Definition of Pes planus:

Pes planus is a condition in which the arch or instep of the foot collapses and comes in contact with the ground. In some individuals, this arch never develops while they are growing.

Causes, incidence, and risk factors:

Flat feet are a common condition. In infants and toddlers, the arch is not developed and flat feet are normal. The arch develops in childhood. By adulthood, most people have developed normal arches.

When flat feet persist, most are considered variations of normal. Most feet are flexible and an arch appears when the person stands on his or her toes. Stiff, inflexible, or painful flat feet may be associated with other conditions and require attention.

Painful flat feet in children may be caused by a condition called tarsal coalition. In tarsal coalition, two or more of the bones in the foot fuse together. This limits motion and often leads to a flat foot.

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

Foot pain, ankle pain, or lower leg pain (especially in children) may be a result of flat feet and should be evaluated by a health care provider.

Adults can develop a flat foot when they are 60-70 years old. This type of flat foot is usually on one side.