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Patellar reflex

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Definition

noun, plural: patellar reflexes

A stretch reflex wherein the anterior muscles of the thigh contracts by reflex as a response to a smart tap on the patellar tendon while the leg hangs loosely at a right angle with the thigh


Supplement

A stretch reflex is a reflex reaction characterized by muscle contraction due to the stimulation of the muscle proprioceptors. When the muscle is stretched, the body reacts by resisting the stretch by reflex. Some of the stretch reflexes are jaw jerk reflex, biceps reflex, brachioradialis reflex, triceps reflex, patellar reflex, and ankle jerk reflex.

A patellar reflex is a form of stretch reflex involving the L2, L3, and L4 segments of the spinal cord. It is applied in neurological examination to determine the status of the nerves in those regions. The test is done by striking the patellar tendon with a reflex hammer while the leg hangs loosely at a right angle with the thigh. This elicits a reflex reaction involving the anterior muscles of the thigh. The muscle contracts leading to the oscillation of the leg once, and then rests. The absence of this reflex may be an indication of a neurologic problem or an underlying medical condition such as lower motor neuron lesion. This reflex though is absent during sleep. Too many leg oscillations following the tap may be an indication of a cerebral disease.



Synonym(s):

  • knee jerk
  • knee phenomenon
  • knee reflex
  • knee-jerk reflex
  • patellar tendon reflex
  • quadriceps reflex

See also: