13C NMR investigation of synovial fluids

13C NMR spectra of synovial fluids from 20 patients suffering from rheumatic diseases have been recorded. Structural changes in hyaluronic acid, the main carrier of the viscoelastic properties of synovial fluid, could be observed in the NMR spectra of the native biological fluid. By comparing these spectra with those of purified hyaluronic acid, a rough estimation of the degree of depolymerization of synovial hyaluronic acid was possible. The patients with rheumatoid arthritis appeared to have a lower degree of polymerization compared to patients with osteoarthrosis. Thus, 13C NMR spectroscopy provides useful information about biophysical properties of synovial fluid.