Association between degree of bone-erosion and synovial fluid-levels of tumor necrosis factor alpha in the knee-joints of patients with rheumatoid arthritis.

OBJECTIVE: To determine whether concentrations of cytokines and matrix-degrading enzymes in synovial fluid of patients with rheumatoid arthritis or osteoarthritis are associated with the degree of bone-destruction in the same joint.
METHODS: Determination of Interleukin-1 alpha, IL-1 beta, IL-1-receptor-antagonist, IL-6, IL-8, tumor necrosis factor alpha (by ELISA), collagenase-activity and caseinase-activity (by substrate-assays) in the SF (knee) of patients with RA (n42) or OA (n35). The degree of bone-destruction was assessed radiographically.
RESULTS: SF cytokine- and enzyme-levels were higher in patients with RA than in those with OA. In the RA group, SF-levels of TNF alpha were positively correlated with the degree of bone destruction of the respective joint. No correlation was found between radiographically assessed joint changes and SF-concentrations of other cytokines, enzyme activities, serum CRP, or duration of disease. In the OA-group, none of the examined parameters was associated with the degree of joint destruction.
CONCLUSIONS: Our data may support the assumption of TNF alpha playing an important role in joint destruction in RA. Possible alternative conclusions are discussed.