Stone Man Syndrome is an extremely rare condition whereby any small damage to tissue is regrown into bone.– WTF Fun Facts
bone
WTF Fun Fact – Baby Knees
Babies are born without knee caps. The cartilage begins to ossify and form the knee cap between 2 and 6 years of age. – WTF Fun Facts
Source: https://www.healthline.com/health/do-babies-have-kneecaps