I am sorry you are going through this. I have had the same problem. I started having trouble with my knees and jaw at age 15. I am now 34, and my symptoms have not gone away, but gotten worse. I still don't know what it is that is causing it.
At first, they told me growing pains, then chondromalacia patella (is that how you spell it?). I was told to do exercises to strengthen my thigh muscles, but it didn't work. Then later on I started to have severe inflammation, with warmth and redness... and my GP thought for sure I had RA. I had been tested for the rheumatoid factor, but never tested positive. When I was tested during a flare, it did show up weak positive, but then went back to being negative.
I went to see a specialist and he said I couldn't have RA because my toe joints and finger joints were not involved and after all these years of problems, I had no bone erosion. OA was ruled out.
That was last year. I left his office still wondering what it is. He said he suspected serositis in my lungs and the year before had sent me to get a chest x-ray, which showed up nothing...but he said he wasn't ruling it out. That was the last I heard from anyone. A year ago.
My GP told me that if I experience anything again, to go see him asap. So at least I know he is concerned. I am going to see him next Tuesday.
All this, in my long winded way, to say I know what you are going through. Two years is nothing, but I know it is two years too long for anyone! Like I said before, I am so sorry you are going through this. Don't do what I do. I leave it go. My thyroid is not working now because of the flares and not being treated. You need to stay on this until you get some answers. Because, if you don't, your symptoms could get worse.