Clinical and ultrasonographic predictors of joint replacement for knee osteoarthritis: results from a large, 3-year, prospective EULAR study

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, multicentre 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 3 years;
range 0-4 years), knee replacement was done or required for 94 patients
(estimated event rate of 17.7%). In the multivariate analysis, predictors of
joint replacement were as follows: Kellgren and Lawrence radiographic grade
(grade > or =III vs <III, hazards ratio (HR) = 4.08 (95% CI 2.34 to 7.12),
p<0.0001); ultrasonographic knee effusion (> or =4 mm vs <4 mm) (HR = 2.63 (95%
CI 1.70 to 4.06), p<0.0001); knee pain intensity on a 0-100 mm visual analogue
scale (> or =60 vs <60) (HR = 1.81 (95% CI 1.15 to 2.83), p=0.01) and disease
duration (> or =5 years vs <5 years) (HR=1.63 (95% CI 1.08 to 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.