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the knee jerk, in which stretching the muscle at the front of the thigh by tapping its tendon below the knee cap causes a reflex contraction of the muscle, so that the leg kicks. This is a test of the connection between the sensory nerves attached to stretch receptors in the muscle, the spinal cord, and the motor neurones running from the cord to the thigh muscle, all of which are involved in the reflex. Disease or damage may result in absence of the reflex.
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contraction of the quadriceps and extension of the lower limb when the patellar ligament is tapped; called also knee jerk, quadriceps jerk, knee jerk r., and quadriceps r.
Eliciting the patellar reflex.
Medical dictionary. 2011.