Before the age of 3, the foot bones are 70% cartilage, the arch has not yet formed, and the sole of the foot is flat and normal due to the fat pad;
at 3 years old, the arch begins to develop, and at 9 years old, the arch gradually forms,
and by 12-13 years old, the arch bones have basically developed and matured, and the arch function is basically stable, which is the golden period of arch development.
If the child's foot is still flat after 3 years old, the arch development may be abnormal, and it needs to be adjusted and exercised according to its degree.
3-12 years old is also the best period for gait adjustment, as it is the period of rapid skeletal growth.