A sesamoid is a bone that is inside of a tendon. There are two sesamoid bones found under the foot near the big toe joint. These bones can become injured and inflamed. When this occurs, it is called sesamoiditis.
Typically sesamoiditis occurs as a result of an overuse injury. Repetitive, high impact activities can inflict this type of injury and can result in pain under the ball of the foot, near the big toe joint.
After taking a thorough history, your specialist will evaluate foot with emphasis around the big toe joint. X-rays are usually ordered as a part of the workup. Advanced imaging studies (ex. Ultrasound or MRI) may be ordered, particularly in chronic, longstanding cases.