Longman Dictionary of Contemporary English
knee cap
noun
EXAMPLES FROM CORPUS
▪ Indiana was without Patterson, its leading scorer and rebounder, because of a slight dislocation of his left knee cap.
▪ Jokes about the subject suggest the punch-line might be followed by the odd shattered knee cap.
Wiktionary
knee cap
n. 1 (context roofing English) A metal cover trim that fits over a panel rib after it has been cut and bent. 2 (context rare English) (alternative spelling of kneecap English)
Usage examples of "knee cap".
Grave Digger backhanded with the same motion that tapped Roman on the head and hit his right knee cap.
Malise agreed and moved in, pulling strings, getting Jake instantly transferred to the Motcliffe in Oxford, where the X-rays showed the knee cap was shattered and the leg broken in five places.