Now I'm getting older, and really should be using such things, I've given up - except when I'm racing. Years ago it was all part of the warm-up ritual prior to every run. The stuff I used then was 'Dog Oil' which was originally developed by some chap who used it on his racing Greyhounds!
Nowadays I use 'Blue Ease Cream' (Holland & Barratts) for any aches, muscle pulls, knees, joint pains, etc... It's a really penetrating substance containing such peculiar things as Emu Oil, Aloe Vera, Arnica, Witch Hazel, Nettle Extact and goodness knows what besides. I sometimes used it when training in the really cold wet weather before Christmas, when I was still wearing shorts, but not since I acquired my snug running tights!
Prior to a race I'll spend 15 minutes massaging the stuff into my leg muscles to warm and soften them.
Cheers!