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

Abstract

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%.

Posterior Knee Dislocation Following Septic Arthritis of the Knee

“…6 Staphylococcus aureus in particular has also been shown to release lysosomal enzymes to surrounding tissues within hours of inoculation, hastening destruction of cartilage and surrounding tissue. 6 Following inoculation, 4 stages of joint infection were described by Gäechter from observations during athroscopic treatment. 7 First opacity of the synovial fluid develops along with redness and possible petechial bleeding of the synovial membrane.…”

“…The decision for initial approach using arthroscopic techniques was made due to the fact that it had been an effective treatment option in previous cases at this institution and has also shown to be a preferred treatment option in the orthopedic literature. 6,7 The exact mechanism of a knee dislocation following septic arthritis of the knee is unknown. However, we hypothesize that the soft tissues including the cruciate and collateral ligaments were made incompetent by digestion by enzymes from both the pathogenic organism and from the host immune cells and subsequent stretching with mobilization allowed the knee to dislocate without a traumatic event.…”

“…5 It has been determined that corticosteroid injection, as this patient had undergone, carries an infection rate 6 of 0.1%. This patient may have been inoculated with his injections and placed at further risk of bacterial proliferation due to his immunocompromised state secondary to sarcoidosis.…”

“…Once the joint is inoculated, bacterial virulence factors and the immune response incite inflammatory changes to the surround tissues. 6 This includes the recruitment of polymorphonuclear leukocytes which release proteolytic enzymes that are destructive to both the pathogen and the host tissue. 6 Staphylococcus aureus in particular has also been shown to release lysosomal enzymes to surrounding tissues within hours of inoculation, hastening destruction of cartilage and surrounding tissue.…”

“…6 This includes the recruitment of polymorphonuclear leukocytes which release proteolytic enzymes that are destructive to both the pathogen and the host tissue. 6 Staphylococcus aureus in particular has also been shown to release lysosomal enzymes to surrounding tissues within hours of inoculation, hastening destruction of cartilage and surrounding tissue. 6 Following inoculation, 4 stages of joint infection were described by Gäechter from observations during athroscopic treatment.…”