A first prosthetic ankle component (10) comprising: a first bearing surface (12) configured to engage a second bearing surface (22) of a second prosthetic ankle component (20); and a protrusion (16) or slot (26) on the first bearing surface, the protrusion or slot being configured to engage a respective slot (26) or protrusion (16) in the second bearing surface of the second prosthetic ankle component, wherein the protrusion or slot is further configured such that the interaction with the respective slot or protrusion permits the first and second prosthetic ankle components to slide with respect to one another in an interface plane defined by the interface between the first and second bearing surfaces, and wherein the protrusion or slot is further configured to restrict the first and second prosthetic ankle components moving away from one another in a direction with a component perpendicular to the interface plane.