Objective: The purpose of this study was to evaluate the MRI characteristics of the suprapatellar fat-pad, determine the prevalence and pattern of suprapatellar fat-pad edema, and correlate the findings with the presence of anterior knee pain, patellofemoral malalignment, and patellofemoral joint osteoarthritis.
Materials and methods: We retrospectively reviewed 879 consecutive knee MRI examinations of 843 patients for the presence of a suprapatellar fat-pad mass effect on the suprapatellar joint recess. The relative signal intensity and the maximum anteroposterior, craniocaudal, and oblique diameters of the suprapatellar fat-pad on sagittal fat-suppressed intermediate-weighted turbo spin-echo images were measured. Findings of anterior knee pain, patellofemoral malalignment, and patellofemoral joint osteoarthritis were also recorded. The Fisher exact, Mann-Whitney, and independent samples Student t tests and Spearman rank correlation coefficient were used for statistical analysis.
Results: The prevalence of suprapatellar fat-pad mass effect on the suprapatellar joint recess in our study population was 13.8%. The relative signal intensity (p < 0.0001) and maximum anteroposterior (p < 0.0001), craniocaudal (p = 0.0017), and oblique (p < 0.0001) diameters of the pad were significantly greater in patients with a mass effect. Significant correlation was found between the relative signal intensity and the maximum anteroposterior (ρ = 0.0986, p = 0.0053), craniocaudal (ρ = 0.0968, p = 0.0062), and oblique (ρ = 0.123, p = 0.0005) diameters. Mass effect was not significantly associated with anterior knee pain, patellofemoral malalignment, or patellofemoral joint osteoarthritis. Six patients with suprapatellar fat-pad edema had anterior knee pain.
Conclusion: Suprapatellar fat-pad edema with a mass effect on the suprapatellar joint recess is a common finding at MRI examinations of the knee that is rarely associated with anterior knee pain.