knee-jerk reflex

knee-jerk reflex

▪ medical test
also called  patellar reflex 

      sudden kicking movement of the lower leg in response to a sharp tap on the patellar tendon, which lies just below the kneecap. One of the several positions that a subject may take for the test is to sit with knees bent and with one leg crossed over the other so that the upper foot hangs clear of the floor. The sharp tap on the tendon slightly stretches the quadriceps, the complex of muscles at the front of the upper leg. In reaction these muscles contract, and the contraction tends to straighten the leg in a kicking motion. Exaggeration or absence of the reaction suggests that there may be damage to the central nervous system. The knee jerk can also be helpful in recognizing thyroid disease.

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Universalium. 2010.

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Look at other dictionaries:

  • knee-jerk reflex — noun a reflex extension of the leg resulting from a sharp tap on the patellar tendon • Syn: ↑knee jerk, ↑patellar reflex • Hypernyms: ↑reflex, ↑reflex response, ↑reflex action, ↑instinctive reflex, ↑ …   Useful english dictionary

  • knee jerk reflex — patellar r …   Medical dictionary

  • Knee jerk — The reflex tested by tapping just below the knee causing the lower leg to suddenly jerk forward. What is tapped to elicit this reaction is the patellar tendon, the tendon that runs down from the quadriceps muscle in the front of the thigh, over… …   Medical dictionary

  • knee jerk — noun a reflex extension of the leg resulting from a sharp tap on the patellar tendon • Syn: ↑knee jerk reflex, ↑patellar reflex • Hypernyms: ↑reflex, ↑reflex response, ↑reflex action, ↑instinctive reflex, ↑ …   Useful english dictionary

  • Knee jerk — (Physiol.) A jerk or forward kick of the lower part of the leg produced by a blow or sudden strain upon the patellar tendon of the knee, which causes a sudden contraction of the quadriceps muscle; the patellar reflex. [Webster 1913 Suppl.] …   The Collaborative International Dictionary of English

  • knee-jerk — ► NOUN ▪ an involuntary reflex kick caused by a blow on the tendon just below the knee. ► ADJECTIVE ▪ automatic and unthinking: a kneejerk reaction …   English terms dictionary

  • knee-jerk — patellar reflex, neurological phenomenon discovered and named 1876; the figurative use appeared soon after the phrase was coined …   Etymology dictionary

  • knee jerk — knee′ jerk n. phl a reflex extension of the leg resulting from a sharp tap on the patellar tendon • Etymology: 1875–80 …   From formal English to slang

  • knee jerk — n. PATELLAR REFLEX …   English World dictionary

  • knee-jerk — ¦ ̷ ̷ (ˌ) ̷ ̷ adjective Etymology: knee jerk, noun : readily predictable : automatic knee jerk reactions also : reacting in a readily predictable way knee jerk liberals * * * /nee jerrk / …   Useful english dictionary

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