Abstract
PURPOSE: This study aimed to explore the correlation between the proton density fat fraction (PDFF) of the infrapatellar fat pad and the severity of knee osteoarthritis (KOA), with a focus on identifying potential imaging biomarkers for KOA progression. METHODS: Seventy patients with KOA and forty-four healthy controls (HCs) were prospectively recruited for conventional MR and mDIXON-Quant sequence scanning. The mDIXON-Quant technique was selected for its precision in fat quantification and ability to provide three-dimensional water-fat separation, offering superior accuracy in assessing fat content compared to traditional methods.The severity of KOA was assessed via the whole-organ magnetic resonance imaging score (WORMS). Intraclass correlation coefficients (ICCs) were calculated to assess interobserver agreement for the PDFF measurements. Differences in the PDFF between KOA patients and HCs were compared. Additionally, the correlations between the PDFF of the infrapatellar fat pad in KOA patients and scores of the characteristic areas included in the knee WORMS were analyzed. RESULTS: The PDFF of the infrapatellar fat pad in KOA patients was significantly lower than in HCs. PDFF in KOA patients was negatively correlated with multiple aspects of total knee WORMS scores (e.g., articular cartilage integrity, etc.; r from - 0.94 to -0.25; P < 0.05), except for medial or lateral collateral ligament integrity (r = 0.27, P ≥ 0.05). Interobserver agreement was excellent (ICC = 0.793, P < 0.001). CONCLUSIONS: The PDFF of the infrapatellar fat pad is significantly associated with KOA severity, demonstrating a progressive decrease as the disease advances. These findings suggest that PDFF holds promise as a potential objective biomarker for evaluating KOA severity. However, further validation in larger and more diverse cohorts is required to confirm its clinical applicability. This study is a prospective investigation that adhered to the Declaration of Helsinki and was approved by the Ethics Committee of the First Hospital of Hebei Medical University (Approval No. [2024] Research Review No. 056).