Most likely you are having symptoms of osteoarthritis? What is your age? Is the symptoms have been more prominent in the morning, when you put your first step out to work? Take an X ray and if symptoms mimic osteoarthritis then take some pain killers like ibuprofen and glucosamine for better joint lubrication.
I am 65... and yes I have Osteoarthrits... I am really sure that having a knee replaced will not make easy to stand for any lenght of time.. or get up from a sitting position...
I hope I have made this problem clear... I just feel my body has to many problems based on the weight... to have a knee replacement help at this point....
I have two knee replacement done one was done on April 26 / 2011 and the other was done on may 21/ 2013 not too long ago but my legs are in pain the back off my legs sometimes I can't sleep at all because off the pain sometimes their swallowed in both legs what can you says to me ca you help me