The foot of a newborn baby has no bones per se. All future bones are there in the form of cartilage. The complex network of muscles and ligaments is in full development.
The cartilage, however, has the shape of the bones to come. Very fragile and malleable, cartilage will evolve into bone over time. At the age of 10 months, for example, bone formation is only beginning. By the time the child is three years of age, the bones will have taken shape but they will still partly be made of cartilage. It is only by the age of 21 that the foot will be completely shaped!