This test looks for involuntary oscillations in muscle contraction in response to tonic stretch, suggestive of upper motor neuron lesions

Performing the Test

  1. Have the patient lie supine while supporting their leg at the knee
  2. Ask the patient to relax their leg while you dorsiflex and plantarflex the ankle
  3. Suddenly, briskly dorsiflex the patient’s ankle and hold it in that position
  4. Positive clonus will present as rhythmic oscillations between plantarflexion and dorsiflexion of the ankle
  5. Sustained clonus suggests an upper motor neuron lesion


  1. Insall, RL, Davies RJ, Prout WG. Significance of Buerger’s test in the assessment of lower limb ischaemia. J R Soc Med. 1989; 82:729-731