advice wanted

We are struggling with or 11 year old labs front leg.  It is very swollen and all she does is lay around. X ray is not clear as to whether it is arthritis or osteosarcoma.  Her blood panel and lung stay came back good. We are on pain meds and antiinflammatories and watching for improvement to try and rule out osteosarcoma.  We can’t really afford many more test so a bobe biopsy is really not an option.  We are prepared to amputate if necessary. Anyone have any experience with trying these meds to see if it’s arthritis before you amputate.  I am open for suggestions.  She is in good health besides her right front leg.  .I am not ready to lose her yet