Objective: We sought to clarify the nature of joint effusion (JE) on T2-weighted magnetic resonance images of the temporomandibular joint (TMJ) by analysis of the synovial fluid in the superior compartment of patients with internal derangement and osteoarthrosis.
Study design: One hundred symptomatic TMJs (100 patients) with 65 internal derangements and 35 osteoarthroses were scanned by means of magnetic resonance imaging, and, the synovial fluid was sampled on the same day. The amount of JE was evaluated on a scale of 0 to 3. Grades 0 and 1 indicated absence of JE or a negligible amount of JE, respectively, and grades 2 and 3 indicated the presence of JE. Correlation was evaluated among the amount of JE and the concentrations of the total protein and interleukin-1beta(IL-1beta), IL-6, IL-8, and tumor necrosis factor-alpha in the synovial fluid.
Results: Magnetic resonance imaging revealed the absence of JE in 40 joints (grade 0, 17 joints; grade 1, 23 joints) and the presence of JE in 60 joints (grade 2, 31 joints; grade 3, 29 joints). The joints with JE had, on average, significantly higher concentrations of total protein (1,675 microg vs 714 microg; P = .0001) and IL-6 (42.9 pg vs 10.6 pg; P = .009) than did the joints without JE. Furthermore, there were significant correlations between the JE grade and the concentrations of the total protein (P = .0001), IL-6 (P = .001), and IL-8 (P = .004). The detection ratio of cytokines among the presence-absence groups of JE showed a significant difference in tumor necrosis factor-alpha (68.3% vs 47.5%; P = .037) and IL-6 (86.7% vs 67.5%; P = .012). Conclusions. JE may contain the released products when there is pronounced synovitis. It is probably composed of high concentrations of total protein with inflammatory cytokines. Furthermore, IL-6 and IL-8 seem to have an important role in the pathogenesis of JE in TMJ disorders.