Sesamoids are small bones that are connected only to tendons or are embedded in muscle. This structure appears in only a few places in the human body, one of which is the foot. Two very small sesamoids (about the size of a kernel of corn) are found in the underside of the forefoot near the big toe—one on the outer side of the foot and the other closer to the middle of the foot. Sesamoids provide a smooth surface over which the tendons slide, thus increasing the ability of the tendons to transmit muscle forces. In the foot, sesamoids assist with weight-bearing and help elevate the bones of the big toe.
Like other bones, sesamoids can fracture. Additionally, the tendons surrounding the sesamoids can become irritated or inflamed, which is called sesamoiditis and is a form of tendonitis. Sesamoiditis is a common condition among ballet dancers, runners, and baseball catchers because of the pressures placed on their feet.
Surgery is usually not required to treat sesamoiditis. Treatments generally include:
If symptoms persist, you may need to wear a removable brace on the leg for four-to-six weeks to give the inflammation time to subside and the bones to heal.