Flat foot, sometimes called pes planus, refers to a foot shape in which the arch appears low or absent when standing. In some individuals, the entire sole of the foot makes contact with the ground, while in others the arch is visible only when sitting or on tiptoe.

Normal Foot Development

During early childhood it is common for the feet to appear flat because the arch has not yet fully developed and because of the natural flexibility of young tissues. A soft pad of fat on the inner side of the foot can also make the arch look lower. As children grow, the bones, ligaments, and muscles of the foot typically strengthen, and a clearer arch often becomes visible.

Flat foot can have several causes, including inherited patterns of foot structure, ligament laxity, neuromuscular conditions, previous injury, or arthritis in adulthood. Some people have flexible flat feet that cause little or no discomfort, while others may develop pain, fatigue, or problems with prolonged standing or walking. Evaluation by a qualified professional can help determine whether treatment, such as exercises, footwear changes, or other measures, is appropriate.