Babies have far more cartilage in their skeletons than adults do. According to Dr. Eric Edmonds of Rady Children's Hospital, most children's kneecaps begin to ossify — turn from cartilage into bone — between the ages of 2 and 6. This is a slow process that takes many years.

At what age does the kneecap form?

When the child is somewhere between 2 and 6 years old, their cartilage patella starts forming a center of bone. Often, the kneecap will start to form bone at multiple centers within the cartilage. About 5 percent of the time, some of these bone centers do not fuse together with the main bone center.

How long do babies not have kneecaps?

The process of the patella turning from cartilage to bone is called ossification, and is usually complete by the time your child enters the elementary school years. “The kneecaps transition to bone between 2 and 6 years of age,” Dr. Poinsett explains.