One note about arthritis. Im sure you know everything tbing there is to know about it by now but just in case...
I have been to doctors concerning my knees, the right in particular.
There have been times they hurt so bad I could barely walk. As I have gotten older it has progressed into my feet, elbows etc.
The doctor takes a look and say yep, you have arthritis, here are your options. To include knee replacement, drugs and injections. He is an excellent doctor but... never once have any of the doctors talked to me about food.
I have recently with in the past year and a half learnd that certain seemingly bland foods have been whats caused the large portion of pain. Nightshades ...potatoes and things of the like. There was I time I thought I would never be able to ride my mountain bike for more than a few miles anymore but now that I have cut those foods out I am back out there.
Your issue is more severe but perhaps it may help to some small extent to consider trying the same if you have not.