We see it a lot in MMA, and probably in Muay Thai too (never trained in that). Fighters kick the inner or outer thigh; from what I've seen, they usually kick quite low on the thigh, just a little above the knee area, because this is where it hurts the more (from experience at least).
When I try to do it in "light sparring with friends" (I have a martial arts background which doesn't employ low kick, they don't have any), they just raise their knee. In such a case, my kick is ineffective, and it's more painful for me than for them.
If someone without any martial arts background can lift their knee in time to avoid being hurt by my kick, how can I expect this technique to work with someone who has minimal training?
I guess that this kick could/should be "thrown" when the opponent doesn't expect it, so that they wouldn't have time to raise their knee and therefore receive a maximal impact. But again, watching UFC matches, they usually just throw the kicks "out of nowhere" and it seems to work.
Are there any tips to time the kick so the opponent doesn't block it with the knee? Is there something about the angle of the kick that would make it harder to block?
I'm looking for overall tips to connect more often and with more power on low kicks to the thigh.