Elon Musk says that within a few years robots will perform all of our surgery — and do it better than any human surgeon alive. As a surgeon who uses computer-assisted navigation in his own operating room, Dr. Schultz explains exactly why that's wrong: the part today's surgical robots actually handle is one of the easiest steps of a knee replacement — the bone cuts we trust to a first-year resident — while the hard part is everything the technology can't see.