Sesamoiditis is a condition that causes pain in the sesamoid bones, which are two small bones located under the big toe joint. It is a common problem in runners and other athletes who put a lot of pressure on their feet. Symptoms of sesamoiditis include pain under the big toe joint, swelling, and bruising. The pain may be worse when you walk or run. Treatment for sesamoiditis typically involves rest, ice, and elevation. You may also need to wear a splint or shoe insert to help reduce pressure on the sesamoid bones. In some cases, surgery may be necessary to remove the sesamoid bones. If you have pain under your big toe joint, it is important to see a doctor to get a diagnosis and treatment plan.