A ceramic acetabular cup devoid of a separate liner comprises a part-spherical inner articulating surface and an outer surface. An inner radius at or adjacent to a rim of the cup extends to or adjacent to a surface edge of the inner articulating surface. An inner radius of the inner articulating surface defines an active arc, and an uppermost portion of the rim defines an offset datum plane. An offset is provided between an equatorial centre of the inner articulating surface and the offset datum plane. The active arc extends in a range from around 150 degrees to less than 180 degrees, and a distance between the inner articulating surface and outer surface on a straight line from the said equatorial centre and passing through the surface edge is equal to or less than 4 mm.