kneecap vs knee

kneecap and knee both are nouns.

Word	Noun	Adjective	Verb	Adverb
kneecap	Yes	No	Yes	No
knee	Yes	No	No	No

kneecap (noun)	knee (noun)
a small flat triangular bone in front of the knee that protects the knee joint	joint between the femur and tibia in a quadruped; corresponds to the human knee
	the part of a trouser leg that provides the cloth covering for the knee
	hinge joint in the human leg connecting the tibia and fibula with the femur and protected in front by the patella

kneecap (verb)	knee (verb)
shoot in the kneecap, often done by terrorist groups as a warning