What Causes Flat Feet?

Q. What causes flat feet in adults?

A. Flat feet—also called flatfoot, or fallen arches—can develop in adults for a number of reasons, including aging. Wear and tear can weaken the posterior tibial tendon, which helps support the arch, resulting in an instep that touches the ground when you stand. An injury can damage the posterior tibial tendon or the foot’s ligaments and small bones, causing the arch to fall. Another cause of flat feet—pes planus in medical terms—is arthritis, which can wreak havoc on the foot’s joint cartilage and ligaments. Conditions such as obesity and diabetes can increase your risk of flat feet.

Many people have flat feet, but not everyone has symptoms, which may include pain along the inside of the foot and ankle, pain that worsens with activity, or pressure or swelling on the ankle or bottom of the foot. Treatment can include rest, physical therapy, weight loss, drug therapy, a walking boot or cast, an over-the-counter or custom-made orthotic shoe insert for arch support, or a special foot brace worn periodically. If none of these treatments work, your doctor may suggest surgery to realign the foot and relieve your pain, but recovery could take up to a year.

Reviewed by Thomas N. Joseph, M.D., an orthopedic surgeon at Freedom Orthopedic and Rehab in Atlanta.