Which sign is described as neck flexion causing involuntary flexion of the hips and knees?

• A. Kernig sign
• B. Brudzinski sign
• C. Nuchal rigidity
• D. Neck flexion causing involuntary flexion of the hips and knees

Answer: (D)

Brudzinski sign tests for meningeal irritation. When you passively flex the patient's neck, the hips and knees involuntarily flex in response. This reflexive lower-limb movement happens because stretching the meninges triggers a flexor reflex in the legs, which is characteristic of Brudzinski sign. It’s distinct from Kernig sign, which involves pain and resistance to extending the knee when the hip is flexed, and from nuchal rigidity, which is simply stiff neck without that reflex response. So the described description matches Brudzinski sign.