Flat Feet Causes and Associated Medical Problems

Causes, problems, and treatment

Flattened arch from over-pronation while weight-bearing. Google Images

If you have flat feet, your arches are low or maybe even absent. The condition is also known by the medical terms "pes planus" or "pes valgus."

Flat Feet and Overpronation

Flat feet are often associated with excessive pronation, which is the action that causes the foot's arch to descend down and inward (flattening) as the foot strikes the ground. Pronation is a normal and necessary foot motion.

Overpronation, however, means that feet pronate to an excessive degree while standing, walking or running.

Because of their tendency to overpronate, flat feet are less able to absorb shock. This impaired shock-absorption can mean increased stress on the feet, ankles, and knees.

You can sometimes identify overpronation in a person with flat feet by observing them from behind. You may see something called the "too-many-toes" sign, where the individual's toes and forefeet splay outward.

  • Photo showing the too-many-toes sign.

Causes of Flat Feet

  1. Normal Developmental Changes -- As children grow, their legs will experience developmental changes that can result in excess flattening of the arches with weight bearing. One example is genu valgum, or knock-knees, a usually normal, temporary condition in children at different stages of growth. A tight calf muscle or Achilles tendon can also contribute to a flat foot. Many children will experience tight calf muscles as they go through growth spurts.
  1. Congenital Foot Abnormalities -- Conditions that are present at birth and are often diagnosed early include: metatarsus adductus, calcaneovalgus, and congenital vertical talus.
  2. Tarsal Coalitions -- Tarsal coalitions are congenitally fused foot bones that cause a rigid flat foot often associated with painful muscle spasms. This type of flat foot is usually diagnosed later in childhood or in adulthood.
  1. Loose Ligaments -- Any condition that causes loose ligaments can result in a flat foot or lower-than-normal arch. Ligaments are bands of tissue that connect bones to each other and have an important role in giving form to foot arches. An example of a condition that causes loosening of ligaments is pregnancy, where normal hormonal changes relax the ligaments. Diseases that cause loose ligaments include Ehlers-Danlos syndrome, Marfan's syndrome and rheumatoid arthritis.
  2. Leg Length Inequality -- If one leg is longer than the other, one foot may be flat in relation to the other to compensate. Usually, the foot on the longer limb will have a flatter arch in an effort to shorten that limb, balancing out the unevenness. Leg length inequality can be caused by spinal abnormalities such as scoliosis. It can also be due to an actual difference in length of one leg bone compared to the other.

Problems Often Associated with Flat Feet

When Flat Feet Require Medical Attention

If you have flat feet you may not necessarily need treatment -- sometimes a child or even an adult will have low arches and have no problems.

It's normal for a baby's or young child's feet to appear flat until the structure of their feet is more fully developed.

If flat feet are contributing to secondary problems, especially leg or foot pain, treatment may be necessary. Flat feet can sometimes cause difficulty walking or running and interfere with athletic activities. A visit to a podiatrist will involve an evaluation of foot structure and function. Besides a foot exam, a visit may include foot X-rays and an analysis of your feet while walking.

Orthotics for Flat Feet

Your podiatrist may prescribe arch supports or orthotics to control the pronation.

While orthotics and arch supports don't permanently correct the shape of the arch, they do help control excess pronation that may be causing wear-and-tear on your muscles and joints. Sneakers with a design called motion control are also helpful for overpronators. This style of sneaker has a design that creates more stability by limiting movement in the heel and arch area of the shoe. Additionally, physical therapy and stretching exercises may be in order, especially if tendonitis (tendon inflammation) is present.

Bracing, Casting and Surgery for Flat Feet

Flat feet that are the result of congenital or developmental abnormalities may require further intervention, such as bracing, casting or surgical correction.

  • A brace incorporates an arch support into a device that attaches to the lower leg, giving extra support and flat-foot control. Bracing or foot surgery may also be warranted in cases when flat feet are caused by neurological diseases or are aggravated by posterior tibial tendonitis, which can be a long-term complication of flat feet.
  • Casting is a method used for children whose flat feet are caused by bone positional abnormalities, such as metatarsus adductus. It involves using a series of casts to assist in re-aligning leg and foot bones to their proper anatomical position.
  • Surgical procedures for flat feet vary depending on the root cause of the condition. Surgical correction to control pronation may include bone implants or Achilles tendon lengthening. Tendon transfer, which is a procedure to re-attach a tendon to another area of bone, may also be used to reduce pronation and improve foot function.


Mahan, Kieran T. MS, DPM, FACFS. (1992) Pes Planovalgus Deformity. In McGlamry, E. Dalton, DPM, Banks, Alan S. DPM, Downey, Michael S. DPM. (Eds.). Comprehensive Textbook of Foot Surgery. (2nd ed.)(pp.769-779). Baltimore: Williams & Wilkins.