Infrapatellar fat pad area on knee MRI: does it correlate with the extent of knee osteoarthritis?

Abstract

Abstract Background Osteoarthritis (OA) of the knee joint is a common cause of chronic disability in older adults. During the past 10 years, the infrapatellar fat pad (IPFP) has emerged as a new player in the pathogenesis of knee OA. Its exact role in the pathogenesis of knee OA remains uncertain. While many studies focused on the detrimental effect of the chemical mediators released by IPFP and their role in the accentuation of the development of OA, only few studies elucidated the beneficial effect of IPFP maximal area as a local shock absorber protecting the adjacent articular structures from progressive damage. The aim of this study was to evaluate the relation between the IPFP maximal area and the prevalence of OA manifestations. We also studied the relation between the subcutaneous (SC) fat thicknesses on the medial aspect of the knee as a surrogate marker of body obesity and the IPFP area. Results A total of 216 knee scans for 188 adult patients (64 males and 124 females) who met the inclusion criteria were examined. They were between 45 and 66 years (mean 52.5 years). The mean IPFP area for all patients was 6.9 cm2 (± 1.6 SD) (ranged from 4.5 to 11 cm2). After adjustment for potential confounders, there was a significant negative association between IPFP area and radiographic manifestations of OA (osteophites, joint space narrowing, and grade of OA) (P value < 0.001 for each), as well as MRI manifestations of OA (cartilage defects and subchondral bone marrow lesions) (P value < 0.001 and < 0.003, respectively). There was a negative but non-significant association between IPFP area and SC fat thickness. Conclusion In our study, we found supportive evidence that IPFP maximal area is associated with fewer osteoarthritic knee changes and less cartilage damage, suggesting that it plays a protective role against the development and progression of OA. Further large-scale clinical studies are awaited to confirm the obtained results. Based on our findings, it would be recommended to avoid IPFP resection during surgery in order to maintain its protective effect.