Test Arm: Participants will either undergo Laparoscopic Sleeve Gastrectomy or Laparoscopic Gastric Bypass surgery. Approximately 9-13 months post bariatric surgery, each test arm participant will be evaluated to determine if he/she is still a candidate or if the need for knee replacement no longer exists (or is delayed). If the participant is still a candidate, he/she will undergo TKA. Participants will complete nine (9) research visits over the course of 3.5 - 4 years, in addition to the standard of care visits required for bariatric surgery and TKA. Research visits will include study activities such as vital sign measurements, orthopedic outcome assessments, physical function assessments (i.e. stair climb, 400 meter walk, etc.), questionnaire completion, and synovial fluid collection if the patient has a TKA procedure performed.