Only a few studies have identified prognostic factors indicating risk of future knee arthroplasty in patients with osteoarthritis (OA) of the knee. The Osteoarthritis Initiative (OAI) is a National Institutes of Health and privately funded cohort study of 4796 persons with or at high risk of knee OA. The OAI is ideally suited to a more extensive study of knee arthroplasty prognostic factors than has been undertaken. The purpose of our study was to identify patient factors which predict rapid progression to knee arthroplasty, defined as arthroplasty within three years of baseline data collection.

We used alternating logistic regression models to analyze complete three year follow-up data from the OAI on 4670 persons with, or at risk for knee OA, aged 45 to 79 years during the years 2004 to 2008.

A total of 128 knees (116 persons) underwent knee arthroplasty during the study period. After adjusting for known prognostic factors, several previously unidentified predictors of future knee arthroplasty were found including past history of knee surgery (RR=2.04, 95% CI=1.33, 3.13), knee flexion contracture in degrees (RR=1.06, 95% CI=1.02, 1.11) and pain, on a 0 to 10 scale, with active knee flexion (RR=1.58, 95% CI=1.04, 2.39).

This study identifies new and easily measured clinical variables that are associated with more rapid progression to arthroplasty. The data may help to inform both physicians and patients of medical history and clinical examination findings most highly associated with short-term arthroplasty.