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.