I'm not sure this helps, but... I have patellofemoral syndrome in my right knee. My knee had pretty much hurt dully for about 6 months before I took myself to a knee doctor... The first one I saw thought that I had a tear in the knee or something and would need arthoscopic surgery and recommended an MRI. I got the MRI, there was fluid on the knee in the MRI and I went to another doctor with it.
He had me lie down and bend my leg while he was watching it and said, okay, your knee isn't tracking right because the muscles are stronger on the outside vs. the inside of your knee. That was causing the pain and the fluid.
He then prescribed physical therapy... So I went without exercising for a bit and did the physical therapy recommended exercises, they taught me how to tape my knee cap to the side so that my knee cap would track right and I was pain free by the end of that course of physical therapy.
Of course, I haven't kept up those exercises, so I still get the same type of pain and I need to do them.