Pain radiating to the thighs usually occurs as the cervix
dilates to pass out the uterine contents. As you have neared completion of expulsion of products, dilatation of cervix is not needed now. Other possible causes of this pain could be local blood clotting, muscular spasm or referred pain
. The exact cause can be deduced only through a proper clinical examination and blood tests. Meanwhile, please do not stress
that limb, free any tight clothing and take simple analgesics. Hope this helps.