The purpose of this study is to evaluate the costs and benefits of the ConforMIS iTotal® total knee replacement system versus standard total knee arthroplasty.

This study is designed to illustrate the difference in cost between standard total knee replacements and the ConforMIS iTotal at a single institution.

STUDY DESIGN The study is a two-arm single-center, consecutively enrolled retrospective study. Patients enrolled will have previously received either an iTotal CR knee replacement or a standard total knee replacement. The study site will be located in the United States. A minimum of 100 with a maximum of 120 patients will be enrolled in each study arm for a maximum of 200 - 240 patients.

STUDY DURATION This study involves retrospective data collection of operative and peri-operative information to determine the cost impact of several surgical variables. The study will be complete when the retrospective data has been collected on up to 120 patients per arm.

Inclusion Criteria:

• Patient has received an iTotal or a standard total knee replacement
• Willingness to participate in the clinical study and to give informed consent, if necessary, as determined during IRB review
• >18 years of age

Exclusion Criteria:

• Participation in another clinical study that could confound results
• Patient is less than 3 months post-op

Patients who have had a Total Knee Replacement performed by the Investigator and are at least 3 months post surgery.