Sesamoid fractures occur when there is either a forceful injury to the area under the great toe joint, or when there is a repetitive microtrauma to that area, such as during continued jumping or foot pounding. The sesamoids are two small egg-shaped bones found underneath the great toe joint. They are a normal part of human anatomy, and sometimes one or both can be found in two pieces if they do not fully fuse during the bone growth phase in childhood. They have a specific stabilizing function during walking and standing, and can be a source of great pain when injured.

The sesamoid bones can fracture into two or more pieces under a number of conditions. Direct trauma to the sesamoid, such as during a fall from a height onto the ball of the foot or from a heavy blunt object smashing into the sole of the foot, can cause the bone to break. Trauma that also forces the great toe upward suddenly also can cause the bones to shear apart.

Stress fractures, in which the bone is not completely broken but is microscopically damaged and cracked, can occur when there is a constant source of stress or excessive loading on the bone. This can occur in sporting situations in which there is frequent jumping, as well as in occupational situations such as when one has to leap off of platforms or from a height frequently. The damaged bone is essentially fractured from within, and eventually may convert to a full fracture if the stress continues.

Sesamoid fractures are healed for the most part by immobilizing the foot in a walking boot or cast to limit great toe motion and pressure to the ball of the foot. The healing process may take longer than other bones in the foot, at least partly owing to the more limited blood supply the sesamoids have. A healing time of eight weeks is not uncommon. Stress fractures may take even longer to heal. In certain situations, such as when the fractures are not healing or when the fracture obliterates the bone into many small pieces, the bone must be removed to relieve the pain. Called a sesamoidectomy, this procedure involves complete removal of the fractured sesamoid. Sometimes this removal can affect the position and stability of the great toe to some degree, but the risk is often necessary to relieve pain when nothing else will.