Intermittent Knee Bursitis

Hello all. This is a problem I' ve had for about 3 years now . Sometimes it goes completely away but anymore , it's always around. For awhile it would seemingly bounce from knee to knee but now it seems to stay in my left knee . I can walk and stand fine but can't take my occasional light jog any longer . I used to be able to sit anyplace by folding my legs up underneath me on the floor like people do when they're outside at a park for instance ,but now the left leg is entirely too stiff to be bent all the way like that . Sometimes it seems to go completely away though . Any ideas folks? I'm 42 and generally in good health and try to watch what I eat and am thin but muscular. I juice raw fruits and veggies 2 or 3 times a week and hardly ever eat fried food or fast food . I also use Braggs organic apple cider vinegar and take either Carlson's fish oil or Barleans Omega man oil . Thanks !