A method is described, in outline, for measuring the compressive stiffness of articular cartilage on the human femoral head, in vitro. Indentations were measured normal to the articular surface, and from these measurements creep moduli were calculated at 2 sec after application of the load. Correlations between the stiffness and the following quantities were determined: (1) Total glycosaminoglycan content, (2) chondroitin sulphate content, (3) ‘keratin sulphate’ content, and (4) collagen content. These quantities were determined from chemical analyses of the indented areas of cartilage and expressed as a percentage of the dry weight.
The following observations were made: there was a statistically significant correlation between the stiffness, expressed as the creep modulus, and the total glycosaminoglycan content. Approximately equal correlation coefficients were recorded between the stiffness and chondroitin sulphate and ‘keratan sulphate’ content respectively; however, at a given concentration, the influence of ‘keratin sulphate’, on the stiffness, was greater than that of chondroitin sulphate. In contrast, the correlation between stiffness and collagen content was considerably less significant.