Nonspecific chronic synovitis of the knee joint was reported by Pollard in 1962 and its pathogenesis is considered to be a physiological reaction to intra-articular disease. In this study, we evaluated the pathological findings of the synovium of early osteoarthritis (OA)-affected knee joints with hydrarthrosis in comparison to typical OA.
Synovial tissues were harvested from early OA knee joints with hydrarthrosis graded 0-2 according to the Kellgren and Lawrence classification and examined by histopathology.
The synovial tissues showed proliferation of fibroblast-like synoviocytes (FLS) as if in rheumatoid arthritis (RA), and were immunohistochemically positive for matrix metalloproteinase 3, tumor necrosis factor α and interleukin 6.
The histology of RA is characterized by marked proliferation of FLS. In this study, the synovial tissues of early OA with hydrarthrosis showed moderate FLS proliferation. They also expressed the cytokines that are detected in the synovial tissues of RA. We suggest long-term follow-up is needed because early OA with hydrarthrosis might progress to overt RA.