We have performed an RCT of cross-linked versus non cross-linked polyethylene with 125 patients followed for five years. The study showed a dramatic reduction of wear with the cross-linked polyethylene consistent with the in-vitro studies. Because it has been recognised that hard bearings are sensitive to edge loading we were concerned that highly cross-linked polyethylene might exhibit wear properties similar to hard bearings. We have therefore analysed the wear rate as it relates to both anteversion and tilt, to compare non cross-linked polyethylene with cross-linked polyethylene. We found that there was no relationship between tilt and ante-version on any wear indices. These data suggest that, despite having different mechanical properties to non cross-linked polyethylene, cross-linked polyethylene does not exhibit increased wear with conditions that increase edge loading.