Knee osteoarthritis (KOA) is the most common knee joint disease. Although KOA belongs to a disease of degeneration of knee joint cartilage, its pathology involves cartilage, subchondral bone, meniscus, synovial membrane, articular capsule and other joint tissue. The infrapatellar fat pad (IPFP), an intracapsular but extrasynovial structure, has some special characteristics of endocrine metabolism, then it has double roles in the development of KOA, but its protective effect is much more than harmful effect. Considering protective roles of IPFP in KOA and some serious complications after IPFP resection, the surgeon shall protect IPFP as far as possible if total knee arthroplasty surgical field is good. If it is necessary to improve the surgical field, its fibrotic tissue even all part can be removed.