Flat foot is a medical condition where the arch of the foot completely collapses.  Flat foot is caused by injury, extreme prolonged stress on the foot, normal aging process and pregnancy.  If the patient stands on their toes, or pulls their toes back and an arch appears; it’s called flexible flat feet.  This means the foot is supple and the heel cord isn’t tight.  Rigid Flat feet is when the foot is completely flat in all positions with a tight heel cord; meaning the foot cannot bend back more then 15 degrees.  Rigid flat feet causes pain and calluses.