RA Synovial Fluid Viscosity

[seminoma]

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Why does synovial fluid viscosity decrease in RA? Pathoma says RA synovial fluid has increased PMNs and high protein.. Shouldn't cells and protein make it more viscous?

 

[mcloaf]

Why does synovial fluid viscosity decrease in RA? Pathoma says RA synovial fluid has increased PMNs and high protein.. Shouldn't cells and protein make it more viscous?

I have no clue since we haven't covered RA yet, but my assumption would be that the PMNs are breaking down the long polymers that make synovial fluid viscous like hyaluronan. So even if the fluid is high in protein, it's becoming lower in the glycosaminoglycans that increase viscosity in non-pathologic situations.

 

[Phloston]

Strange. But wouldn't show up in a million years so I think you'll be fine. Maybe extravasation of additional fluid into the joint decreases viscosity because, irrespective of the protein and/or WBC concentration, any additional fluid is less viscous than what's normally in the joint.