Which statement describes Kernig sign?

• A. Pain in the lower back when the leg is extended
• B. Dorsal root signs with straight leg raise
• C. Pain upon extending the knee with the thigh flexed at 90 degrees
• D. Visual disturbances

Answer: (C)

Kernig sign comes from meningeal irritation, such as in meningitis or subarachnoid hemorrhage. To test it, you have the patient lie on their back, flex the hip to 90 degrees, and then attempt to straighten the knee. If extending the knee causes pain or a noticeable resistance, that’s a positive sign. The pain results from stretching inflamed meninges and the nerve roots when the leg is extended with the hip held at 90 degrees. This distinguishes meningeal irritation from a simple knee or back issue. The other scenarios describe different leg-raising tests or unrelated symptoms, which do not reflect Kernig sign.