they have improved the surg and the replacement part these days.... I have a friend that had the total knee replacement last year and he is riding ATV/horses, snow sking and just about anything he wants.. the new procedures make the surg much easier to get over it post op.....
Same for the Hip... SIL had it done and she wishes she had done it sooner!!!! she walks, ski and everthing without pain!
I say go for it....