I have a similar problem and stopped making the flight unless I can get the premium economy - it is more expensive than coach but a lot less than business. If you are not stuck with a certain airline shop around. The seat is wider and more leg room. I also ask for an aisle seat so it is easy to get up and walk around. Also I CAN walk and even if a wheel chair I bring a cane. People are more helpful if they can see you are handicapped, but I get a wheel chair now and spend at least 2 hours less at each end off my feet plus easier doing the lines, usually to the front of all lines. Passport control etc usually their own window. Because I have many metal parts and am old every advantage helps. No one gives you extra credit for suffering bravely so get every advantage you can.