Quantitative signal intensity alteration in infrapatellar fat pad predicts incident radiographic osteoarthritis: the Osteoarthritis Initiative

Objective: To determine whether infrapatellar fat pad (IPFP) signal intensity measures are predictive of incident radiographic osteoarthritis (ROA) over 4 years in the Osteoarthritis Initiative study.

Methods: Case knees (n = 355), as defined by incident ROA, were matched 1:1 with control knees, according to sex, age, and radiographic status. T2-weighted magnetic resonance images were assessed at P0 (the visit when incident ROA was observed on a radiograph), P1 (1 year prior to P0), and baseline and used to assess IPFP signal intensity semiautomatically. Conditional logistic regression analyses were performed to assess the risk of incident ROA associated with IPFP signal intensity alteration, after adjustment for covariates.

Results: The mean age of the participants was 60.2 years, and most (66.7%) were female and overweight (mean body mass index 28.3 kg/m²). Baseline IPFP measures including the mean value and standard deviation of IPFP signal intensity, the mean value and standard deviation of IPFP high signal intensity, median and upper quartile values of IPFP high signal intensity, and the clustering effect of high signal intensity were associated with incident knee ROA over 4 years. All P1 IPFP measures were associated with incident ROA after 12 months. All P0 IPFP signal intensity measures were associated with ROA.

Conclusion: The quantitative segmentation of high signal intensity in the IPFP observed in our study confirms the findings of previous work based on semiquantitative assessment, suggesting the predictive validity of semiquantitative assessment of IPFP high signal intensity. The IPFP high signal intensity alteration could be an important imaging biomarker to predict the occurrence of ROA.