Arthritis or fractur. Sesamoiditis is painful inflammation of the sesamoid apparatus, which is located in the forefoot most patients will describe a deep achy and sharp pain in the ball of the foot behind the big toe with every step taken. It will be difficult to perform many weight bearing activities. Most patients do not have pain when at rest. Could be treated by consevatie means. Or surgical means.
Sesamoids. Are little bones that are invested in a tendon, which act as a fulcrum to make the tendon more efficient. In the foot, two are typically found under the 1st metatarsal head and they add strength to the flexor tendons to your big toe. Because sesamoids do not have a periosteum (covering like other bones have), when injured or fractured, they can take a long time to heal and sometimes never heal.