All formulations of commercially available highly crosslinked ultra-high molecular weight polyethylene (UHMWPE) have demonstrated dramatic reduction in wear compared to conventional UHMWPE. A majority of these demonstrations have been under “smooth,” i.e., non-abrasive conditions. The question, therefore, remains: are contemporary highly crosslinked UHMWPE (XPE) materials suitable for both hips and knees under abrasive conditions in vivo? These studies examined both XPE (10Mrad, GUR1050) and non-irradiated UHMWPE (GUR1050) for hips and knees under smooth and abrasive conditions. Studies were conducted on a 12-station hip and 6-station knee simulator. The femoral components were left polished or tumbled with plastic cones and alumina powder to create uniform scratching with surface roughness similar to clinical retrievals. In smooth conditions, XPE wore significantly less than non-irradiated UHMWPE (CPE) for both hips and knees. In abrasive conditions, wear of XPE increased by at least 15 times in hip applications and at least 70 times in knee applications. Furthermore, XPE knees wore more than CPE knees in the abrasive condition. This study showed that both forms of UHMWPE were subject to accelerated wear under abrasive conditions; however, the sensitivity of XPE to abrasive wear was greater for knees than for hips. These findings need to be taken into consideration when developing materials for improved wear resistance in knees.