I don't need one and in all honesty it wouldn't help me in the slightest, but as I have a back problem which means I cannot walk that fast (when I can walk at all) it would mean that there would be some visual sign of something wrong. Maybe then people wouldn't feel such need to make snidey comments about how slow I am while walking behind me! Especially when they are encouraging their child to announce loudly that I am far too slow.