Abstract
Infection is one of the most feared complications in the postoperative period of knee arthroplasties. With the progressive aging of the population and the increased incidence of degenerative joint diseases, there is an exponential increase in the number of arthroplasties performed and, consequently, in the number of postoperative infections. The diagnosis of these should follow a hierarchical protocol, with well-defined criteria, which lead to diagnostic conclusion, thus guiding the most appropriate treatment. The aim of the present update article is to present the main risk factors, classifications and, mainly, to guide diagnostic investigation in an organized manner.