All patients will be DXA scanned pre-operatively for measurements of general bone mineral density and classification in a) normal bone, b) osteopenia) or c) osteoporosis. Patients with a T-score above -2.5 (normal bone and osteopenic bone) will be grouped and patients with a T-score at or below -2.5 and at or above - 4.0 will be grouped (osteoporosis). Patients will be stratified to the two treatment modalities (cemented acetabular cup fixation and cementless acetabular cup fixation) according to this dichotomy on T-score. Patients with a new diagnosis of osteoporosis will be referred to their own general practitioner concerning blood work and initiation of anti-resorptive treatment. On going medical treatment for osteoporosis will be recorded. After stratification according to T-score, patients are randomized during surgery with a cemented or cementless Avantage® dual-mobilty Cup (Biomet Inc.) and patients will be blinded with respect to implant fixation method. The Avantage® Cup can be inserted both cemented and uncemented where the cementless are HA coated and cemented cups are fully polished. The liner is gamma irradiated to induce a high level of crosslinking and Vitamin E is infused into the highly crosslinked polyethylene. A 28-mm chrome-cobalt femoral head will be used in all cases. The femoral stems will be similar in all patients (cemented Exeter stems, Stryker® Inc.) and Palacos® bone cement (Heraeus Medical inc.) will be used. During surgery 1mm tantalum beads are inserted in the bone surrounding the prosthetic components (both the femur and the cup) allowing for post-operative migration measurements with RSA.