What Causes Constant But Random Pain In Left Knee?

I ve had a pain in my left front side above my navel but more to the left of it. It s a dull pain that stays in the same area. Almost like a burning stabbing pain. About five years ago I had a blood clot on my left leg above my knee that wasn t a dvt. Upon completion of a gene pool test it was determined I had two mutant genes blood clotting and hard ing of the arteries. The pain is sometimes constant and then just random. I have no clue why this is random. When it hits it is tolerable but a pain to deal with. I m a male and 48 years old. Thanks