Osteophyte size and location on hip DXA scans are associated with hip pain: findings from a cross sectional study in UK Biobank

Objective It remains unclear how the different features of radiographic hip osteoarthritis (rHOA) contribute to hip pain. We examined the relationship between rHOA, including its individual components, and hip pain using a novel dual-energy x-ray absorptiometry (DXA)-based method. Methods Hip DXAs were obtained from UK Biobank. An automated method was developed to obtain minimum joint space width (mJSW) from points placed around the femoral head and acetabulum. Osteophyte areas at the lateral acetabulum, superior and inferior femoral head were derived manually. Semi-quantitative measures of osteophytes and joint space narrowing (JSN) were combined to provide a measure of rHOA. Logistic regression was used to examine the relationships between these variables and hip pain, obtained via questionnaires. Results 6,807 hip DXAs were examined. rHOA was present in 353 [5.2%] individuals and was associated with hip pain [OR 2.07 (95% CI 1.54-2.80)] and hospital diagnosed OA [5.73 (2.89-11.36)]. Total osteophyte area and mJSW were associated with hip pain [1.29 (1.21-1.36), 0.84 (0.77-0.92) respectively] in unadjusted models. After mutually adjusting and adding demographic covariates, total osteophyte area continued to have strong evidence of association with hip pain [1.31 (1.23-1.39)] but mJSW did not [0.95 (0.87-1.04)]. Acetabular, superior and inferior femoral osteophyte areas were all independently associated with hip pain [1.19 (1.13-1.26), 1.22 (1.15-1.29), 1.21 (1.14-1.28) respectively]. Conclusion The relationship between DXA-derived rHOA and prevalent hip pain is explained by osteophyte area rather than mJSW. Osteophytes at different locations showed important, potentially independent, associations with hip pain, possibly reflecting the contribution of distinct biomechanical pathways.