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Patellar clonus - clinical significance

Patellar clonus is a clinical sign of pyramidal tract dysfunction.It is usually associated with exaggerrated reflex and extensor plantar reflex.
How to elicit the patellar clonus?
  • Patient lies supine with knee extended.
  • Fix the leg with one hand
  • Patella is pulled upwards with a fold of  skin behind the palm.
  • Now a sharp and sudden displacement of the patella downwards by the index finger and thumb( sustained pressure is applied) will produce series of quadriceps contraction.

It is also known as knee clonus.
It is seen in pyramidal tract lesions
Ankle and patellar clonus are produced as a result of loss of upper motor control (ie. UMN lesion) over S1