Objective: To explore the natural course of knee osteoarthritis (OA) in a middle-aged population with chronic knee pain.
Methods: A population-based sample of 143 subjects (mean age 45 (range 35–54), 44% women) with knee pain (>3 months) at inclusion was studied. Weight-bearing posteroanterior tibiofemoral (TF) radiographs were obtained at baseline and 12 years later, and classified according to Kellgren/Lawrence (K/L). Patellofemoral (PF) OA was determined at 5- and 12-years’ follow-up using a skyline view and a cut-off point of <5 mm joint space width. The ACR clinical criteria were used at baseline.
Results: Seventy-six (53%) had no TF OA (K/L 0) at baseline, but 49 had clinical OA. Overall, 65/76 (86%) developed incident TF OA over 12 years (K/L ⩾1): 44/49 (90%) of the subjects with clinical OA and 21/27 (78%) without clinical OA. Progression was found in 65/67 (97%) with TF OA at baseline. Of the 84 with no PF OA at the 5-year examination, 26 (31%) developed PF OA over 7 years.
Conclusion: A majority of the subjects with chronic knee pain developed knee OA over 12 years. It is concluded that knee pain is often the first sign of knee OA.
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Funding Grants were received from the Swedish Rheumatism Association, the Swedish National Insurance Agency, the Swedish Research Council, the Medical Faculty of Lund University and the Department of Research and Development at Spenshult.
Competing interests None.
Ethics approval Approval from Lund University Ethical Committee.
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