How to assess for clonus?

• A. Nurse dorsiflexes the foot with one hand and supports the leg/ankle with the other. when positive clonus is shown, rhythmic jerking beats of the foot are present as the foot is released
• B. Inspect for tremor with finger tapping
• C. Check Babinski sign by stroking sole of foot
• D. Assess through deep knee bend

Answer: (A)

Clonus is an upper motor neuron sign reflecting heightened reflex responsiveness. To assess it, the clinician gently dorsiflexes the ankle with one hand while stabilizing the leg with the other. If clonus is present, after releasing the dorsiflexion, you’ll observe rhythmic, repetitive foot (ankle) contractions—jerking beats—as the foot returns toward the plantar position. This rhythmic movement confirms clonus and suggests UMN pathway disruption.

Tremor with finger tapping isn’t clonus; it assesses tremor behavior rather than a stretch-induced reflex. Babinski involves stroking the sole to elicit an abnormal plantar response, not rhythmic clonic activity. A deep knee bend evaluates strength and neuromuscular control of the leg, not clonus.