I have been having feelings of tightness and sharp spasms of pain in my left knee. The pain varies in intensity and comes and goes. I've noticed it only occasionally before, but in the past week it has become more severe and almost constant. It seems to feel the worst when I am in bed and changing positions. I have never had an injury to the leg or anything like that. In fact, I am not athletic at all. I have an extensive family history of osteoarthritis, but this seems unlikely as I am only 23-years-old. I am wondering if my lack of much physical activity could be the cause of the pain?