The answer to this depends on how you define the kneecap. Babies are not born with a kneecap like an adult’s – but then, very little of their body is like an adult’s. A majority of a baby’s body at birth is cartilage. This is why babies and toddlers can bend in ways that make grown-ups cringe. Their skull is made up of moving plates that don’t become hard until several years later, and the kneecap is very much like that.
A baby’s kneecap is cartilage. As the baby grows, the cartilage slowly changes to bone. For girls, they’ll have a "normal" kneecap of bone by around age three, assuming normal calcium intake. Boys’ kneecaps don’t turn fully from cartilage to bone until around age 5.
So the form of the knee and the kneecap is there, it’s just made of a different material.
A baby’s kneecap is cartilage. As the baby grows, the cartilage slowly changes to bone. For girls, they’ll have a "normal" kneecap of bone by around age three, assuming normal calcium intake. Boys’ kneecaps don’t turn fully from cartilage to bone until around age 5.
So the form of the knee and the kneecap is there, it’s just made of a different material.