An alignment guide for guiding the positioning of an acetabular cup implant includes a body having a first end and a second end. A flange extends from the first end and is adapted to rest on a labrum of an acetabulum. At least a first formation is provided at the second end which is adapted to engage with a transverse acetabular ligament of the acetabulum. A formation for accepting a trackable instrument is provided to allow a tracking system to determine the orientation of the guide.
