Role of radiography in predicting progression of osteoarthritis of the hip: prospective cohort study.

OBJECTIVES To investigate which variables identify people at high risk of progression of osteoarthritis of the hip. DESIGN Population based cohort study. SETTING Ommoord district in Rotterdam, Netherlands. PARTICIPANTS 1904 men and women aged 55 years and older from the Rotterdam study were selected on the basis of the presence of osteoarthritic signs on radiography at baseline, as defined by a Kellgren and Lawrence score > or = grade 1. MAIN OUTCOME MEASURES Radiological progression of osteoarthritis of the hip, defined as a decrease of joint space width (> or = 1.0 mm) at follow-up or the presence of a total hip replacement. METHODS Potential determinants of progression of hip osteoarthritis were collected at baseline. x Ray films of the hip at baseline and follow-up (mean follow-up time 6.6 years) were evaluated. Multivariate logistic regression models were used to assess the association between potential risk factors and progression of hip osteoarthritis. RESULTS In 13.1% (1904 subjects) of the study population (mean age 66.2 years), progression of hip osteoarthritis was evident on the radiograph. Starting with a simple model of only directly obtainable variables, the Kellgren and Lawrence score at baseline, when added to the model, was a strong predictor (odds ratio 5.8, 95% confidence interval 4.0 to 8.4), increasing to 24.3 (11.3 to 52.1) in subjects with hip pain at baseline. CONCLUSIONS The Kellgren and Lawrence score at baseline was by far the strongest predictor for progression of hip osteoarthritis, especially in patients with existing hip pain at baseline. In patients with hip pain, a radiograph has strong additional value in identifying those at high risk of progression of hip osteoarthritis.