I Need Left Knee Replacement Due To An Old Injury.

I need left knee replacement due to an old injury. I'm 76 yrs old in good health. I had one stent in RCA in March 30 2006 after heart attack. No problem since. My Doctor did an MRI prior to the knee surgery and found an aneurysm behind knee. He referred me to a Vascular Surgeon who did a sonargram and found one in right leg also. My questions are; should I have bypass surgery in one leg at a time or both? Can this be did during Knee replacement or should it be did before and if so, how long should I wait before knee replacement after the aneurysm surgery?