A 'flat foot' has a low arch and is not actually a foot problem. Having flat feet does not necessarily impair one's ability to run. Flat feet seldom cause any problems; however, they can cause pain usually in the calf, knee, or lower back and is often the result of standing for long periods of time. Flat feet are also more prone to bunions and arch pain.
As with flat feet high arched feet are not necessarily a problem. However people with high arches are more likely develop other foot problems, specifically hammer toes and associated calluses and corns.