knee jerk vs inborn reflex

knee jerk and inborn reflex both are nouns.

Word	Noun	Adjective	Verb	Adverb
knee jerk	Yes	No	No	No
inborn reflex	Yes	No	No	No

As nouns, inborn reflex is a hypernym of knee jerk; that is, inborn reflex is a word with a broader meaning than knee jerk:

knee jerk: a reflex extension of the leg resulting from a sharp tap on the patellar tendon
inborn reflex: an automatic instinctive unlearned reaction to a stimulus

knee jerk (noun)	inborn reflex (noun)
a reflex extension of the leg resulting from a sharp tap on the patellar tendon	an automatic instinctive unlearned reaction to a stimulus