Hyaluronan reduces fluid escape rate from rabbit knee joints disparately from its effect on fluidity

The effect of hyaluronan, the major viscous component of synovial fluid, on trans-synovial flow was measured in rabbit knees. Hyaluronan reduced fluid escape rate by up to 45%. This was much less than the reduction in intra-articular fluidity (1/viscosity). Electron micrographs supported the view that hyaluronan might be partially reflected by synovium, creating a molecular filtercake at the surface.