ADVERTISEMENT Just to break this down a bit, basically the pelvic region (where the ol' uterus has residency) is made up of a network of nerves - so when pain develops, it may radiate to some of the neighbours - such as your upper legs. Some people might also develop these kinds of leg pains or muscle cramps during their period because of a reduction in the level of minerals such as iron, magnesium and potassium (cause: loss of blood). Weird, right? Of course, if you experience severe leg pain during your period, it's best to consult a gynecologist to rule out the possibility of underlying medical problems.