Surgical Weight-Loss to Improve Functional Status Trajectories Following Total Knee Arthroplasty (SWIFT Trial)

Obese patients pursing a TKA procedure are typically encouraged to lose weight prior to the procedure as part of the patient's treatment plan. If the patient chooses to receive treatment for his or her obesity, the Orthopedic provider may refer the patient to a weight management provider. If a patient is eligible for TKA and meets the inclusion and exclusion criteria (containing BMI and corresponding comorbidity measures), he/she is eligible to participate in the study. In this study there will be two arms, a Test Arm in which patients undergo bariatric surgery prior to TKA and a Control Arm in which patients undergo TKA only. Patients will choose which arm they enter, based on whether or not they want to undergo surgical weight loss intervention prior to TKA. 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. Control Arm: Participants in the control arm undergo a total knee replacement without surgical weight loss intervention and will complete six (6) research visits over the course of 2.5-3 years, in addition to the standard of care visits required for 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 at the time of TKA. The study hypothesis is that weight loss induced by bariatric surgery prior to TKA will improve TKA outcomes in patients with extreme obesity. The study hypothesis will be met if one of the following outcomes is achieved: * In \>=20% of bariatric surgery patients, the need for TKA was negated or delayed for at least two years. * A statistically significant superiority is found among those patients undergoing bariatric surgery + TKA versus those undergoing TKA only in at least two of the following domains at two years post TKA: * Mobility (400 meter walk test) * Osteoarthritis outcome (WOMAC total score) * Knee orthopedic outcome (Knee Society score) * Quality of life (PROMIS-29 Quality of Life Questionnaire) * Osteoarthritic Pain (KOOS Pain) * Patient Satisfaction (If you had to live the rest of your life with the symptoms you have now, how would you feel?)