Flat feet (also calle pes planus or fallen arches) is an informal reference to a medical 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). It should be noted that being flatfooted does not decrease footspeed; having flat feet does not affect one's response to the Plantar reflex test; and horses also develop flat feet.