Some biochemical and biophysical parameters for the study of the pathogenesis of osteoarthritis: a comparison between the processes of ageing and degeneration in human hip cartilage.

We have investigated the changes in some of the biochemical and biophysical properties of human femoral head cartilage on the one hand during ageing and on the other hand in osteoarthritis. Topographical variations were also investigated. The parameters studied were those relevant to cartilage function, viz., proteoglycan concentration (as expressed by the concentration of negatively charged groups), the rate of glycosaminoglycan synthesis, water content, osmotic pressure and fluid loss during compression. During ageing the fixed charge density was found to increase at all sites of the femoral head provided fibrillation was absent: osmotic pressure increased accordingly whilst loss of fluid under the effect of externally applied compression diminished. In cartilage from osteoarthritic joints the opposite changes were found. The rate of GAG synthesis varied considerably with site on the femoral head. It decreased somewhat with age on the superior surface, but increased on the inferior surface. When the same sites were compared, the rate of GAG synthesis in cartilage from osteoarthritic heads was either the same as or lower than in cartilage form normal heads in the same group.