Changes in structure and symptoms in knee osteoarthritis and prediction of future knee replacement over 8 years

The objective of this study was to assess the association between changes in joint space width (JSW, i.e., structure) or Western Ontario and McMaster Universities (WOMAC) score (i.e., symptoms) over 3 years in patients with knee osteoarthritis and the occurrence of knee replacement over 8 years. We followed 133 subjects with primary knee osteoarthritis prospectively for a mean of 8 years. JSW (standard radiography) and symptoms (total WOMAC score) were assessed every year for 3 years. The rate of knee replacement was recorded for the following 5 years. Logistic regressions were performed according to the intention-to-treat principle. After 8 years' follow-up, ten patients (7.5 %) had undergone a knee replacement. The changes in JSW or WOMAC score over 3 years were significantly associated with the occurrence of knee replacement during the following 5 years (p = 0.02 and p = 0.03, respectively). Each 0.1-mm narrowing of JSW over 3 years was associated with a 14 % (95 % CI 3-25 %) increased risk for knee replacement. For every 10 % increase in WOMAC score, the risk for joint replacement was increased by 16 % (95 % CI 1-33 %). When JSW and WOMAC score were included in the same statistical model, they were still significantly associated with risk for knee replacement (p = 0.02 and p = 0.03, respectively), but JSW change was the only variable that remained significant after adjusting for all potential confounders. Our results suggest that changes in symptoms and, more particularly, in structure over 3 years in patients with osteoarthritis reflect a clinically relevant progression of the disease.