A comprehensive descriptive analysis of hip and knee radiographic osteoarthritis in the UK Biobank in relation to joint pain, joint site interrelationships, obesity, race and deprivation: Findings from 59,475 individuals

<b>What is already known on this topic?:</b> Osteoarthritis (OA) commonly affects the hip and knee and is associated with pain and disability, with recognised risk factors such as age, obesity and deprivation.Increasing interest in multi-joint OA challenges the traditional concept of lower-limb OA as a monoarthritis, but most research examines joints in isolation.Genetic evidence suggests that hip and knee OA may differ in underlying mechanisms, yet population-scale comparisons are limited.<b>What this study adds?:</b> Among 59,574 individuals, this study identifies that radiographic OA captures structurally and clinically relevant disease with increasing severity and greater number of joints affected, positively associated with chronic joint pain.Radiographic hip and knee OA demonstrated strong bilateral but weaker cross-joint associations, indicating preferential within-joint symmetry.Risk factors differed by anatomical site with BMI and weight strongly associated with knee OA and weakly associated with hip OA. Height showed the opposite associations.<b>How this study might affect research, practice or policy?:</b> These findings support that hip and knee OA may partially represent different disease processes rather than a single condition.Clinical practice should consider cumulative joint involvement and joint-specific risk factors.Future research should consider the development of more targeted treatment to prevent multi-joint progression.