Synovial fluid and plasma levels of cartilage matrix glycoprotein in arthritis.

As cartilage matrix glycoprotein (CMGP) is a prominent matrix constituent, we analyzed the relationship of levels in plasma (CMGPP) and synovial fluid (CMGPS) to each other, to clinical diagnosis, and to degree of radiographic cartilage degeneration. CMGP was measured in matched synovial fluid and plasma specimens from 67 patients with various forms of arthritis using an ELISA technique. CMGPS consistently exceeded CMGPP, CMGPP levels correlated significantly with CMGPS levels, and CMGP retention in joint fluid, as calculated by the ratio CMGPS: CMGPP, was significantly higher in patients whose synovial fluids contain basic calcium phosphate crystals. No correlation of CMGPP or CMGPS with diagnosis or degree of cartilage degeneration was observed. CMGP measurements are not useful diagnostically in patients with chronic arthritis and do not predict degree of radiographic degeneration. The association of basic calcium phosphate crystals with intraarticular retention of CMGP warrants further study.