Pathological human synovial fluids. Viscosity and boundary lubricating properties.

On human synovial fluids obtained during operations from the knee joints of 80 patients with different joing disease, relative viscosity was measured at 3 different shear rates and the boundary lubrication was tested by the coefficient of friction in an artificial rubber/glass system. The results were evaluated in relation to the operative findings. The viscosity showed statistically significant differences between the synovial fluids from the knee joints with rheumatoid arthritis, osteoarthritis, and torn menisci, being lowest in rheumatoid synovial fluid and highest in synovial fluids from knee joints with torn menisci. Correlations were found in the variations in the viscosity and the degree of synovitis. The boundary lubrication also showed different values inrelation to the different diseases. Synovial fluid from knee joints with torn menisci seemed to act as the best lubricant and significantly better than rheumatoid synovial fluid. Variations in the boundary lubrications reflect successive degrees of cartilage degeneration.