Brief Summary:

All artificial joint implants need to be solidly held (fixed) within the bone. Cementless fixation has become a popular method to achieve fixation for total knee replacements where the bone grows directly onto the implanted device instead of using bone cement. The primary purpose of this study is to assess long-term implant survivorship and clinical outcomes of a previous study cohort that received a cementless knee replacement. As this study cohort approaches 5 years post-operation, the investigators will re-examine the stability of participant implants using specialized x-rays, called "radiostereometric analysis". The study will use weight-bearing computed tomography (CT) to measure bone density and texture features and correlate that with implant stability. The investigators will collect stool samples to assess participant gut microbiomes for biomarkers of poor bone quality that could correlate to implant stability. All 33 participants from the original study cohort will be invited to participate in this study.