The next time you step out of the bath tub or shower, notice the tracks made by your wet feet. If the tracks are kidney-shaped, your foot is normal. If the prints your feet make have the shape of a sole, because the entire sole touches the floor, you have flat feet.

The foot is a tripod, because it stands on three points. One is the heel in back. The other two are the two supporting points in the ball of the foot. Over these three points the foot forms an arch. This arch is not firm, but is elastic and springy. This is due to the arrangement of the bones, cartilage, ligaments, tendons, and muscles of the foot.