A prosthetic intervertebral disc joint assembly comprises two components 20, 30 for engaging the vertebra, each component having an intervertebral portion, a bone-engaging side and an inner side having an articulating surface, and a fixation portion 20b, 30b for securing the component to the anterior side of the vertebra. The articulating surfaces are partly spherical and match in curvature. The outer side of the first fixation portion is arranged so that it does not impinge on the second component in use. The fixation portions may be angled relative to the intervertebral plane. Each fixation portion has at least one bone screw aperture, which may be threaded, and preferably two diverging apertures. Each component may have a bearing insert made from cobalt chrome and a supporting body of titanium or titanium alloy. A kit of parts and method of installation are also provided.
