knee-jerk reflex knee jerk • knee joint · · · Info · Definitions · Synonyms · Characters · · knee-jerk reflex · · Text Common · · Latin · · Scripts 16 · · Length 4 · · Syllables Definitions · · · (noun) a reflex extension of the leg resulting from a sharp tap on the patellar tendon. Synonyms: knee jerk, knee-jerk reflex, patellar reflex. · · Noun Definition 1 Synonyms · · · knee jerk · · Synonym 1 patellar reflex · · Synonym 2 Characters · · space U+0020 - hyphen-minus U+002D e latin small letter e U+0065 f latin small letter f U+0066 j latin small letter j U+006A k latin small letter k U+006B l latin small letter l U+006C n latin small letter n U+006E r latin small letter r U+0072 x latin small letter x U+0078