The sesamoids are two small bones underneath the big toe joints about the size of peas. They for a joint with the big toe joint and are a site of attachment for tendons. They can get injured either as a direct injury (e.g. landing form a jump) and can even fracture, or can cause problems as an overuse injury (e.g. repetitive trauma from distance running). Pivoting sports place a lot of strain on the area and are a common cause of sesamoid problems.
You will experience pain when you put weight through the ball of the foot and it may be more comfortable to walk on the outside edge of the foot. It may settle during activity if it is an inflammatory pain, or may get progressively worse if it is a stress fracture.
Despite being tiny bones these injuries can cause big problems so should be taken seriously and treated early.
If you think you have this condition it is well worth getting it checked as soon as possible by Mr Willis-Owen. You should avoid any aggravating activities with may make things worse. It will not get better on its own, and needs to be treated properly as soon as possible. If you try to ignore it, it may have serious long term effects.
Management involves first confirming the diagnosis which is not particularly easy. Special X-rays, CT scans, MRI scanning or bone scanning may be needed. Treatment includes plaster casts, orthotics, physio, injections and surgery. It is an injury that is best dealt with early.