A prosthetic disc for the replacement of a defective intervertebral disc comprising a lower component member and a upper component member, each component member having three distinct complementary bearing surfaces which allow anterior-posterior (bending forward/backward), medial-lateral (bending side-to-side), and twisting motions approximating the natural movement of a spinal joint. The lower component member has three adjacent bearing surfaces which are each longitudinally and medial-laterally convex. The upper component member has three substantially complementary longitudinally and medial-laterally concave bearing surfaces. When the prosthesis is disposed between adjacent vertebrae, it provides medial-lateral support while allowing anterior-posterior, medial-lateral and twisting motions approximating the natural movement of the spine.