OP0292 TO EXPLORE LONGITUDINALLY IN KNEE OSTEOARTHRITIS IF INFRAPATELLAR FAT PAD MORPHOLOGY COULD BE A PROGNOSTIC MARKER WITH THE DISEASE SYMPTOMS, JOINT STRUCTURAL CHANGES, AND OUTCOMES: NOT A SIMPLE ANSWER TO A COMPLEX QUESTION
Authors: J. P. Pelletier, P. Paiement, F. Abram, M. Dorais, J. Martel-Pelletier
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Although knee osteoarthritis (OA) is the most prevalent chronic musculoskeletal debilitating disease, there is no recognized marker to stratify OA patients. The infrapatellar fat pad (IPFP), although not yet as widely studied as other knee tissues, has been recognized as a likely key player in OA. However, there is sparse and conflicting data about which of this tissue's morphology is the best forecasting marker of the disease's symptoms, joint structural changes, and patient outcomes. <h3>Objectives:</h3> We hypothesized that some knee IFPP morphological features at baseline could be used as a prognostic marker of the OA disease symptoms, progression, and knee replacement. We also explored whether IPFP morphology changes are associated with disease symptoms and joint structure changes over time. <h3>Methods:</h3> By using a longitudinal study (0-96 months), the target knees (n=1075) of participants from the Osteoarthritis Initiative (OAI) progressor cohort were analyzed for their structural changes using X-ray for joint space width (JSW) and quantitative and automated MRI for cartilage, bone marrow lesions (BML) and effusion volumes, as well as the IPFP morphology (total volume and maximal area, and hyperintensity signal volume and area). The symptoms were evaluated using WOMAC and KOOS scores. The knee replacement was as in the OAI database. The analyses were performed at baseline and 12, 24, 48, and 96 months post-inclusion. Changes over time were calculated as the value at the follow-up minus the one at study inclusion, divided by the value at study inclusion. Overtime evolution was analyzed using the mixed model for repeated measures (MMRM) and association by ANCOVA. <h3>Results:</h3> At baseline, a significant association was found between the IPFP total volume and maximal area, as well as hyperintensity signal volume and area with the cartilage (p≤0.001), effusion (p≤0.001; except IPFP area) and BML (p≤0.027; except hyperintensity signal) volumes. Over time (0-96 months), there was a decrease in disease symptoms (WOMAC, KOOS; p≤0.001), IPFP total volume and maximal area (p≤0.001), JSW (p&lt;0.001), cartilage volume (p&lt;0.001), and an increase in effusion (p&lt;0.001) and hyperintensity signal volume and area (p≤0.001). Importantly, significant associations were found between baseline hyperintensity signal volume with changes in JSW (96 months; p=0.008), cartilage (48 months; p=0.026) and effusion (96 months; p=0.038) volumes, as well as between the hyperintensity area with BML volume (12 months; p=0.044). Regarding the association for the changes of both IPFP morphology and knee structures, the most significant were the changes in the IPFP total volume with JSW (48 months; p&lt;0.001), cartilage (24, 48 months; p≤0.049) and BML (24 months; p&lt;0.02) volumes, and a trend toward significant difference at 12 and 48 months for BML and at 48 months for effusion volumes (p≤0.062). As for the disease symptoms or knee replacement, there was no association either at baseline or with the changes in the studied IPFP morphology. <h3>Conclusion:</h3> This extensive framework forecasting the progression of knee OA structural alterations revealed that the IPFP hyperintensity signal volume could be used as an early prognostic marker and that changes over time in the IPFP total volume were well associated with changes in the knee structural progression. This study offers a new approach for stratifying OA structural progressors. <h3>REFERENCES:</h3> <b>NIL.</b> <h3>Acknowledgements:</h3> The authors would like to thank the Osteoarthritis Initiative (OAI) participants and the Coordinating Center. The OAI is a public-private partnership funded by the National Institutes of Health. A special thanks to ArthroLab Inc. for providing the MRI data for this study. <h3>Disclosure of Interests:</h3> <b>None declared.</b>