Fallen arches, also called flat feet or pes planus, is a condition in which the entire bottom of the foot touches the ground when one is standing. A normal foot has an arch between the heel and the ball of the foot. Fallen arches are typically an acquired condition, though flat feet may be present from childhood if the arch never developed in the first place. In some cases, usually those in which the arch never developed, flat feet are not a cause for concern. However, if fallen arches develop in adulthood, causing a rigid flat foot, the condition is usually accompanied by pain and can cause serious health issues.

Rigid fallen arches are usually easy to distinguish from the flexible variety from the pain, but there is a simple test you can perform if you are not sure. Stand on the toes, and if the arch appears, your condition is known as flexible flat foot and is nothing to worry about. There have been Olympic runners with flat feet of this kind. On the other hand, if your foot remains flat on the bottom when you stand on your toes, you have rigid fallen arches and should consult a podiatrist; likewise if you notice any change in the arches of your feet. If you are experiencing any foot pain, you should also consult a podiatrist, whether or not this test suggests you have flexible flat feet.

Fallen arches may result from a number of causes, including increased elastin during pregnancy, arthritis, injury, excessive stress on the foot, fused bones in the foot, or an extra bone. Rigid fallen arches may cause not only foot pain, but also pain in the legs, knees, and back and a loss of mobility. The condition is most often treated with orthotics, structures placed in the shoes to support the feet, but this may not be sufficient for severe cases. Exercises to strengthen and rebuild the arches can also be helpful. Surgery is sometimes the best method, as it can completely rebuild fallen arches and has lasting results, but it is quite expensive and considered a last resort.