Radiographic Hand Osteoarthritis in Adults Under 50: A Retrospective Cross-Sectional Study

The aim of this study was to determine the prevalence and distribution of radiographic hand osteoarthritis (HOA) in adults aged 18–50 years and to explore sex- and age-related differences in joint involvement. This retrospective cross-sectional study included 339 outpatients (107 men, 232 women; mean age 40.5 ± 8.2 years) examined at the National Institute of Rheumatic Diseases, Piešťany, Slovakia, in the first half of 2019. Bilateral hand radiographs were assessed for Kellgren–Lawrence (K–L) grade ≥ 2 in distal and proximal interphalangeal (DIP, PIP), metacarpophalangeal (MCP), thumb interphalangeal (IP), first carpometacarpal (CMC1), and trapezioscaphoid (TS) joints. Radiographs were independently read by two rheumatologists; intra-observer reproducibility in a random subset (n = 100) showed substantial agreement (κ = 0.82). Statistical analyses included chi-square and z-tests, with Spearman’s correlation for age-related trends. Radiographic HOA was present in 116 patients (34.2%). Prevalence increased with age, from 18.4% in those ≤ 35 years to 49.6% in those aged 46–50 (p < 0.001). DIP joints were most frequently affected, followed by CMC1 and PIP joints. MCP involvement was significantly more common in men (p = 0.008). These joint- and sex-specific patterns may reflect differences in mechanical load or hormonal influences. Age positively correlated with the number of affected joints (ρ = 0.25, p < 0.001), underscoring a progressive structural burden even within this younger age cohort. Potential confounders such as occupation, body mass index, and lifestyle were not accounted for and may influence the observed prevalence. Radiographic HOA is relatively common in adults under 50, with distinct age-, sex-, and joint-specific patterns. Our findings extend current knowledge by demonstrating that structural changes of HOA can occur much earlier than generally assumed and highlight the need for early recognition and preventive strategies in at-risk populations.