When I fly with Easyjet, hand luggage only I take an extra medical bag. Easyjet only allow you one bag so you can't have any handbag etc only your small suitcase, so I take an extra 18L rucksack with my pump supplies in, at the desk I just tell them it's a medical bag, and it's no problem, obviously I could open it and show them what is in it and when I phoned they said I should have a hospital letter, which I do, but I have not been asked to open bag, or show letter so far. As I also have a twisted knee and am using a stick at the moment they also tend to put you though speedy boarding!