My doctor says I have osteoarthritis in my knee. He gave me a cortisone shot, which lasted almost a year. I am an active person and exercise often, so he tried a series of shots (3) of lubricant, which ended about two weeks ago. My knee had a lot of swelling, which has subsided, but it is still painful when I stoop down, etc. This weekend it started making a noticeably loud crackling noise - a staccato click - when I descend the stairs or stoop. It doesn't happen when I go up the stairs. Please, what is this? I'm frustrated.