Objectives: To determine clinical and ultrasonographic predictors of joint replacement surgery across Europe in primary osteoarthritis (OA) of the knee.
Methods: This was a 3-year prospective study of a painful OA knee cohort (from a EULAR-sponsored, multi-center study). All subjects had clinical evaluation, radiographs and ultrasonography (US) at study entry. The rate of knee replacement surgery over the 3-year follow-up period was determined using Kaplan-Meier survival data analyses. Predictive factors for joint replacement were identified by univariate Log-rank test then multivariate analysis using a Cox proportional-hazards regression model. Potential baseline predictors included demographic, clinical, radiographic and US features.
Results: Of the 600 original patients, 531 (88.5%), mean age 67±10 years, mean disease duration 6.1±6.9 years had follow-up data and were analysed. During follow-up (median 3yrs; range 0 to 4yrs), knee replacement was done or required for 94 patients (estimated event rate of 17.7%). In the multivariate analysis, predictors of joint replacement were: Kellgren & Lawrence radiographic grade (grade ≥ III vs < III, Hazards Ratio (HR) = 4.08 [95% CI = 2.34-7.12], p < 0.0001); ultrasonographic knee effusion (≥ 4 mm versus < 4 mm), HR = 2.63 [95% CI = 1.70-4.06], p < 0.0001); knee pain intensity on a 0-100 mm VAS (≥ 60 versus <60) HR= 1.81 [95% CI=1.15-2.83], p=0.01); and disease duration (≥ 5 years versus <5 yrs), HR= 1.63 [95% CI=1.08-2.47], p=0.02). Clinically detected effusion and US synovitis were not associated with joint replacement in the univariate analysis.
Conclusion: Longitudinal evaluation of this OA cohort demonstrated significant progression to joint replacement. In addition to severity of radiographic damage and pain, US detected effusion was a predictor of subsequent joint replacement. Osteoarthritis (OA) of the knee is a major problem for ageing Western populations (1). A major part of the economic burden is related to joint replacement surgery (2). It would be advantageous to have predictors of subsequent joint replacement in order to prioritise research in these patients, address reversible risk factors and provide cohorts for evaluating putative disease-modifying therapies (3). The limited prospective studies on joint replacement for OA suggest that radiographic severity, pain and global disease assessments, and willingness to consider surgery are the strongest predictors of subsequent joint replacement surgery (4, 5). Such research highlights the complexity of joint replacement as an outcome measure in clinical trials, as patient perceptions of need for surgery and potential side effects affect willingness to undergo a procedure, socio-economic features are important and these factors are reflected in regional and national variations in utilisation of joint replacement (3, 5).