Integrated structural properties of cartilage, the combined structural behavior of a material (which accounts for both of its elastic properties and geometry) were measured in 25 autopsies and 35 open operations. The intraoperative measurements were made at the time of total knee arthroplasties, synovectomies, amputations, and traumatic lesions of the knee. The results obtained through evaluation of force deformation curves have been computer analyzed. There were no statistically significant differences between the stiffness of autopsy cartilage and in vivo cartilage as obtained through measurements at surgery. There was significant age dependence of stiffness of joint cartilage. Stiffness of intraoperative as of autopsy cartilage, depends on the thickness of the material tested.