Metal on Metal Versus Metal on Highly Crossed Linked Polyethylene Sytem

Inclusion Criteria: * Male and non-pregnant female subjects 65 years of age or older * Subjects undergoing cementless hip arthroplasty. If a press fit metal articulation acetabulum is not possible; the modular cup system will be utilized with screw fixation and a metal head of the greatest diameter deemed appropriate and safe for the patient will be utilized.(At the discretion of the surgeon). The cup in this situation may have a metal or poly articulation. The patient will be followed as an intent to treat (the patient will be evaluated and included in the group as randomized) * Subjects with, but not limited to, original diagnoses of osteoarthritis, avascular necrosis, rheumatoid arthritis, congenital dysplasia of the hip, ankylosing spondylitis, posttraumatic arthritis, and traumatic injury to the hip joint. * Subjects who are able and willing to understand the conditions of informed consent, to participate in the study according to the protocol for the length of the expected term of follow-up, and to follow their physician's directions. Exclusion Criteria: * Subjects undergoing hip arthroplasty using a cemented femoral component and/or a bipolar prosthesis. * Subjects with gross obesity, \>45% over ideal body weight for age and height. Refer to Appendix A, Obesity Table. * Subjects with active infections. * Subjects with malignancy in the area of the involved hip joint. * Subjects with a neuromuscular deficit that interferes with the subject's ability to limit weight b…