The infection of a total knee replacement often imposes changing implants. The change in two step is currently considered the gold standard. The change in one step is a much debated attitude: strictly contra-indicated for some professionals, but others agree to reserve these for favorable suspected cases selected. Several criteria have been proposed in the literature: age, condition, duration of infection, known bacterium responsible, not virulent and sensitive to antibiotics, no fistula, no significant bone destruction. But these criteria are poorly validated, standing over an experience of surgical teams rather than high-level scientific studies. Some authors have proposed to achieve change in one step systematically. The results of these cohorts on healing the infection does not seem very different from the changes in two steps. But it is most often single-center series, uncontrolled, with small numbers.