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.

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.

• Absence of longitudinal arch of foot when standing
• Foot pain
• Heel tilts away from the midline of the body more than usual

Examination of the foot is sufficient for the health care provider to make the diagnosis of flat foot. However, the underlying cause must be determined. If an arch develops when the patient stands on their toes, then the flat foot is called flexible and no treatment or further work-up is necessary.

If there is pain associated with the foot or if the arch does not develop with toe-standing, X-rays are necessary. If a tarsal coalition is suspected, a CT scan is often ordered. If a posterior tibial tendon injury is suspected, your health care provider may recommend an MRI.

Flexible flat feet that are painless do not require treatment. If pain due to flexible flat feet occurs, an orthotic (arch supporting insert in the shoe) can bring relief. With the increased interest in running, many shoe stores carry shoes for normal feet and pronated feet. The shoes designed for pronated feet make long distance running easier and less tiring as they correct for the positional abnormality.

Rigid or painful flat feet require the evaluation of a health care provider. The exact treatment depends on the cause of the flat feet. For tarsal coalition, treatment starts with rest and possibly casting.

If this fails to improve the pain, surgery may be necessary to either resect the fused bone or actually completely fuse several bones in a corrected position. For problems with the posterior tibial tendon, treatment may start with rest, anti-inflammatory medications, and shoe inserts or ankle braces.

In more advanced cases, surgery may be necessary to clean the tendon, repair the tendon, or actually fuse some of the joints of the foot in a corrected position in very advanced cases.

Most cases of flat feet are painless and no problems are to be expected. The prognosis of painful flat feet again depends on the cause of the condition. Usually treatment is successful, regardless of the cause.

If a fusion is required then there is some loss of ankle motion, especially turning the foot inward and outward, but otherwise patients with fusions report tremendous improvement in pain and function.

Flat feet are not really associated with any complications except pain. Some causes of flat feet can be successfully treated without surgery if caught early, but occasionally, surgery is the last option to relieve pain.

While usually successful, surgery sometimes does not result in satisfactory results for all patients. Some have persistent pain and other possible surgical complications include infection and failure of fused bones to heal.

Call your health care provider if you experience persistent pain in your feet or your child complains of foot pain or lower leg pain.

Most cases are not preventable.

Hosalkar HS, Spiegel DA, Davidson RS. The Foot and Toes. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007; Chap. 673.