Our bodies are already pretty much cobbled together by evolution, our feet were more like our hands in the distant past where they could grip stuff more readily but as we became bipedal that gradually changed and they became more rigid, our knees do what they can for us, but mammal knees aren't really meant to hold the entire weight and if you want to see some good bipedal knees, look at dinosaurs that had millions of years to get past that. Same with our spine, it's all cobbled together and then as we age we start to develop more issues in this hotspots where on a fundamental level our bodies aren't well designed, this kind of surgery is like looking at all of that and saying you want it to be worse. Can't imagine what these people will be like when they're elders and this kind of stuff really will bite them in the ass.