Sesamoiditis is an inflammatory condition that involves the sesamoid bones. These two small, egg-shaped bones about the size of a peanut M&M candy sit under the big toe joint. They fit within two shallow grooves formed on the bottom of the first metatarsal head, the long bone that forms the first part of that joint. The sesamoid bones take an incredible amount of pressure, stress, and force with every step one takes. This puts these bones at risk for developing injury and inflammation as a response to these forces. The sesamoids are rarely both injured at the same time, and it is more common for the sesamoid closest to the side of the foot to become inflamed. The sesamoids are injured by numerous events, including falling from a height onto the ball of the foot, repetitive pressure on the ball of the foot from activities such as dancing or stair climber use, or even indirectly from abnormal pulling of the tissue that attaches near or on the sesamoids.

Symptoms will include a sharp pain or dull ache on the bottom of the big toe joint that is worsened when the joint is flexed upwards. Walking, running, and jumping can be painful with this condition, especially while barefoot. Shoe use tends to decrease the pain somewhat, although high heeled-shoes make it worse. The area under the big toe joint can feel puffy, and may even be warm to the touch in less common cases. Sesamoiditis is typically diagnosed by the symptoms and a physical exam, although x-rays are usually taken to ensure the sesamoids are not fractured. Stress fractures of the sesamoids can mimic the symptoms of sesamoiditis, and may not show up early on the x-ray. Special imaging like an MRI or nuclear bone scan is performed to confirm a stress fracture, and treatment takes longer than that of sesamoiditis.

Treatment of sesamoiditis itself involves removing the inflammation, and reducing the stress that caused it in the first place. Inflammation can be relieved by anti-inflammatory medications, as well as icing. If no fracture or stress fracture is suspected, a steroid injection can be given to reduce the inflammatory reaction of the bone and its surrounding region. The stress is reduced by using padding or inserts to reduce pressure under the ball of the foot, or by modifying the activity that caused it in the first place. More serious cases may require immobilization in a walking boot or in a cast for up to several months, and surgical removal is needed in cases that simply won't heal. Most people recover uneventfully and don't need surgery or prolonged immobilization. Dancers and athletes can return to activity once the condition resolves, but with the knowledge the condition may return if stress to the big toe joint continues.