You need to discuss this with the surgeon who did this for you. Call him or her up and ask about the swelling. You may have swelling and warmth about the knee persistently for 6 weeks after surgery. This will gradually decrease, but it may take 6 months to a year for the swelling to resolve completely. It just depends on how easy or complicated the operation went, how your body reacted to it, and so on. There are a lot of factors, but it is always best to discuss any concerns you have with your doctor to make sure everything is going well.