Clinical correlation with the PA/plasmin system in septic arthritis of the knee.

Abstract

Substantially more gelatinases appear in effusions of septic arthritis than in effusions of aseptic arthritis. We hypothesized there is greater plasminogen activator/plasmin activity in effusions of septic arthritis than aseptic arthritis. We examined the antigenic values of urokinase-type plasminogen activator and plasminogen activator inhibitor Type-1, cell counts, and levels of matrix metalloproteinase-2 and metalloproteinase-9 in 135 knee effusions from 80 patients with septic arthritis, rheumatoid arthritis, gouty arthritis, and osteoarthritis. Urokinase-type plasminogen activator and plasminogen activator inhibitor Type-1 antigenic values in effusions of septic arthritis were greater than those in effusions of aseptic arthritis. The increases of urokinase-type plasminogen activator and plasminogen activator inhibitor Type-1 antigenic values in effusions were associated with increased levels of prometalloproteinase-9 and the appearance of activated metalloproteinase-2. Antigenic values of urokinase-type plasminogen activator also correlated with the appearance of activated metalloproteinase-9. High plasminogen activator/plasmin activity, prometalloproteinase-9 levels, and the presence of activated metalloproteinase-2 and metalloproteinase-9 in effusions from replaced knees should increase suspicion of infection regardless of neutrophil counts. Joint aspiration reduces bacteria counts, endotoxins, proinflammatory cytokines, and matrix metalloproteinase. It also decreases the plasminogen activator/plasmin activity in effusions that may play a part in extracellular matrix destruction. Diagnostic study, Level III (study of nonconsecutive patients without consistently applied reference "gold" standard). See the Guidelines for Authors for a complete description of levels of evidence.