Which description defines the Kernig sign?

Which description defines the Kernig sign?

• A. The knee extension causes pain when the thigh is flexed at 90 degrees.
• B. Neck flexion causes flexion of the hips and knees.
• C. Pain is elicited by straightening the knee when the thigh is extended.
• D. Pain occurs when extending the knee with the thigh flexed at 90 degrees.

Answer: (D)

Kernig sign indicates meningeal irritation, such as meningitis. The test is performed with the person lying flat, the hip flexed to 90 degrees, and then the knee is extended. If extending the knee in that position causes pain or resistance, the sign is considered positive. The description “pain occurs when extending the knee with the thigh flexed at 90 degrees” matches this test exactly, capturing the essential hip flexion followed by knee extension that provokes the symptom. This helps distinguish it from related signs like Brudzinski, where neck flexion induces hip and knee flexion, not knee extension in a flexed hip.

Kernig sign indicates meningeal irritation, such as meningitis. The test is performed with the person lying flat, the hip flexed to 90 degrees, and then the knee is extended. If extending the knee in that position causes pain or resistance, the sign is considered positive. The description “pain occurs when extending the knee with the thigh flexed at 90 degrees” matches this test exactly, capturing the essential hip flexion followed by knee extension that provokes the symptom. This helps distinguish it from related signs like Brudzinski, where neck flexion induces hip and knee flexion, not knee extension in a flexed hip.