Infants, 0 to 2 years
The foot is very soft and flexible. The bones are not yet 'connected', and the arches are not yet developed - there's a large amount of fatty tissue and underdeveloped muscle, which gives the foot a 'flat-footed' look. A wide fore foot is the characteristic shape at this stage.
Children, 2 to 7 years
The foot continues to be soft and flexible. The arches are now beginning to develop, along with the muscles. The shape of the foot begins to narrow, but the forefoot is still wider in comparison to an adult foot.
Juniors, 8 to 12 years
Some of the flexibility has gone, but the foot is still very pressure sensitive. The arches are almost fully developed, giving the foot an adult-like shape. But the forefoot is still comparitively wide.
