TikkoRo,
I don't work for an airline so this is not an educated comment, and I don't know the extent of your disability, but can I suggest that you perhaps mention at check in that a seat with a little more leg room will help with your comfort. YOu obviously cannot be put in an exit asle so they may put you down for any available upgrades.
Other than that perhaps you should contact the airline before the date on which you fly and explain to them your problem as they may already have a procedure for cases such as yours.
Either way you are not doing an harm!
Good luck and enjoy our flight!
love
SMILE
