I had this a few years ago. It got to the point where I was worried going up ladders (like into the loft) because the knees had a habit of giving way.
I wasn't doing much cycling at that point (before I was a born-again cyclist). I went to the doc, crossed my legs, she put her hand on my knee as I straightened it. She said "Ewww, I'm not doing that again" and sent me of to the hospital. Lots of x-rays, they suggested keyhole scale'n'polish, but also suggested leaving it until it was at a point where potential side effects would not be as bad as living with it.
I took a lot of vitamin-i as they recommended, and didn't bother with the knife.
When I started cycling again I had to be careful which leg I started off with, and to not push to hard on starting as that would cause huge pain. But it has gradually got better over the years, so now I hardly have any problems - certainly my knees are no worse than other ageing parts of my body! I regularly take other joint-related pills (cod liver oil, Glucosamine and chondroitin sulphate) which I started using after getting a thumb injury in a car accident. They seem to have helped too - but I don't remember if you are veggie so they may not be appropriate for you.
Hope you get sorted.