Pes planus, or flat feet, is a loss of the medial longitudinal arch of the foot. It can be flexible or fixed, developmental or acquired. Treatment is usually only needed if pes planus is new, painful, progressing, or associated with other problems. Non-surgical treatments include stretching exercises, orthotics, and addressing contributing factors like tight heel cords or obesity. Surgery is considered for rigid, painful pes planus or conditions that may worsen without intervention.