Flat feet are a common condition. In infants and toddlers, the longitudinal arch is not developed and flat feet are normal. Most feet are flexible and an arch appears when the person stands on his or her toes. The arch develops in childhood, and by adulthood most people have developed normal arches.

Most flat feet usually do not cause pain or other problems. Flat feet may be associated with pronation, a leaning inward of the ankle bones toward the center line. Shoes of children who pronate, when placed side by side, will lean toward each other (after they have been worn long enough for the foot position to remodel their shape).

Foot pain, ankle pain or lower leg pain, especially in children, may be a result of flat feet and should be evaluated.

Painful progressive flatfoot, otherwise known as Tibialis Posterior Tendonitis, is caused by inflammation of the tendon of the tibialis posterior. The tendon then becomes inflamed, stretched or suffers a partial or total tear. If left untreated, this condition may lead to severe disability and chronic pain. Some people are predisposed to this condition if they have flatfeet or an abnormal attachment of the tendon to the bones in the midfoot.