Flat feet is a condition in which the foot doesn't have a normal arch. It may affect one foot or both feet. Most people have a gap between in the inner side of the foot and the ground when they are standing. This is referred to as an "arch". Feet that have a low arch or no arch at all are referred to as flat feet or fallen arches. On standing the patient will have a flat arch and the foot may roll over to the inner aspect.

The symptoms vary depending on the severity of the condition. Individuals may experience corns and hard skin under the sole of the foot. The arch area may be tender and shoes will tend to wear out quickly. In severe cases the patient may experience calf, knee, hip and back pain.

Not all feet are the same
Flat feet are normal in infants and toddlers, because the foot's arch hasn't yet developed. Most people's arches develop throughout childhood, but some people never develop arches. This is a normal variation in foot type, and people without arches may or may not have problems.

Lax ligaments can cause flatfeet, as can conditions present at birth (congenital) that affect the foot.

Arches can also fall over time. Years of wear and tear can weaken the posterior tibial tendon, which runs along the inside of your ankle, from above your ankle to your arch. The posterior tibial tendon is the main support structure for the arch. An overload to this tendon can cause inflammation of the tendon (Tendonitis) and even tearing of the tendon. Once the tendon is damaged the foot's arch loses support and can flatten.

You may lose support in your arches due to:

• Ongoing stresses in your feet. One of these stresses may be long-term wearing of high heels, which can affect your Achilles tendon and change the mechanics of your ankles. Compensation by the posterior tibial tendon may eventually cause it to break down and your arches to fall.
• Obesity.
• Traumatic injury to your foot or ankle.
• Rheumatoid arthritis.
• Diabetes.

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