I am having rather severe knee pain . It is especially difficult to stand up after sitting and walking down stairs. I do hear some popping noises, but faint popping. The knee feels stiff and it hurts to bend it. Do I need to see a doctor or just rest awhile. This happened after doing swim exercises after I had been vacation and not in my typical 5 day a week exercising program. I am assuming that I over -did it when getting back into my rountine. It does not appear to be swollen.