flat foot, condition of the human foot in which the entire sole rests on the ground when the person is standing. When the foot muscles are weakened or the ligaments are strained and stretched, the arch lowers, so that instead of the natural curved contour, there is flattening of the entire sole. Sometimes no discomfort accompanies flat foot. However, fallen arches may cause disalignment of other foot structures so that there is pain not only in the arch area but also in the calf muscles and sometimes as far up as the lower back; the discomfort is increased by prolonged standing. Flat foot may be inherited or may be caused by rickets, obesity, metabolic disorder, debilitating disease, or faulty footwear. Treatment and exercise directed by an orthopedic physician are sometimes advisable. Arch supports or other devices to be worn inside the shoe are often prescribed.
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