I assume that amputation/chemo is a serious alternative, so what I have to say is going to be unhelpful at best, but...
I have ruled out amputation/chemo in all cases to date. When the diagnosis has not been clear, we have sometimes treated for a possible bone infection with Clindamycin. We've also repeated the x-rays, although the interval has varied depending on symptoms and the nature of the original x-ray. As Burpdog says, after losing a few to osteo, you get to know even when the x-rays lie. (I've also been wrong--I thought Pink was finished over a year ago. She's still here.)