Clonus is tested clinically by which maneuver?

Clonus is tested clinically by which maneuver?

• A. Quick plantarflexion of the ankle
• B. Brisk dorsiflexion of the ankle with observation for sustained oscillations
• C. Passive knee flexion
• D. Hip rotation

Answer: (B)

Clonus is a sign of upper motor neuron dysfunction and reflects an exaggerated stretch reflex. The test uses a rapid dorsiflexion of the ankle while the knee is extended and watching for sustained, rhythmic oscillations of the foot. If clonus is present, the calf muscles repeatedly contract in response to the rapid stretch, producing a series of beats that can continue for several seconds. This occurs because the normal inhibitory input to the reflex pathway is diminished, leading to heightened motor excitability. Other maneuvers don’t produce these sustained oscillations. Quick plantarflexion of the ankle doesn’t stretch the dorsiflexors in the same rapid, sustained way, and passive knee flexion or hip rotation aren’t focused on eliciting the ankle stretch reflex. That’s why the brisk dorsiflexion with observation for persistent oscillations is the method that best reveals clonus.

Clonus is a sign of upper motor neuron dysfunction and reflects an exaggerated stretch reflex. The test uses a rapid dorsiflexion of the ankle while the knee is extended and watching for sustained, rhythmic oscillations of the foot. If clonus is present, the calf muscles repeatedly contract in response to the rapid stretch, producing a series of beats that can continue for several seconds. This occurs because the normal inhibitory input to the reflex pathway is diminished, leading to heightened motor excitability.

Other maneuvers don’t produce these sustained oscillations. Quick plantarflexion of the ankle doesn’t stretch the dorsiflexors in the same rapid, sustained way, and passive knee flexion or hip rotation aren’t focused on eliciting the ankle stretch reflex. That’s why the brisk dorsiflexion with observation for persistent oscillations is the method that best reveals clonus.