Platfus to inaczej płaskostopie, które polega na nadmiernym obniżeniu się łuku podłużnego i/lub poprzecznego stopy. Widocznym objawem płaskostopia podłużnego jest wypłaszczenie sklepienia od przyśrodkowej strony stopy oraz nadmierne pochylenie pięty do środka (koślawość tyłostopia). Płaskostopiu poprzecznemu towarzyszy tworzenie się bolesnych modzeli i odgniotów na podeszwie z przodu stopy, poszerzenie przodostopia oraz zniekształcenia palców: haluksy, palce młotkowate lub szponiaste.

In the course of flat feet, the foot loses the ability to absorb shocks and to effectively bounce off the big toe. This leads to overloading the muscles and joints of the foot and disturbs the biomechanics of the higher parts of the body (knees, hips, spine). Flat feet may be accompanied by deformation of the foot and toes, making footwear selection difficult. The main problem of symptomatic flatfoot, however, is pain in damaged tissues, which makes it difficult to walk and worsens the quality of life.

Physiological flat feet in children and mild corrective forms of flat feet in adults do not cause pain. Pain from flat feet may occur when a person with flat feet is competing in sports (e.g., jogging), is overweight or spends the entire day standing. In such cases, muscles and joints may be overloaded, micro-injuries accumulate and pain may be triggered. Foot pain in advanced and permanent flat feet results most often from degenerative changes in joints and pathological stresses of soft tissues (ligaments, plantar fascia and muscle tendons).