A physical method is described for measuring the concentration of fixed negatively charged groups in articular cartilage. Comparison is made with values of fixed charged density derived from chemical analysis of hexuronic acid and total hexosamine contents. The mean deviation between values derived from the two methods was 10%.
This study was carried out on successive tangentially cut slices of human articular cartilage from the femoral condyle. The following observations were made. The fixed charge density increased with depth from the articular surface, as did the uronic acid and total hexosamine contents. In the 25–60 age group neither the hexuronic acid nor the total hexosamine contents showed any correlation with the age of the subject. However, there was considerable local variation and variation between individuals.