Proteoglycan fragments in joint fluid. Influence of arthrosis and inflammation

We determined the concentration of proteoglycan fragments in knee joint fluid collected from knee-ligament injured patients more than 6 months after the trauma and from patients with acute pyrophosphate arthritis and arthrosis or with arthrosis only. Injured patients with normal or only mildly altered cartilage at arthroscopy and with normal radiographs, had twice the average concentration of healthy volunteers. Other injured patients with advanced, radiographic signs of arthrosis, had synovial fluid proteoglycan fragment concentrations within the range of healthy volunteers. Patients with pyrophosphate arthritis had the highest concentrations, substantially increased compared with both arthrosis patients, with or without knee injury and healthy volunteers. Likewise, there was an inverse relation between the degree of arthrosis and the concentration of proteoglycan fragments in the joint fluid in patients with pyrophosphate arthritis and arthrosis or with arthrosis only. We conclude that synovial fluid levels of proteoglycan fragments are influenced by the mass of cartilage matrix remaining in the joint, the inflammatory activity in the joint, and the metabolic activity of the cartilage cells.