Volume of synovial fluid in normal and osteoarthritic human knee joints

The volume of synovial fluid in human knee joints was determined by the dilution method through the intra-articular injection of 35 ml 0.5% hydroxyethyl starch in saline. In 15 control knees the mean synovial volume was 6.7 +/- 2.3 ml (mean +/- S-D). In patients with latent gonarthrosis we found a mean intra-articular volume of 13.6 +/- 7.4 ml (n = 21) and in activated gonarthrosis 24.2 +/- 16.3 ml (n = 34). All 3 groups differ significantly. After entire aspiration of the effusion, we found yet 13.4 +/- 4.4 ml (n = 32) synovial fluid in the knee joint. Using the dilution method, we obtained a punctate from each knee joint. The punctates can be used for biochemical investigations. Since the dilution factors of the punctates are known, the concentrations of HWM parameters in the original synovial fluid can be calculated.