Articular cartilage biology

Abstract

The composition and structure of its extracellular matrix gives articular cartilage the unique material properties that enable it to withstand compressive loads and to minimize friction between joint surfaces. This specialized matrix typically remains stable for decades despite the challenges of limited nutrition, hypoxia, and changing mechanical stresses. The cartilage matrix is elaborated and maintained by chondrocytes, which are metabolically well adapted to the articular environment. Chondrocytes are equipped with mechanosensory systems that allow adaptation to prevailing loading conditions. Normal physiologic loads are well tolerated and stimulate the biosynthesis of key matrix components. However, excessive loading, or the absence of loading, leads to loss of biosynthetic activity and increased matrix degradation. Declines in chondrocyte function or density associated with aging or acute mechanical injury are also thought to contribute to matrix degeneration. These factors may contribute to the pathogenesis of primary and post-traumatic osteoarthritis, respectively. Fortunately, recent findings suggest that aging and injury need not lead inevitably to arthritis: BMP and Wnt pathway modulators, antioxidants, caspase inhibitors, and membrane stabilizers all show promise as anti-degenerative agents that may mitigate the progression of arthritis.