RLS might be common, too
In people with fibromyalgia, restless leg syndrome, or RLS, is much more common than in the general population. Over 1/3 of people with fibro have reported symptoms of RLS, which include the sensation of needing to move the legs during sleep.
RLS can cause a nasty domino effect for people with fibromyalgia. Constantly waking up during the night leads to poorer sleep, which leads to tiredness, which could easily lead to more pain.