Flat Feet

Flat feet (pes planus) is a condition in which the foot does not have a normal arch when standing.

Causes, incidence, and risk factors

Flat feet are a common condition. In infants and toddlers, they are normal. Flat feet occur because the tissues holding the joints in the foot together (called tendons) are loose. In infants and babies, the fat in the foot is also a factor. As children grow older, these tissues tighten and form an arch, most often by the time the child is 2 or 3 years old. By adulthood, most people have normal arches. However, in some people this arch may never form.

Ageing, injuries, or illness may harm the tendons and cause flat feet to develop in a person who has already formed arches. This type of flat foot may only be on one side. Rarely, painful flat feet in children may be caused by a condition in which two or more of the bones in the foot grow or fuse together. This condition is called tarsal coalition.


Most flat feet do not cause pain or other problems. At times, foot pain, ankle pain, or lower leg pain are present (especially in children). They should be evaluated by a health care provider.

Adults may notice some symptoms. Their feet may become achy or tired when standing for long periods of time or after playing sports.

Signs and tests

In people with flat feet, the instep of the foot comes in contact with the ground when they stand. The health care provider will ask you to stand on your toes. If an arch forms while you are standing on your toes, the flat foot is called flexible. No treatment or further work-up is needed. If the arch does not form with toe-standing (called rigid flat feet), or if there is pain, other tests may be needed, including:

  • CT scan to look at the bones in the foot
  • MRI scan to look at the tendons in the foot
  • X-ray of the foot