I Have Arthritis In Both Knees. Sometime Very Painful Especially

I have arthritis in both knees. Sometime very painful especially at night. I am losing weight but I still weigh 250 pounds. Two doctors approved me for knee replacement surgery. The third said no because there is A major chance of complications at my age, 64, and medical conditions, type I I diabetic and high blood pressure. Should I wait before having the surgery.