Developing knee joint osteoarthritis: Clinical, radiographical and biochemical features

Abstract: The aim of this project was to study clinical, radiographical and biochemical features of developing, symptomatic knee osteoarthritis (OA) prospectively in individuals aged 35-54 from the general population. A questionnaire to a random sample of 2 000 individuals in the district of Laholm, Sweden, identified 279 individuals (15% of the population) with chronic (>3 months) knee pain. Of these, 204 accepted to participate in baseline examinations. The minimum prevalence of symptomatic tibiofemoral OA for the general population was 1.5 % according to the Kellgren and Lawrence radiographic system and 1.1 % according to the Ahlbäck system. The health status measured by SF-36 (Short Form 36) was impaired in individuals with symptomatic tibiofemoral OA compared both to those without radiographic changes (p at least <0.05) and to the general population in corresponding age groups (p at least <0.01). Clinical signs as measured by two independent rheumatologists showed a low interobserver agreement and a low association with radiographical signs of OA. The ratios between concentrations of aggrecan and COMP (cartilage oligomeric matrix protein) were higher in knee joint synovial lavage fluid of individuals with tibiofemoral OA than in those without OA (p<0.001). The serum levels of COMP were higher in those with bone scan abnormalities (p<0.01) and the serum concentrations of COMP increased (p<0.001) over a 3-year period in the individuals with radiographic OA after 3 years, but remained unchanged in the individuals with normal radiographs at follow up. Similar changes were found for serum BSP (bone sialoprotein) in relation to bone scan abnormalities (p<0.05) and the levels increased over the 3-year period in the group with radiographic OA at follow-up (p< 0.001). Radiographic knee OA and knee pain with impaired health status is frequently found in middle-aged individuals. Prospective monitoring of the individuals in this project including synovial fluid and serum measurements of tissue markers should add important information regarding pathogenetic features, prognostic markers and features of importance for development of therapy of knee OA.