Increased body mass index is a predisposition for treatment by total hip replacement

We investigated the radiological and epidemiological data of 4,151 subjects followed up from 1976 to 2003 to determine individual risk factors for hip osteoarthritis (OA), hip pain and/or treatment by total hip replacement (THR). Pelvic radiographs recorded in 1992 were assessed for evidence of hip-joint degeneration and dysplasia. Sequential body mass index (BMI) measurements from 1976 to 1992, age, exposure to daily lifting and hip dysplasia were entered into logistic regression analyses. The prevalence of hip dysplasia ranged from 5.4% to 12.8% depending on the radiographical index used. Radiological hip OA prevalence was 1.0--2.5% in subjects <60 years of age and 4.4--5.3% in subjects >or=60 years of age. While radiological OA was significantly influenced by hip dysplasia in men and hip dysplasia and age in women, the risk of THR being performed was only influenced by BMI assessed in 1976. Hip-joint degeneration and treatment by THR do not necessarily share the same risk factors, and caution should be exercised in epidemiological studies in attributing one or the other as the end point of coxarthrosis.