My 80+ year old uncle has had both of his knees replaced in the last 5 years. The first one went really well, he was up and hiking around in, like, 6 weeks. The recovery on the second was a little harder, but he is fine now. He is a tough old bird from a long lived family, but still, if an 80+ year old can recover so well, I think that's a good sign. (He is a really active old guy, he goes mushroom hunting in the spring, he hikes up and down mountains in the woods and underbrush. I hope I got his genes. )