It sounds like swelling to me. If you don't see it inside, it's still swollen inside. That inside fluid can make it really stiff and lower your bend. I understand your wanting to go ahead and get it done while your copay is covered. Ask your OS how much ROM he gets in the OR when he does the MUA. Afterwards, you will probably swell and that ROM will get worse than what he gets in the OR because of that swelling. Don't over exercise it. It needs to be treated very gently afterwards, just like you would a new tkr.