Some causes of leg pain while lying down are restless leg syndrome, advanced intermittent claudication and injuries, says MedicineNet and Mayo Clinic. Most of the time, doctors do not know what causes restless leg syndrome, where people experience leg cramping when they are trying to sleep, claims MedicineNet.
Medications ease the symptoms of restless leg syndrome, says MedicineNet. Making lifestyle choices such as quitting smoking, losing weight, reducing the intake of caffeine and drinking quinine water also treats the symptoms. Walking as exercise and taking iron supplements if the patient is iron-deficient also help.
The pain of early stage intermittent claudication usually eases when the person rests, says Mayo Clinic. However, if the condition is untreated the pain persists even when the person lies down.