If you can, try some edibles. You might be surprised. Just do them in the evening when you aren't going anywhere, obviously lol. But, If your Doc said wait till 55 for knee replacements? BS. I had both of mine done, at the same time exactly 10 yrs ago at 46. Best life choice I could have made. You don't realize how insidious chronic pain is, until you get bilateral Knee arthroplasty and after the initial week after pain is gone, every day you wake up in a much better place because all that no cartilage knee ache is GONE. It was absolutely the best choice I could have made, at age 46.
If I were you, I'd look for a different Orthopedist if they are refusing to replace yours. Nothing worse than bone on bone with every freaking step you take.
The back, that's a tough one and I'm gonna resist surgery as long as I can. Those don't always turn out for the better.
Good luck.