Human osteoarthrosis : lectin and histochemical studies of knee articular cartilage

Osteoarthrosis is a common condition affecting the articular cartilage of diarthrodial joints. This study was undertaken in two parts to review the lectin and histochemical staining characteristics of normal, aged and osteoarthrotic cartilage. Firstly, using a panel of histochemical stains the normal microanatomy of cartilage was reviewed with reference to the chondro-osseous junction. Secondly, using a panel of 19 lectins, carbohydrate expression of a number of parameters of the chondro-osseous sections was assessed. Three key findings were made in this study: 1. Ageing and early osteoarthrotic cartilage showed characteristic differences in their macroscopic and microscopic features. In particular ageing cartilage showed less loss of the normal viscoelastic response on indentation tests. At the microscopic level there was marked disruption of the normal chondrocyte architecture and chondro-osseous region and this was most pronounced in early osteoarthrosis. 2. The anatomy of the chondro-osseous region is more complex than previously documented. Clearly demonstrated were pegs of uncalcified cartilage faithfully followed by the tidemark dipping through calcified cartilage and abutting onto bone marrow spaces. 3. The main findings in relation to lectins were that: matrix staining was varied in normals in anatomical zones and regions and there were characteristic alterations in ageing and osteoarthrosis; chondrocyte cytoplasm and membrane staining was not always present suggesting that some cells may be metabolically active and others in a non-responsive phase; zone V matrix and uncalcified cartilage pegs exhibited a different staining pattern to the normal matrix indicating possible differences in function. Three main conclusions were made from these findings. Firstly, that the pathophysiological processes in ageing and early osteoarthrosis are fundamentally different, one being a natural physiological phenomena and the other exhibiting the hallmarks of a progressive disease process. Secondly, that the chondro-osseous junction region and tidemark remain poorly understood anatomical regions. The presence of interdigitating uncalcified cartilage pegs which connect with underlying bone marrow spaces suggesting this region may have a significant role in nutrition and possibly in the evolution of osteoarthrosis. Thirdly, the carbohydrates of cartilage glycoproteins play a significant role in the microenvironment of articular cartilage and subchondral bone and our current knowledge of the carbohydrate chemistry of cartilage is insufficient. That articular cartilage provides a unique role in maintaining mobility is demonstrated by the incapacity and morbidity that results from osteoarthrosis. A greater understanding of the chondro-osseous region and of cartilage carbohydrate chemistry may enhance our understanding of osteoarthrosis and assist in developing treatment strategies for this common articular disease.