I have a form of arthritis that is not only a whole bunch of fun (

) but has rendered my right knee pretty unusable. A knee replacement is definitely something that will happen sometime, but my orthopaedic surgeon tells me that I am quite young for knee replacement (at least I'm too young for something!), and that if I had a knee replacement done now, I might have to have a whole new procedure done when I am in my 70s or 80s.
Anybody out there had knee replacement done in your 40s or 50s? Were you told the same thing? Have you any input for me?