A flat foot is when the plantar arch is completely collapsed. Usually hereditary in nature, this foot type can be problematic in the short and long term. It may be responsible for pain in the knees, hips and lower back as well as muscle fatigue of the feet and legs due to constant overuse.
"False" flat feet are feet that have an arch when non-weight bearing, but collapse when standing. This type of foot can cause the same symptoms and problems as "true" flat feet. Carefully prescribed orthotics can relieve symptoms by improving the alignment and posture of the foot.