A prosthesis for replacing a surface in an area of a ball of a ball-and-socket joint includes a spherical shell section having an outer surface that is configured to lie in an articular fossa and is for attachment to a surface. The shell section having a cavity for receiving a bone end. The prosthesis also includes a crown that partitions the cavity of the shell section into a first cavity and a second cavity wherein a shape of the shell section is at least a section of a hemisphere and a free edge of the crown lies in the same plane as a free edge of the shell section.