Just a thought about bicycles.
A badly set up bike can be death on knees. I don't have knee probs as such, but if I wear shoes with thicker soles than usual, and cycle as little as three miles, I will be quite lame for two or three days, longer if I cycle further. For me, I need to have the seat quite high so I am not pushing down with a very bent knee.
Otherwise,
I would go for every anti-inflammatory trick known, and when the inflammation is under control, I would go for every muscle strengthening, balancing trick known. I would pay to see the best podiatrist I could find, and get biomechanics evaluated. I would get a full sports massage done, and repeat until no muscles are tight and out of balance. I would do pilates/Franklin method work to make sure that no other postural problems were aggravating the knee.
One of the things I really hated when I was on sticks was hanging around waiting for the medical community to do something for me. It made me see red when they couldn't do anything useful. Things got a lot better when I stopped waiting for them.
Some of the ideas require funding, although not in the same league as a private knee replacement, supposing you could persuade someone to do it. In an ideal world this should be on the NHS, but I'd rather do what I can and give the knee its best chance, than risk early confinement to a wheelchair because I didn't do all I could have done.
Best of luck with it.