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Synovial Fluid

General Discussion of Synovial Fluid

(see also: glycosaminoglycans and proteoglycans; friction and lubrication)

  • synovial fluid is an ultrafiltrate of blood plasma plus hyaluronic acid and glycoproteins;
  • synovial fluid resembles material in interstices of loose connective tissue in respect to both components;
  • rate and method of passage of substances into & out of synovial fluid depend upon the molecular size of the substance;
    • gases & crystalloids diffuse rapidly in both directions;
    • larger proteins appear to leave fluid by way of lymphatics;
    • particulate matter is taken up by macrophages, and its egress from the joint cavity is quite slow;
    • inflamed synovium contains large clefts which probably permit passage of molecules of almost any size;
  • one of main functions of the lining cells of synovium is to secrete certain components of the synovial fluid;
  • in addition to substances secreted by the lining cells, synovial fluid contains proteins that are electrophoretically and immunologically identical to plasma proteins;
    • these proteins come from blood that circulates in synovial membranes

synovial fluid is a non-newtonian fluid;

  • non-newtonian fluids are notable because their viscosity is not constant and inversely depends on shear rate;
  • relationship between viscosity and shear rate is determined by the alignment of the long-chain hyaluronate molecules as the fluid is sheared;

antibacterial properties:

changes in osteoarthritis

Synovial-Fluid Analysis (septic arthritis)

References