Definition of Pes planus:

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

Causes, incidence, and risk factors:

Flat feet are a common condition. In infants and toddlers, the longitudinal arch is not developed and flat feet are normal. The arch develops in childhood, and 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, limiting motion and often leading to a flat foot.

Most flat feet 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 by a health care provider.