Hello, I am sorry to hear that Beauty has swelling to her right ankle.
Did this seem to come up quickly?
Is she running a fever or has she even run a fever when her ankle was swollen (rectal temperature more than 103.5F)? If so have antibiotics been tried?
Is the change in the radiograph to the bones or the joint space itself? Does it seem to affect more than one bone? Does she or has she ever had more than one joint swollen?
If there is any increase in joint fluid or joint "space" an aspirate and cytology and culture of the joint fluid may be very helpful and is less invasive then a bone biopsy.
Are ticks a problem where you live? If so a tick panel may be helpful as tick borne diseases, like Lyme disease, can cause joint swelling and inflammation.
While bone cancer typically occurs in older dogs it is a cancer that can be seen at any age.
If she has never had a fever, ticks are not a problem where you live and the joint fluid aspirate and cultures (for both bacteria and fungi) come back negative a biopsy is the best way to diagnose her condition. Identifying the particular type of tumor she has, if that's what she has, is very important in prognosis and directing therapy. It is not something we do lightly but sometimes it is the only way to get a diagnosis.
Let me know if you have any further questions.