A lumbar disc prosthesis (2) is provided including a pair of disc members. The first member (4) of the disc pair has a vertebral disc contact surface (8) and a recessed portion (18) on an opposing surface (10) thereof. The second member (6) of the disc pair has a vertebral disc contact surface (14) and a protuding portion (16) on an opposing surface (12) thereof. The protuding portion of the second member engages with the recessed portion of the first member in use. Each of the first and second disc members may be provided with at least three sections; a middle section (44;40) and two end sections (46,48;36,38). The recessed and protuding portions are provided in the middle section of the respective disc members and each of the two end sections have a narrowing taper (24,26) towards the ends of the disc members. In addition the prosthesis includes a further pair of disc members (4',6') and may form a system with a facet joint replacement prosthesis (192,202).