膝蓋骨[shitsugaikotsu] kneecap
膝蓋腱反射[shitsugaikenhansha] kneecap (patellar) reflex
膝関節[shitsukansetsu] knee joint
膝がしら[hizagashira] kneecap
片膝[katahiza] one knee

諸膝[morohiza] both knees
膝小僧[hizakozou] kneecap
膝許[hizamoto] near one's knee
膝行[shikkou] moving forward by sliding on one's knees (in the presence of high-ranking individuals)