Upper extremity fractures and subsequent total knee arthroplasty incidence in knee osteoarthritis: a cross-continental propensity score-matched cohort study

Knee osteoarthritis (KOA) represents a major clinical and economic burden globally, and total knee arthroplasty (TKA) remains the definitive treatment for end-stage disease. Upper extremity fractures in older adults often indicate skeletal fragility and reduced physiological reserve, but their influence on subsequent TKA incidence remains unclear. We investigated whether upper extremity fractures influence TKA incidence among patients with KOA. We conducted a retrospective propensity score-matched cohort study using the TriNetX US Collaborative Network (2005–2024) and performed external validation with the Asia-Pacific Research Network. Adults aged ≥ 50 years with KOA were identified; the exposure cohort included individuals who sustained upper extremity fractures after KOA diagnosis, while matched controls had no fractures. One-to-one propensity score matched more than 40 covariates, including demographics, comorbidities, and medications, with all standardized mean differences ≤ 0.02. The primary outcome was time to TKA at 1, 3, and 5 years, analyzed using Cox proportional hazards models with subgroup analyses by age and sex. Among 210,808 matched U.S. participants (105,404 pairs), upper extremity fractures were associated with significantly lower TKA utilization at 1 year (adjusted hazard ratio HR 0.25, 95% confidence interval CI 0.23–0.26), 3 years (HR 0.41, 95% CI 0.40–0.43), and 5 years (HR 0.50, 95% CI 0.48–0.52). External validation in 13,018 Asia-Pacific participants (6,509 matched pairs) yielded comparable results (1-year HR 0.25, 95% CI 0.19–0.33; 3-year HR 0.40, 95% CI 0.32–0.49; 5-year HR 0.48, 95% CI 0.40–0.59). Cumulative incidence curves demonstrated persistent divergence between groups in both cohorts (log-rank test, p < 0.001). Upper extremity fractures are associated with a 50% reduction in subsequent TKA utilization among adults with KOA, a finding replicated across geographically and ethnically diverse populations. These findings suggest that upper extremity fractures may serve as clinically actionable markers of systemic frailty that influence surgical utilization patterns and may inform individualized surgical timing and multidisciplinary osteoarthritis management strategies.