Flat feet occur when the inside arch of the foot is flattened. If you have flat feet, your whole feet touch the ground when you are standing. Flat feet are also known as;fallen arches because the arch of the foot is very mild and looks as if it has sunken or fallen. Flat feet are usually harmless and cause little or no pain, though in some cases, they can lead to problems in other parts of the leg.
Flat feet, also called pes planus or fallen arches, is a medical condition in which the arch of the foot collapses, with the entire sole of the foot coming into complete or near-complete contact with the ground.
This answer provided for NATA by the Eastern University Athletic Training Education Program.
If the middle of your foot hurts, it may reflect a change in the structural integrity of your arch. In extreme cases, arches can collapse, resulting in flat feet or fallen arches. While some people are born with fallen arches, others develop the condition over time because of weakness in the tendons and soft tissues that support the arch.
A pronated (flat) foot is one whose arch has dropped closer to the floor and contributes to the appearance of a shortened leg. An overly pronated foot can contribute to height differences between two sides of a pelvis.

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Fallen arches or flat feet result when your arches are not as curved as they should be. Most flat feet do not cause pain or other problems, however, it can cause pain in your foot and ankle, as well as swelling in these areas. You can ease the pain of fallen arches by wearing shoes with arch supports.
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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.