptom.
Berliner klinische Wochenschrift, 1884, 21: 829-832. Über die Fraktur im Kniegelenk bei Meningitis.
Zeitschrift für klinische Medizin, Berlin, 1907, 64: 19.