Not Yet. I'll be getting my left knee replaced in early '13.
I do have a BAD back. I've had 3 spine surgury's & have a
metal plate in my neck & rods & screws in my back & ride
every chance I get with the only problem being stiffness after
a while in the saddle. Good Luck when you get it done..
They've come a long way in the last couple years. My grandpa had his hip replaced last year and it doesn't affect him one bit, he does everything he used to do. He can sit on his tractor all day, he jogs, he and I go hiking together alot, you name it. I don't think you'd have any problems riding with a new hip, at least if it turns out as well as it did with my grandpa!
"8 But God demonstrates his own love for us in this: While we were still sinners, Christ died for us."