noun
patellar reflex; knee-jerk reflex
Medical term for the reflex contraction of the quadriceps when the patellar tendon is tapped.
医師は膝蓋腱反射を調べるために膝を叩いた。
The doctor tapped the knee to test the patellar reflex.
Compound of 膝蓋 (しつがい, 'patella') + 腱 (けん, 'tendon') + 反射 (はんしゃ, 'reflex').