An acetabular joint prosthesis may be designed to replace an acetabular articular surface. The prosthesis can include an acetabular cup, an augment, and an augment-securing mechanism configured to secure the augment to the cup. The mechanism can be reconfigured between an unlocked configuration in which a slider is slidable along a guide feature and a locked configuration in which the slider or guide feature is in an expanded form such that the slider is fixed in place relative to the guide feature. An unlocked configuration may include the augment-securing mechanism allowing rotation between the augment and the cup, with the augment being securable to the augment in multiple rotational positions. Also, the prosthesis may be configured to facilitate actuation between the unlocked and locked configurations, including moving an instrument to the prosthesis in an access direction that is substantially perpendicular to a rim of the cup.