I have worked extensively for many years on the treatment of nocturnal cramps or Restless Leg Syndrome(RLS) and have come to the conclusion that the majority (not all) are caused by neuropraxia of the common peroneal nerve as it winds around the head of fibula. This, in turn, may be caused by an L5 lesion or a repetitive lateral ankle strain causing weakness in the ankle everters.
It can be remedied by mobilising the head of fibula, either by finger pressure (as in Maitland) or by Impact Therapy (IT) with the use of small sand and seed bags. Acupuncture/acupressure along the gall bladder meridian will also help.