Current concepts review: septic arthritis of the knee pathophysiology, diagnostics, and therapy.

Treatments for bacterial arthritis of the knee joint are arthroscopic irrigation and debridement with systemic antibiotic medication. This article summarizes the relevant data of pathophysiology, stage of infection, symptoms, and diagnostics as well as stage-dependent treatment of bacterial arthritis of the knee joint. The major treatment principles are joint decompression, elimination of the causative organisms by intensive irrigation of the joint with elimination of proteolytic and lysosomal enzymes. Debridement of necrotic soft tissues with the aim of preserving the synovial membrane as an immune-competent structure, and a natural barrier, is recommended. Good results in treating knee infections have been achieved with arthroscopic joint revision and stage-dependent surgical therapy. The infection staging I-IV suggested by Gächter was used most commonly, which mainly reflects the pathophysiologic infection stages. For stages I-III, arthroscopic joint decompression with joint irrigation and debridement is effective and can be repeated in cases of persisting infection. The incidence of repeated arthroscopic joint irrigation depends on the initial stage of the infection and varies between 0 and 41% of the cases. For stage IV infections, the open revision is needed or in seldom cases of therapy failure under initial or repeated arthroscopic joint revision. The success rate of healing infections by arthroscopic irrigation was high with 90-100%.