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Patellar reflex (L-4 Motor)

Name of test

Patellar reflex (knee jerk)

What it tests

Whether the L4 nerve root is intact

How to do it

  • In the sitting position, the patient allows his/her knee to be flexed without contracting the muscle.
  • The clinician taps the patellar tendon with a reflex hammer just above the tibial tuberosity.

The normal response

Normal patellar reflex (knee jerk) of 1-2/4

What it means if not normal

Disruption in the monosynaptic reflex arc



Hoppenfeld, Stanley. Orthopaedic Neurology. Philadelphia: J.B. Lippincott Co., 1997.

K. Anderson, J. Hall. Sports Injury and Management: Philadelphia: Williams & Wilkins,1995.

Reider, Bruce. The Orthopaedic Physical Examination, 2nd Ed.: Philadelpiha: Elsevier Saunders, 2005.

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