Charcot Foot
This is an unusual and complicated complication of the foot in diabetes. It follows a softening of the bone a subsequent dislocation of the joints and a fracture of the bones in those who general have a nerve problem resulting in them not feeling pain. In this situation, the consequences of all this can be quite severe and difficult to treat.
This problem is becoming more common as the diabetes and obesity epidemic takes hold. This really is a medical emergency as continued weightbearing on the foot will only worsen the problem and this condition really needs to be placed in a plaster cast as soon as possible to prevent further damage (ref). There is plenty of information on the web on this condition.