Age-related changes in the morphology and deformational behavior of knee joint cartilage

Objective. Alterations of cartilage morphology and mechanical properties oc cur in osteoarthritis, but it is unclear whether similar changes also take place physiologically during aging, in the absence of disease. In this in v ivo study, we tested the hypothesis that thinning of knee joint cartilage o ccurs with aging and that elderly subjects display a different amount of ca rtilage deformation than do young subjects. Methods. We evaluated 30 asymptomatic subjects ages 50-78 years. Morphologi c parameters for the knee cartilage (mean and maximum thickness, surface ar ea) were computed from magnetic resonance imaging data. Results were compar ed with those in 95 young asymptomatic subjects ages 20-30 years. Deformati on of the patellar cartilage was determined after the subjects performed 30 knee bends. Results. There was a significant reduction of patellar cartilage thickness in elderly women (-12%; P < 0.05), but not in elderly men (-6%). Femoral ca rtilage was significantly thinner in both sexes (-21% in women, -13% in men ; P < 0.01), whereas tibial cartilage thickness displayed only nonsignifica nt trends (-10% in women, -7% in men). Patellar cartilage deformation was - 2.6% in elderly women and -2.2% in elderly men. These values were significa ntly lower (P < 0.05) than those in young subjects. Conclusion. We confirmed the hypothesis that knee cartilage becomes thinner during aging, in the absence of cartilage disease, but that the amount of reduction differs between sexes and between compartments of the knee joint. We show that under in vivo loading conditions, elderly subjects display a lower level of cartilage deformation than do healthy young subjects.