Changes in cartilage and bone metabolism identified by serum markers in early osteoarthritis of the knee joint

Serum concentrations of two extracellular matrix molecules were determinedover a 3 yr period in individuals with chronic knee pain to investigatewhether sequential serum measurements of cartilage- and bone-derivedmolecular fragments reflect early stages of osteoarthritis (OA) of the kneejoints. Thirty-eight individuals with chronic knee pain (> 3 months atinclusion) with or without radiographic evidence of knee joint OA at the 3yr follow-up radiographic examination were studied. Serum concentrations ofcartilage oligomeric matrix protein (COMP) and bone sialoprotein (BSP)increased significantly (P < 0.001) in the 23 individuals withradiographic OA at follow-up, while remaining unchanged in the 15individuals with normal radiographs at follow-up. The baselineconcentrations of the two variables did not differ between the groups.These findings suggest that pathological processes in cartilage andsubchondral bone coincide in OA, and appear to be reflected by circulatinglevels of macromolecules released from cartilage and bone. Changes in serumlevels of COMP and BSP are potential tools in studies of knee joint OA insubjects with chronic knee pain.