What is "patellar reflex"

Reflex \Re"flex\ (r?"fl?ks; formerly r?*fl?ks"), n. [L. reflexus a bending back. See Reflect.]

1. Reflection; the light reflected from an illuminated surface to one in shade.

   Yon gray is not the morning's eye, 'Tis but the pale reflex of Cynthia's brow.
   --Shak.

   On the depths of death there swims The reflex of a human face.
   --Tennyson.

2. (Physiol.) An involuntary movement produced by reflex action.

   Patellar reflex. See Knee jerk, under Knee.

n. The reflex which causes a bent knee to kick when the tendon below the patella (kneecap) is tapped.

n. a reflex extension of the leg resulting from a sharp tap on the patellar tendon [syn: knee jerk, knee-jerk reflex]

The patellar reflex or knee-jerk (American spelling knee reflex) is a stretch reflex which tests the L2, L3, and L4 segments of the spinal cord.