This is a randomized clinical trial comparing two different uncemented femoral stems and two different uncemented sockets using Dual-energy x-ray absorptiometry, Radiostereometry and clinical evaluation.

Hypothesis:

1. A short uncemented stem gives less periprosthetic bone resorption in the proximal femur than a conventional uncemented stem.
2. An uncemented acetabular component with a backside of three-dimensional Titanium porous construct gives less periprosthetic bone resorption than a backside covered with a conventional porous coating with Titanium-beads and a hydroxy-apatite layer.

Consecutive patients 40-70 years old who are being planned for Total Hip Arthroplasty (THA) will be eligible for inclusion in the study.

Periprosthetic bone remodeling, migration of the components and clinical scores will be recorded prospectively.

Inclusion Criteria:

1. Age 40-70 years old
2. Primary osteoarthritis of the hip
3. Type A or B femur according to Dorr10
4. Femoral anatomy allowing implantation of both femoral stems
5. Willingness and ability to follow study-protocol -

Exclusion Criteria:

1. Inflammatory arthritis
2. Abnormal femoral anatomy after hip dysplasia, not suitable for implantation of components
3. Treatment with bisphosphonates, cortisol or cytostatic drugs 6 months prior to surgery
4. Ongoing oestrogen treatment
5. Type C femur according to Dorr
6. Not suited for the study for other reason (surgeons preference)