Science, medicine, and the future: Treating joint damage in young people

Nearly a quarter of all severe ligament or capsular knee injuries that result in a haemarthrosis are associated with cartilage damage.1 2 Breakdown of the cartilage from trauma or disease results in severe pain and disability and may progress to early osteoarthritis. In young patients this cannot be treated by joint replacement because of the risks of early loosening and “wearing out” of the prosthesis after about 10 years. This article details some of the new techniques that are being developed to restore painless joint function and possibly prevent osteoarthritis. Our review is based on our personal experience of laboratory and clinical methods of repair of articular cartilage and a review of relevant current literature. We also included studies assessing outcome, the economics of surgery, and patients' quality of life and data from the proceedings of specialist societies. The articular cartilage that lines joints is tough and resilient. It is essentially composed of a type II collagen sponge supported by water held in place by proteoglycans produced by the chondrocytes embedded in the matrix. The collagen fibres are firmly embedded in the subchondral bone, giving stability to the cartilage. The fibres are arranged as overlapping leaves arising from the subchondral bone that rise to the surface and then bend over to form arches. The proteoglycans and cells are embedded within the collagen fibres (fig 1). Fig 1. Spatial relations of collagen, proteoglycans, and cells in cartilage Proteoglycans are long chain polysaccharides linked to hyaluronate that are negatively charged and hold water within the cartilage by osmotic pressure, thus maintaining the tension of the collagen mesh. However, if the proteoglycans are damaged by trauma or by other agents such as enzymes in inflammatory disease or infection then the proteoglycan structure disintegrates and the water holding capacity is lost, and progressive breakdown …