Histogram Parameters of the Infrapatellar Fat Pad Fat Fraction: Associations with Radiographic Severity of Knee Osteoarthritis.

RATIONALE AND

OBJECTIVES

The purpose of this study was to delineate the cross-sectional associations between the quantitative parameters of the infrapatellar fat pad (IPFP) histogram of the full-domain fat fraction (FF) and the radiographic severity of KOA.

METHODS

One hundred and twenty subjects were examined at our hospital. The severity of knee osteoarthritis was assessed according to the knee X-ray Kellgren-Lawrence grading (KLG). The mDIXON-Quant technique was used to obtain the IPFP full-domain FF and extract histogram parameters: mean, median, 10th percentile, 90th percentile, skewness, kurtosis, and entropy. Correlation and regression analyses assessed associations between FF parameter and KLG, and the diagnostic efficacy of each parameter was analyzed by applying receiver operating characteristic (ROC) curves.

RESULTS

Mean, median, 10th percentile, 90th percentile, and kurtosis of IPFP full-domain FF showed negative correlations with KLG (r = -0.563, -0.448, -0.614, -0.294, and -0.450, respectively), whereas skewness and entropy exhibited positive correlations (r = 0.385 and 0.637, respectively). After adjusting for age, sex, and BMI, the 10th percentile demonstrated the strongest association (β = -5.74; 95% CI: -7.02 to -4.46; P < 0.001). The areas under the ROC curves (AUCs) for diagnosing KOA were 0.799 (mean), 0.725 (median), 0.828 (10th percentile), 0.636 (90th percentile), 0.741 (kurtosis), 0.688 (skewness), and 0.830 (entropy). The 10th percentile and entropy showed sensitivities of 74.42% and 77.91%, and specificities of 85.29% and 88.24%, respectively.

CONCLUSION

The quantitative parameters of IPFP full-domain FF histogram correlate with the radiographic severity of KOA and may serve as objective imaging biomarkers for structural stratification.