Permeability of synovial membrane to plasma proteins in human coxarthrosis: relation to molecular size and histologic...

The ratios of synovial fluid concentration to serum concentration (SF/S) for 4 nonimmunoglobulin proteins were higher in osteoarthritic synovia than in normal. The difference increased with increasing molecular weight and was highly significant for the largest molecules. An almost inverse linear relationship was observed between SF/S ratios of the proteins and their molecular weight. As only slight signs of inflammation were found in the osteoarthritic synovium, no correlation could be demonstrated between ratio and the degree of synovial inflammation as assessed by histologic methods. Two types of synovitis were encountered in patients with osteoarthritis: an early "proliferative" stage, characterized by synovial edema and large numbers of dilated venules and capillaries and a later "fibrous" stage characterized by scarring of the synovium. The highest ratios corresponded to the proliferative type. The abnormal protein pattern in osteoarthritic synovia is a result of increased capillary permeability in the synovial membrane owing to capillary dilation and stasis.