I'm glad they're checking on the lumps. Poor Fizzy. In my experience, Tramadol is one of the safer pain meds. I'm also just going to toss this out there, so please don't think I'm insane - Turmeric. Yes, the kitchen spice. It's good for inflammation. A google search will bring up a lot of info on it. I've used it not for arthritis, but a different type of inflammation in one of my boxers and it helped a lot. It should be safe to use in conjunction with Tramadol.
Just for long term thinking, somewhere I have a picture of a sling on a moving bar attached to the ceiling that my friend built for his boy with DM so that he could eat by himself at his raised food dishes. He had a lot of tricks that helped Zack live a fairly active life for several years longer than the vets predicted. If there's any information that you need I'd be happy to get in contact with him at any time. My DM boy's heart gave out before the DM really affected him, so I don't have that much experience. Gentle hugs to Fizzy.