The joint prosthesis i.e. hip prosthesis (10), has components (13, 14, 18) cooperating with each other over joint surfaces for forming a sliding joint (16), and a joint casing (17) extending from one component to the other components, where the casing surrounds the sliding joint. A double wall is provided in a surface area of the casing and has an inner layer and an outer layer that are movable parallel and relative to each other. A friction-reduced coating is applied on the inner and outer layers, and a fluid layer or a gel layer is provided between the inner and outer layers.
