Mechanical properties of the normal human tibial cartilage-bone complex in relation to age

Objective. This study investigates the age-related variations in the mechanical properties of the normal human tibial cartilage-bone complex and the relationships between cartilage and bone. Design. A novel technique was applied to assess the mechanical properties of the cartilage and bone by means of testing the cartilage-bone complex. Background. Up to now, mechanical testing of cartilage and bone has been reported separately, and little is known about the mechanical behaviour of both tissues when examined as a unit. Methods. Cylindrical human proximal tibial cartilage-bone complex specimens from 31 normal donors aged 16-83 years were tested in compression. The deformation was measured simultaneously in bone and cartilage to obtain the mechanical properties of both tissues. Results. The stiffnesses and elastic energies of both cartilage and bone showed an initial increase, with maxima at 40 years, followed by a steady decline. The viscoelastic energy was maximal at younger ages (16-29 years), followed by a steady decline. The energy absorption capacity did not vary with age. Stiffnesses and elastic energies were correlated significantly between cartilage and bone. Conclusions. The present study demonstrates that similar age-related trends were seen in cartilage and bone, as if they behaved as a single mechanical unit.