Cartilage destruction gradually occurs and is triggered by persistent synovitis, synovial hyperplasia, infiltration, and pannus formation during RA progression.48 Zhang et al. previously reported that knockout or pharmaceutical inhibition of FABP4 could significantly alleviate cartilage degradation, osteophyte formation and subchondral bone sclerosis in OA induced by a high-fat diet in mice, but it had no significant effect on lean mice that were fed a standard diet.49 However, Zhang et al. did not examine the source of FABP4 or the mechanism of FABP4 in chondrocytes in OA. Here, FABP4 is linked to rheumatoid arthritis.