OPPORTUNISTIC POPLITEAL ARTERY ASSESSMENT ON KNEE MRI AND MEDIAL TIBIAL STRUCTURAL DAMAGE IN OSTEOARTHRITIS: FNIH DATA.

INTRODUCTION: Vascular pathology has been proposed as a contributor to knee OA structural damage, but evidence remains inconsistent. Popliteal artery wall biomarkers extracted opportunistically from knee MRI may help characterize vascular-related structural phenotypes. OBJECTIVE: To evaluate whether baseline MRI-derived popliteal artery wall biomarkers are associated with baseline severity and 24-month worsening of medial tibial cartilage loss and bone marrow lesions (BMLs) in the FNIH Osteoarthritis Biomarkers Consortium. METHODS: This analysis included 600 FNIH participants, with one knee per participant. Baseline sagittal 3D DESS knee MRI was processed using FRAPPE, a fully automated popliteal artery wall segmentation tool, to extract eccentricity ratio (maximum-to-minimum wall thickness ratio), normalized wall index (wall area divided by total vessel area), wall area, and lumen area. Baseline and 24-month MRI were assessed by two musculoskeletal radiologists using MOAKS. Linear regression models evaluated associations with medial tibial cartilage damage and BML scores and 24-month worsening, adjusting for age, sex, BMI, and FNIH subgroup. RESULTS: Mean age was 61.6 ± 8.9 years, mean BMI was 30.7 ± 4.8 kg/m², and 353/600 participants (58.8%) were female. Higher eccentricity ratio was associated with greater baseline medial tibial cartilage loss, including more involved subregions (β=0.44, 95% CI 0.09-0.79; p<0.05), higher summed full-thickness damage MOAKS scores (β=0.49, 95% CI 0.18-0.80; p<0.01), and higher summed surface-area damage MOAKS scores (β=0.88, 95% CI 0.16-1.60; p<0.05). Higher eccentricity ratio was also associated with greater medial tibial BML burden, including more involved subregions (β=0.40, 95% CI 0.10-0.70; p<0.01) and higher summed BML size MOAKS scores (β=0.67, 95% CI 0.16-1.17; p<0.01). Popliteal artery wall biomarkers were not associated with 24-month worsening of cartilage loss or BMLs. CONCLUSION: Popliteal artery wall eccentricity on knee MRI was associated with greater baseline medial tibial cartilage loss and BML severity, but not with 24-month worsening. Opportunistic vascular assessment on knee MRI may help characterize vascular-related baseline structural disease burden in knee OA.