Normally the best way to train yourself to remember your dream signs is to take notice to them in waking life and do a reality check. You could reality check every time something weird happens to your legs. I doubt that happens often though, so it may not be the best approach in this situation.

To train myself to remember dream signs that rarely occur in waking life, I sort of train myself from the memories of dreams. Whenever you wake up from a dream with that dream sign, you should immediately repeat to yourself, "I should have reality checked". This should slowly train your mind to recognize it in your dreams.