Using the apparatus and technique described in an earlier paper, (
Kempson et al. 1971), indentation tests were performed on areas of cartilage of 0.125 in dia., in situ on, and distributed evenly over, the cartilage surface of the human femoral head. Curves of indentation vs. time were plotted for a physiological stress of approximately 400 lbf/in². (28.2 kgf/cm², 2.36 MN/m²). The stiffness of each area of cartilage was calculated from the appropriate indentation value, in the form of a creep modulus at 2 sec, using the equations described in the previous paper (see Appendix). Layered maps and histograms showing the variation of both cartilage stiffness and indentation are presented.