Extra foot bones?
The truth is, some people do have extra bones in their feet. Most of the time, one would never notice that they had these extra bones present in their feet. Usually smaller than an almond and well hidden in the depth of the foot, these small bones are called accessory ossicles (although sometimes the term sesamoid is confusingly used). These extra bones should not be confused with normal small sesamoid bones that everyone has under the big toe joint. Accessory ossicles are often round or egg shaped, and can be found under toe joints, along the sides and back of the foot, as well as around the ankle. Some people have only one, while others may have many located in either foot. There are about a dozen or so locations in which they can appear. Development of accessory ossicles occurs for a variety of reasons, none of which include cancer. For the most part, these bones are hidden and will cause no symptoms. Occasionally, these bones can be a source of pain depending on their location. For instance, when the bone sits under a toe joint, the added prominence it creates can cause a painful corn or pressure sore to develop. When located on the inside or outside of the foot along a tendon, the presence of the bone can eventually irritate the tendon and create inflammation. This is especially true if the bone sits inside the tendon, as is often the case.
The most common kinds of accessory ossicles that cause pain are found on the inside and outside edges of the foot respectively. The bone on the inside is called an os tibiale externum, while the bone found on the outside of the foot is called an os peroneum. Often hidden under or even within substance of the tendons that surround them, they can potentially be a source of tendonitis as irritation of the nearby tendon is common.
Another commonly painful accessory ossicle can be found under the big toe. Called an os interphalangeus, this bone is located under the big toe joint's 'knuckle' on the bottom of the toe. It often causes a callus to form at this location, and can occasionally be painful. In diabetics this can also cause a wound at the same site. A similar extra bone can be found under any of the other toes, although these tend to be smaller than the one under the big toe.
Yet another accessory ossicle is found behind the ankle. Called the os trigonum, this small bone can often be mistaken for a fracture on x-rays. At times, the bone can irritate a tendon that courses behind and around the ankle, and motion of the ankle can impinge on this bone, causing additional pain.
Treatment for accessory ossicles is fairly simple. If no pain is felt, then treatment is not needed. Simply leaving the bone alone will be sufficient. These extra bones generally do not cause any problems, and the body is quite comfortable with their presence. However, if pain or tendonitis eventually develops, simple steps to reduce the inflammation, like icing, anti-inflammatory medications, and foot support with a temporary brace can help. When these bones are prominent under the skin, care of any corn or callus that develops is helpful. This care can include padding or wider shoes. When pressure sores develop as a result of severe pressure, skin care and protection is vital to prevent more serious problems, such as infection. There does reach a point in which surgery may be needed to extract the extra bone. Chronic pain or pressure sores are a good indication for surgical extraction of accessory ossicles, as well as tendonitis that will not heal with non-surgical measures. When tendons are involved, the tendon will also likely need repair and support during recovery, as some incision into the body of the tendon is needed to 'shell out' the bone. The removal of an accessory ossicle usually removes all pain and re-growth of the bone does not occur.
As one can see, accessory ossicles are common in the human foot, and generally are a mere curiosity on an x-ray film. When pain does occur, they are easily removed if padding or a change in shoes does not relieve the symptoms. They are neither cancerous nor do they change the way one walks when no pain is present.
