Flat Feet - Flat feet, also called pes planus or fallen arches, is a 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. In some individuals (an estimated 20-30% of the general population) the arch simply never develops in one foot (unilaterally) or both feet (bilaterally)
Pronation of the Foot - The pronated foot is one in which the heel bone angles inward and the arch tends to collapse. A "knock-kneed" person has overly pronated feet. This flattens the arch as the foot strikes the ground in order to absorb shock when the heel hits the ground, and to assist in balance during mid-stance. If habits develop, this action can lead to foot pain as well as knee pain, shin splints, achilles tendonitits and plantar fasciitis.