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

Patients with osteoarthritis (OA) affecting multiple joints experience greater pain than those with single-joint disease, yet most research examines isolated joints, leaving a gap in multi-joint disease. This study aimed to describe radiographic hip (rHOA) and knee OA (rKOA) within UK Biobank (UKB), exploring interrelationships across joints and associations with joint pain, body size, race and deprivation. This cross-sectional study applied machine learning to hip and knee dual-energy X-ray absorptiometry scans. Radiographic OA (rOA) was defined as custom grades ≥2. Joint pain was assessed through self-reported questionnaires. Logistic regression models examined bilateral and cross-joint associations, as well as associations with joint pain. Adjustments were made for age, sex, race, height, weight and deprivation. Among 59,475 individuals (mean age 65 years; range 45-85; SD 7.7; 52.8% female), rHOA prevalence was 4,098 (6.9%, right-side) and 4,841 (8.1%, left-side). The corresponding estimates for rKOA were 3,750 (6.3%) and 4,220 (7.1%). Overall, increasing grades of rOA and number of joints affected were more strongly associated with concurrent joint pain (four-joints: OR 4.3 [95%CI 2.6-7.2]). Regarding joint-interrelationships, bilateral associations were stronger at the knee (26.1 [24.1-28.2]) than the hip (5.6 [5.2-6.1]). Cross-joint associations (hip-knee) were weaker. BMI was more strongly associated with rKOA (1.57 [1.52-1.61]) than rHOA (1.05 [1.02-1.09]). Greater height was positively associated with rHOA but appeared protective for rKOA. Radiographic hip and knee OA exhibit distinct patterns of interrelationship, associations with symptoms and risk factors, suggesting heterogeneity in disease processes and the need for joint-specific treatment.