Inclusion Criteria:  severe knee osteoarthritis and have a body-mass index (BMI; the weight in kilograms divided by the square of the height in meters) of 45 to 60  Exclusion Criteria:  previous total replacement of the same knee, a need for bilateral total knee replacement, and knee pain during the previous week that the patient rated at higher than 60 mm on a 100-mm visual-analogue scale. Also,prior bariatric or complex foregut surgery, significant cardiovascular, pulmonary, renal, liver, gastrointestinal, psychiatric disorders, pregnancy, malignancy within last 5 years, anemia, coagulopathy requiring anti-coagulation therapy.