"Knee replacement is bound to fail-providing the patient lives long enough." There is some truth in this hoary cliche, so why write books on the subject? I think the answer is that knee replacement has at last become established and even respectable. The more absurd surgical extravaganzas have been recognised and discarded; today a patient can expect to rely on his new knee to serve him with comfort for a fair number of years. Of course even the early knee replacements often made the patient comfortable; the trouble was they just did not last. All too often the innovator's enthusiasm was overtaken by the patient's disillusionment. Indeed, the operation might well have been abandoned had it not been for the hope that one day the dazzling results at the hip might be matched at the knee. These pioneer prostheses were designed as though the knee were biomechanically as straightforward as the hip. Alas, numerous complexities soon became apparent; in response the models multiplied-and multiplied-until the ordinary orthopaedic practitioner became hopelessly bewildered. He found himself subjected to high pressure propaganda; from the surgeon offering a miracle cure, from the engineer seeking fame and from the manufacturer expecting fortune. Visiting his unit as a team, this trio was well-nigh irresistible.