A prosthetic ankle joint comprising: a first component having a lower articular bearing surface, the first component being configured for connection to the distal end of the tibia such that the lower articular bearing surface is remote from the tibia a second component having an upper articular bearing surface, the second component being configured for connection to the tarsal bone such that the upper articular bearing surface is remote from the tarsal bone a third component interposed between the first and second component, the third component having an upper bearing surface configured to be slidable on the lower bearing surface of the first component and a lower bearing surface configured to be slidable on the upper surface of the second component wherein at least one of said components and/or said bearing surfaces being configured to allow the third component to be slidable in an anterior/posterior direction but to prevent the third component being slidable in a medial/lateral direction.
