That is perfectly normal. When you reach your climax, the intensity of it, may cause your legs to cramp and have a numbness feeling in them. It's nothing too serious. But it is something, that you've found out, not very wanted. So I would say when you masturbate, ease up a little, and I know that's not easy to do, especially when you climax and ejaculate. Or shift your leg into a different position, so all of the strein doesn't go onto it.
I love you Danielle, and I always will!