It is likely you or someone you know, be it a family member, friend, or client, has been struck down with a case of flat feet. "Flat feet" is a term used to explain anything from plantar fascia pain, Achilles injuries, shin splints, knee, hip, and back pain. In other words, almost any physical ailment between the ground and your head. So what, exactly, does flat feet mean? Is it a diagnosis? Is it terminal? And does it even exist?