OBJECTIVES To determine the prevalence of tibiofemoral radiographic knee osteoarthritis (OA) in people aged 35–54 years associated with chronic (> 3 months) knee pain using two different radiographic grading systems.

RESULTS A questionnaire was sent to 2000 randomly selected people aged 35–54 years. The response rate was 92.6%. Fifteen per cent of these people reported chronic knee pain. This group (n=279) was offered a clinical and radiographic examination of the knee joint and 204 persons agreed to participate. According to the Kellgren & Lawrence classification 28 subjects had OA of the knee grade 2 or more and 16 grade 3 or more. Radiographically detected OA of the knee according to Ahlbäck was found in 20 cases. The minimum prevalence of radiological tibiofemoral knee OA with knee pain was thus 1.5% for Kellgren & Lawrence grade 2 or more, 0.9% for grade 3 or more, and 1.1% according to the Ahlbäck classification. The agreement between the Kellgren & Lawrence grades 2–3 versus Ahlbäck grade I as well as grade 3–4 versus Ahlbäck grade I–II was good (κ 0.76 and 0.78 respectively).

CONCLUSION The prevalence of radiographic tibiofemoral OA combined with chronic knee pain in people aged 35–54 years was around 1% as estimated by either the Kellgren & Lawrence or the Ahlbäck classifications systems. Prospective follow up of this cohort should elucidate the significance of knee pain as a sign of developing OA.