Sometimes when I stand up after sitting, or sometimes just randomly, one of my knees will suddenly hurt badly. It usually goes away within a few hours but it happens many times, at least once a month. I feel the need to maybe pop my knee, but I can't do it. Am I experiencing early signs of arthritis? Do I have a joint problem? This once happened to my thumb and twice to my toe, and it goes away every time I stop moving it. Can I prevent this?