Background Despite the high incidence of clinically established knee and hip osteoarthritis (OA), few data are available on risk factors for clinical worsening.
Objectives The aims are 1) to estimate the proportion of symptomatic knee and hip OA patients showing worsening at 2 years, after 3 months standardized conservative treatment, 2) to estimate the additional value of clinical criteria at 3 months in prediction worsening at 2 years compared to baseline values only.
Methods All 302 patients in this longitudinal study in secondary care (CONTROL-PRO: patients fulfilling clinical ACR criteria for knee or hip OA and not yet deemed eligible for arthroplasty), received conservative treatment (the first 3 months standardized) which comprised education, physical therapy, step up analgesics and advice on weight reduction if indicated. The Western Ontario and McMaster Universities of Osteoarthritis Index (WOMAC) was used to measure pain and physical functioning as well as a numeric rating scale measuring patient global assessment. Measurements were performed at baseline, 3 months and 2 years. Worsening at 2 years was operationalized as fulfilling recently validated clinical worsening criteria for knee and hip OA or total joint replacement (TJR) in the index joint. Logistic regression was used to estimate the additional value of the determinant fulfilling clinical worsening at 3 months as predictor for worsening at 2 years.
Results Baseline characteristics were 66% female, a mean age of 55.0 (SD 9.8) years, and median BMI of 27.9 kg/m2 (IQR 25.3–32.9). Median duration of symptoms was 3.8 years (IQR 1.6–10.4), the majority addressed the knee joint (84.8%) as index joint and 211 patients (69.9%) had Kellgren and Lawrence scores ≥2. A total of 79 (27.8%) and 181 patients (59.9%) clinically worsened at 3 months and 2 years respectively. 75 Out of 181 patients (41.4%) who worsened at 2 years, had undergone a TJR in the index joint on average 1.1 years (SD 0.5) after inclusion. Of these 181 patients who worsened over time, a lower proportion of patients underwent a TJR of the knee than a TJR of the hip in their index joint (34.5% versus 72.7% respectively, p<0.0001). Patients who clinically worsened at 3 months showed an increased odds ratio of 5.8 to clinically worsen at 2 years as well (95% CI 2.2–15.6, p<0.001). Similar results were obtained when only TJR at 2 years as outcome measure was used.
Conclusions A high proportion of knee and hip OA patients in secondary care who are not deemed yet eligible for surgery at inclusion, showed clinical worsening over 2 years, even after conservative treatment. At 2 years, we observed relatively less TJRs for knee OA than for hip OA. Our results show that clinical worsening at 3 months is a strong independent risk factor for worsening at 2 years. A short conservative treatment trial could thus be used in clinical practice to select patients in whom TJR should be considered.
Disclosure of Interest None declared
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