Advances in the role of the infrapatellar fat pad in the initiation and progression of knee osteoarthritis

Abstract

Osteoarthritis (OA) is a common chronic debilitating disease among middle-aged and old people, which can occur in the hip, knee, ankle, spine and other joints, but it is most commonly seen in the knee. The clinical manifestations of the knee osteoarthritis (KOA) include pain, swelling, stiffness, joint deformity, seriously affectting the quality of life. Mechanical and metabolic factors have been shown to play roles in the initiation and progression of this disease, resulting in a slow, progressive pathological process, and the normal balance of anabolic and catabolic activities of the chondrocytes has been disrupted. The mechanical factors are the joint imbalance caused by cartilage degeneration and ligament damage, and biochemical factors are mainly the changes of the joint microenvironment caused by the dysregulation of chondrocytes and synovitis. Infrapatellar fat pad (IPFP) is situated in the lower part of patella and femoral condyle, between tibia condyle and the patellar ligament, and it is an intracapsular but extrasynovial elastic fiber adipose tissue. Researches have shown that besides the synovial membrane, ligament, cartilage and bone, IPFP may play an important role in the onset and progression of KOA and knee pain. IPFP has long been regarded as a structural fatty tissue without metabolic reactions, thus often been neglected, what's more, to get a clear vision in knee surgery, IPFP is often partially or totally resected, but recently owning to its potential biological mechanics, endocrine function, which can produce a variety of inflammatory cytokines, chemokines, rich in nerve fiber structure and IPFP-adipose derived stem cells, more and more scholars pay attention to the IPFP. IPFP may play a protective role in the early stage of KOA by cushioning shock, stabilizing lubrication, but this article emphatically explain how IPFP play a desctructive role in the initiation and progression of KOA through leptin, adiponectin, and many other adipocytokines, or inflammatory mediators, so as to get further understanding of KOA, and discuss whether IPFP should be resected or not in knee surgery, providing a new method to the prevention and treatment of KOA.