Pronation is the normal motion that allows the foot to adapt to uneven walking surfaces and to absorb shock. Excessive pronation occurs when the foot has a tendency to turn inwardly and stretch and pull the fascia. It can cause not only heel pain, but hip, knee, and lower back problems. Flatfoot, or pes planus, is a defect of the foot, in which there is no arch at all. Flatfoot is usually hereditary or caused by diseases of the muscles and nerves.
Arches can fall, however, under certain conditions.
At particular risk are women who have habitually worn high-heels for long periods. In such cases, the Achilles tendon that runs down the back of the calf to the heel bone is not stretched, so over the years, it shortens and tightens. The ankle, then, does not bend properly, and tendons and ligaments running through the arch try to compensate. Sometimes, they then break down and the arch falls. Some studies have indicated that the earlier one starts wearing shoes, particularly for long periods of the day, the higher the risk for flat feet.