Association between the cartilage volume and bone mineral density in symptomatic knee osteoarthritis and the mediating role of bone mineral content

OBJECTIVE: To investigate the associations between cartilage volume and bone mineral density (BMD) in patients with symptomatic knee osteoarthritis, as well as mediating effect of bone mineral content (BMC). METHODS: A total of 172 subjects with symptomatic KOA were included in this study. Knee cartilage volume was measured from MRI. Total BMC and BMD at total body, spine and hip were measured by dual-energy X-ray absorptiometry. Linear regression analysis was used to detect the associations between cartilage volume and BMD. The indirect influence of total BMC on the associations between cartilage volume and BMD was examined using mediation analysis. RESULTS: This study of 172 symptomatic knee osteoarthritis patients (mean age 55.3 years) revealed significant positive associations between knee cartilage volumes and total body BMD, spine BMD and hip BMD after covariate adjustment (β = 0.026–0.111, all p < 0.05), with total cartilage and patellar (P) cartilage showing strongest correlations. BMC consistently mediated the cartilage-BMD relationships through three interconnected mechanisms: significant positive indirect effects (βInd = 0.062–0.184) operated across all cartilage compartments, while counteractive negative direct effects (c′=-0.019 to -0.070) emerged concurrently; The suppression effect indicated BMC’s role in systemically amplifying the cartilage-BMD linkage beyond localized inhibitory pathways. BMC accounted for > 170% of total effects, indicating its dominant role in translating cartilage integrity to systemic BMD enhancement while masking localized negative pathways. CONCLUSIONS: Cartilage volume positively correlates with systemic BMC and BMD. In symptomatic knee OA, BMC mediates this relationship and enhances integrated bone-cartilage metabolism by suppressing local inhibitory signals.