The main joint of your big toe forms the inside edge of the ball of your foot. On the underside of this joint are located two pea-sized bones that are embedded within the soft tissue of your foot. These are called sesamoid bones.. There is one sesamoid bone on each side of the base of your big toe.
When you bend your big toe down (using your toe flexors), these muscles pass underneath the big toe, crossing over the bump created by the sesamoid bones. These sesamoids act as a fulcrum point for your big toe, allowing your toe flexor muscles leverage. The sesamoids also help to absorb pressure under your foot while you stand or walk and they ease friction in the soft tissues under your toe joint when you move your big toe.
There are a few bones in the human body that are connected only to tendons or are embedded in muscle. These are the sesamoids. Two very small sesamoids (about the size of a kernel of corn) are found in the underside of your forefoot near the great toe - one on the outer side of your foot and the other closer to the middle of your foot.
Sesamoids provide a smooth surface over which the tendons slide, thus increasing the ability of your tendons to transmit muscle forces. The sesamoids in the forefoot also assist with weight-bearing and help elevate the bones of the great toe. Like other bones, sesamoids can fracture. Additionally, the tendons surrounding the sesamoids can become irritated or inflamed. This is called sesamoiditis and is a form of tendonitis, and is common among ballet dancers, runners and baseball catchers.
You will feel pain under your big toe or on the ball of your foot, swelling and bruising or difficulty and pain in bending and straightening your big toe.
Dr. Fosdick can prescribe pain relief, orthotics and, if the condition is very severe, may suggest surgery to make your feet feel better.