My Dad at 87 had both knees replaced. He was out of bed the next day and walking (with a great deal of pain) within two days. His projected ten day hospital stay was reduced to six. His 14 day nursing home stay for therapy was reduced to 4. The secret - grit your teeth and go for it. He will be 89 this August and walks around pain free. Before the surgery, he could barely walk at all, could not climb stairs or even walk up a curb.

I suppose a lot depends on your threshhold for pain. But why spend your twenties suffering?