Post-traumatic plasminogenesis in intraarticular exudate in the knee joint.

BACKGROUND: Intraarticular exudate, observed in the knee joint a few weeks after a traumatic incident, is one of post-traumatic complications. Evacuation of the exudate prevents damage of the articular cartilage by the fluid possessing potent proteolytic properties. In view of the lack of data concerning the role of the fibrinolysis system in proteolytic destructive processes induced by the exudate, the aim of the study was to find out whether plasmin is present in the post-traumatic intraarticular exudate and whether it is generated in connection with excessive plasminogen activator levels or deficiency of plasminogen activator inhibitors in the synovial fluid. MATERIAL/
METHODS: 55 patients (mean age 35.1), with history of knee joint traumas and exudate appearing in the joint at least 3 weeks post-traumatically. The patients and 30 healthy controls were subjected to the following tests of the synovial fluid and plasma: the levels of tissue plasminogen activator, type 1 plasminogen activator inhibitor, plasmin-alpha 2-antiplasmin complexes, fibrinogen and von Willebrand factor antigen, the activity of urokinase plasminogen activator, prekallikrein, alpha-2-antiplasmin, C1 inhibitor, type 1 plasminogen activator inhibitor, euglobulin clot lysis time.
RESULTS: The patients' plasma demonstrated significantly higher levels of fibrinogen and PAP complexes, and decreased u-PA activity in comparison in that obtained from the controls. Significantly higher levels of PAP complexes and u-PA antigen were found in the exudate than in the patients' plasma.
CONCLUSIONS: Local, intraarticular plasmin generation, probably u-PA-dependent, occurs in knee joint exudate. Plasminogen activator inhibitors are probably not very closely associated with increased intraarticular plasminogenesis.