I had pain in my thighs like that with my first labor. I also described it like the world's worst charlie horse. dd was posterior. I was planning on using hypnobirthing but that was NOT happening with the back/thigh labor! I tried so hard to relax my legs during contractions but I couldn't stop my leg muscles from contracting any easier than I could stop my uterus from contracting. How did I do it without an epi? I did get one eventually, but not before laboring at home for nearly 2 days. I avoided it until then by being scared to death of hospitals in the south. After exhausting every pushing position imaginable, I did end up transferring and having a c-section
I did see a webster chiro throughout my 2nd pregnancy, and my labor experience was VASTLY different. I would compare the last 30 or so hours of my first labor to what the (reasonably brief) transition was like with my 2nd. Anterior baby, contractions all up front, and I was actually able to use some hypnobirthing skills. Like in the middle of a contraction I'd realize, oh, I'm tensing my legs, this is unnecessary and I'll be much more comfortable if I relax.. and then I'd just..relax them! I was pretty amazed that I was capable of it that time.