You have my sympathy, OP. I started with knee pain 10 years ago, after years of good club standard running. Arthroscopy didn’t help and I resorted to running only on level grass – lap after lap around the local school playing field – running was a drug and I needed my daily fix! Last year I had to stop doing even that as the pain became unbearable, and even walking is now painful. I have refused every offer of knee replacement, preferring to hang on to my own body parts, no-matter how decrepit! I wish you well, OP, but based on my own experience be prepared for disappointment. Having said all that, I can still cycle on fairly easy terrain, but my knees can’t handle tricky technical stuff anymore.