Reply to the letter to editor by Macchi et al.

We thank Macchi et al. for their comments regarding our study describing regional differences between perisynovial and infrapatellar adipose tissue (AT) depots in patients with end stage osteoarthritis (OA) of the knee [1]. They summarize our findings concisely and contextualize this data with their own findings. The main goal of our paper was to quantify the differences between synovial and infrapatellar fat pad (IPFP) AT deposits from the same patient. The synovial AT had more pro-inflammatory/pro-fibrotic response than the IPFP in patients with obesity. We hypothesize that IPFP is a unique intra-articular tissue which plays a significant role in joint homeostasis and our findings support the importance of the IPFP in the development of OA [2]. We do believe, however, that the two AT examined respond to patient obesity in a different manner. This article is protected by copyright. All rights reserved.