This week my knee has been really sore.....stiff. It hurts when I keep it in the same position for a long period of time. For example like driving to work 40 mins. When I walk around on it there really is no pain. I just did heavy squats (which never bothered me) then I did something new throwing in some lunges also. Would lunges effect the knees a lot? normally on my squats I only go parallel and they never bother me.