Measurements of nonhomogeneous, directional mechanical properties of articular cartilage in tension

The purpose of this investigation is to develop an accurate experimental procedure to measure the elastic properties of articular cartilage in uniaxial tension. Standardized, dumbbell shaped specimens, 250–325 μm thick, were taken from the surface, middle, and deep zones of the articular cartilage at 0°, 45°, and 90° from axis of the cleavage line pattern for the study of the zonal and directional properties of articular cartilage. A total of 75 specimens were tested to failure in this study. The use of a video dimensional analyzer system in this study makes accurate monitoring of the deformation of articular cartilage specimens possible. Nonlinear stress-strain relationships of the articular cartilage samples were mathematically approximated by exponential law similar to Fung (1967). Higher stiffness for the 0° specimens in the surface and middle zones was found. The experimental findings are in general agreement with the interpretations of low magnification scanning electron microscopy.