Infected native knee joint: Diagnostics and treatment regimen

A knee joint infection is considered a surgical emergency, which if left untreated can lead to irreversible joint destruction and poor functional outcome. Etiologically, a distinction is made between endogenous and exogenous causes as well as early and late infections. The general incidence is low but increases with the proportion of implanted foreign material. Bacterial infection and the associated release of the body’s own cytokines and lysosomal proteins already leads to cartilage damage within 48 h. The combination of clinical, histopathological and microbiological results flanked by laboratory values and imaging leads to the diagnosis. Treatment includes the surgical cleansing of the infection combined with administration of antibiotics. Infections of a previously healthy knee joint are treated arthroscopically, whereby a one-stage intervention is usually sufficient. An infection after cruciate ligament transplantation is also treated arthroscopically and not uncommonly by a multistage procedure. The transplants can be preserved if they are intraoperatively stable. The treatment of choice for peri-implant infections with consolidated fractures is arthroscopic debridement and implant removal. In cases of nonconsolidated fractures and early infections, preservation of osteosynthesis can be achieved by performing revision surgery; however, a late infection usually requires a two-stage procedure. The initially calculated antibiotic treatment is adjusted accordingly when the antibiogram and resistogram are completed. The duration of antibiotic treatment varies from 6 weeks for an infection of a previously healthy knee to 12 weeks for a peri-implant infection.