Sesamoids are bones that are found in locations where a tendon passes over a joint, such as the hand, knee, and foot. They act in a functional way to protect the tendon and to increase its mechanical effect.
The sesamoids in the foot are found under the big toe and are located within the tendons that pass through this area. Sesamoiditis is when these bones become inflamed resulting in pain under the big toe joint.
Sesamoids, although less common can occur under the little toe joints and symptoms will present the same way as under the big toe.