Relationship between the tensile properties of articular cartilage from the human knee and age.

The relationship between the tensile properties of articular cartilage and age has been investigated in vitro in the human knee joint. Specimens orientated parallel to the articular surface were excised from the superficial and deep zones of the femoral condyles of knee joints of persons in the age range from 8 to 91 years. The results showed that the tensile strength of the superficial zone increased with age to reach a maximum value in the third decade. Thereafter the strength decreased markedly with increasing age. The tensile strength of cartilage from the deep zone did not show an increase in the early years but decreased continuously with age. The tensile stiffness of the superficial layer at stresses of 5 MN/m2 and 10 MN/m2 increased to maximum values in the third decade and thereafter decreased with increasing age. The stiffness of the deep zone decreased continuously with age. It is suggested that these results reflect changes in the organisation of the collagen fibre mesh with age and possibly also changes in the collagen cross-links.