Applying evidence-based cross-disciplinary concepts helps to explain the heterogeneity in pain, function, and biological measures in individuals with knee pain with/at risk of osteoarthritis

Introduction: Factors contributing to individual differences in knee osteoarthritis remain elusive. Dispositional traits and socioeconomic status are independent predictors of mental and physical health, although significant variability remains. Dispositional traits serve as the biological interface for life experiences. Objectives: We investigate group differences based on dispositional traits and poverty status, specific to (1) pain intensity and functional limitations and (2) biological measures, a clinical composite and brain age. Methods: Adults aged 45 to 85 years with knee pain associated with chronic musculoskeletal pain provided information on demographics, socioeconomic and psychosocial factors, pain, and physical function. Kellgren–Lawrence scores were determined from knee radiographs, the clinical composite from fasting blood draws, and brain age from MRI data. Results: One hundred seventy-three individuals participated in the study. Of those, 117 had protective dispositional traits (81 above poverty/36 in poverty), and 56 had vulnerable dispositional traits (24 above poverty/32 in poverty). With sex, study site, Kellgren–Lawrence score, and age/or image quality as covariates, significant group differences were observed across clinical pain (P, 0.001), functional limitations (P # 0.001), and brain age (P # 0.002) measures. Although not significant, the clinical composite measure aligned with the other outcome measures and demonstrated the hormesis inverted U pattern. Conclusions: Groups based on dispositional traits and socioeconomic status explain differing clinical outcomes. Consistent with the allostatic load and hormesis inverted U models, one group was in an adaptive health status, 2 groups were showing signs of developing load, and the fourth group showing signs of overload, at risk of worse health outcomes.