The aim of this study is to determine the accuracy of long leg standing X-rays with respect to coronal alignment of the knee.

Long leg standing x-ray is a routine examination to measure the femoral valgus angle before a total knee arthroplasty. Newer studies have shown that coronal leg alignment influences the rotation of the distal femoral part. This rotation might influence the measurements obtained with a long leg standing x-ray.

The primary purpose of this study is to determine whether there is a significant difference between 2D measurements taken on the x-ray and 3D measurements obtained with a CT scan.

Inclusion Criteria:

Knee osteoarthritis scheduled for knee arthroplasty

Exclusion Criteria:

• previous leg deformities or surgery that changes alignment

All patients that require primary knee replacement will be enrolled in the study. Patients with prevoius surgery that might had already changed the leg aligment (hip/knee artroplasty, osteotomy) or patients with previous leg deformity are not eligible for the enrolment. Women in reproductive age are also not eligible.