Flat feet are a common condition of the foot structure. In infants and toddlers, prior to walking, the longitudinal arch is not developed and flat feet are normal. Most feet are flexible and an arch appears when children begin standing on their toes. The arch continues to develop throughout childhood, and by adulthood most people have developed normal arches.

Flat feet are generally 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).

Many people with flat feet do not experience pain or other problems. When pain in the foot, ankle, or lower leg does occur, especially in children, the feet should be evaluated.
Painful progressive flatfoot, otherwise known as tibialis posterior tendonitis or adult acquired flatfoot, refers to inflammation of the tendon of the tibialis posterior. This condition arises when the tendon becomes inflamed, stretched, or torn. Left untreated, it may lead to severe disability and chronic pain. People are predisposed to tibialis posterior tendonitis if they have flat feet or an abnormal attachment of the tendon to the bones in the midfoot.

Nonsteroidal anti-inflammatory medications, icing, physical therapy, supportive taping, bracing, and orthotics are common treatments for painful progressive flatfoot. Note: Please consult your physician before taking any medications. In some cases, a surgery may need to be performed to repair a torn or damaged tendon and restore normal function. In the most severe cases, surgery on the midfoot bones may be necessary to treat the associated flatfoot condition.