Don't always reveal fractures. The fracture of my calcaneous (earlier this summer) didn't show in a foot x-ray, but was clear as day in a c-t scan. The fracture of my humerus (2 weeks ago) didn't show in a shoulder x-ray, but an ultrasound located a small fragment that had pulled off. So, be nice to your ankle and be patient :-).
Also there's evidently some skill involved in reading them. The doc who examined my son's wrist this summer took an x-ray and pronounced it sprained but not broken. After a couple weeks passed with no improvement I took him to an orthopedic specialty place, with the original x-ray in hand, and the doc there was able to locate the hairline fracture the 1st guy didn't see. And to top it off, it was in the exact bone I told the 1st guy to check!
I had the same experience with my toe two years ago. Orthopedic surgeon missed the fracture on the x-ray, said it would just heal, then after six months I had someone else read it, found the fracture right in the joint.