Moreover, IHC analysis showed a very strong MMP-13 IR signal located in the area of calcification and subchondral bone, which could prove that cartilage degradative changes are not only associated with synovitis but are a secondary response to disturbances in bone homeostasis, which is in line with the mechanism proposed by Chu at al., 2019 [52]. This evidence concerns the gene MMP13 and synovitis.