Ankle pain

For a few years now I've had problems with my ankles being fine one day then unable to walk on them the next. ...The pain normally starts around the ankle area then works towards the toes top and bottom and can last from 3 day so to 2 weeks, sometimes I can hobble through this and others I need crutches just to get to the bathroom. It can also stop in one foot and start in the other overnight, Doctors don't seem to have any ideas as X rays and other tests show all is fine....can anyone else relate to this and possibly offer a name for it and any possible treatments please. Regards Richard