ABSTRACT
Cartilage contains a relatively small number of cells that elaborate an abundant extracellular matrix rich in proteoglycans (PGs) and collagens. The collagens form an insoluble network that gives cartilage its strength and tensile properties. This chapter summarizes the recent findings that have demonstrated that quantification of Keratan Sulfate in serum provides an excellent measure of the rate of catabolism of cartilage PGs. A number of recent studies have shown that quantitative or qualitative analyses of fragments of cartilage PGs in synovial fluid provide important new information about the catabolism of cartilage PGs in a single synovial joint. Whereas measurements of levels of cartilage PG epitopes in synovial fluid provide information about the catabolism of PGs in the cartilages in that joint, measurements of levels of cartilage PG-related epitopes in blood reflect the average of what is happening in all the cartilage in the body.
