An in vitro experimental technique was developed to measure the stress-distribution properties of this disc. Discs were tested for conditions of increasing load and decreasing congruity between loading surfaces. Peak stresses and pressure gradients increased linearly as load on the disc increased. For a given load, as congruity of the surfaces decreased, pressure gradients increased. The results demonstrate that the disc has only a limited capacity for stress distribution. Disc thickness was a critical factor determining the peak stresses measured under the disc.