The first marketable hip and knee surgery robots raised high expectations. The promise was that the lifespan of an implant would be extended if a surgeon could machine the bone with high precision instead of scraping it by hand. However, the question of whether robotic intervention is beneficial or harmful to patients sparked a controversy among engineers, medical professionals, journalists, patients, and judges. Catarina Caetano da Rosa illustrates how constellations of actors have formed, leading to success in some cases and failure in others regarding surgical innovations: the attempt to transfer industrial robotic logic to human biology remained contentious.