I Fell 2 Stories Back In 1981 , I. Injured

I fell 2 stories back in 1981 , I. Injured my lower right back witha crushed disc in my lower right back and around the year 2000 my knees started aching with osterosis and arthritis in both knees, I have a sciatic nerve in my left leg with pain shooting down my left side. I have trouble walking and am going for surgery on Jan 28. To get both knees done, total knee replacements i also. Weigh 400 lbs do you think I will have any difficulty with the surgery. I also have sleep apnea please let me know I am 61 years old, thank.you. YYYY@YYYY