1. To determine whether the low-dose, biplanar x-ray imaging (EOS) has the same accuracy as computed axial tomography (CT)
2. To validate low-dose, biplanar x-ray imaging (EOS) as a tool to evaluate 3-dimensional alignment of Total Knee Replacement implants.
3. To evaluate differences in total knee replacement implant alignment in patients whose arthroplasty is performed using manual or custom instrumentation derived from preoperative CT

Achieving optimal prosthetic alignment of the femoral, tibial and patellar components during Total Knee Replacement (TKR) is of great importance as it contributes to better function, less pain and improved quality of life.TKR requires accuracy in the execution of bone cuts in the correct orientation to the coronal, sagittal and axial planes. Malposition potentially leads to increased mechanical stress on the bearing surfaces and inevitably to earlier loosening.

Computed Axial Tomography (CT) is the gold standard technique to evaluate implant alignment in the coronal, sagittal and axial planes. As such, CT has imaging has been used to create custom instrumentation with purported likely improvement in surgical outcomes. Customized instrumentation created from a preoperative CT has been shown to be safe and effective, with no reported difference in patient outcomes and similar total knee arthroplasty component alignment. However, taking into consideration CT's high levels of radiation, cost expenses and its inability to obtain images of the limb in weight-bearing position, CT scan cannot be used routinely as a postoperative tool to evaluate TKR implant positioning.

The imaging system manufactured by EOS Imaging (formerly Biospace Med, Paris) is a biplanar, low-dose radiation, full body, high resolution, radiological imaging system allowing simultaneous acquisition in the coronal and sagittal planes and in standing position.EOS' main benefits are the considerable reduction in radiation dose (up to 1000 times less than for CT and ten times less than the plain radiography) by using a gaseous detector. George Charpak, the inventor, was awarded the Nobel Prize in 1992 for this work. Moreover, the EOS system can provide 3D images by using the appropriate software algorithms, thus providing a low-radiation alternative to CT.

Inclusion Criteria:

• Radiographically confirmed diagnosis of osteoarthritis (OA)
• Failure of non-operative treatment for the diagnosis of symptomatic osteoarthritis
• Age greater than 18 years
• Desire to proceed with elective TKR
• Completion of informed consent and signature of written consent form

Exclusion Criteria:

• Ligamentous instability that may necessitate a constrained TKR implant
• Retained hardware in the distal femur or proximal tibia of the operative extremity
• Medical contraindication to undergo preoperative CT, or inability to tolerate preoperative CT

Intraoperative period - 6 wks. post-operative

Participation in this study does not expose participants to risks beyond or different from the risks associated with the total knee replacement surgery designated as standard of care.