The symptoms of sore thighs while sleeping are most likely caused by the following diseases: 1. The most common cause that can trigger this symptom is muscle fatigue injury of the thighs. If during the day when the symptoms appear, excessive use of the thighs, excessive labor or exercise, can lead to the muscles of the thighs, fascia and other soft tissues, a transient injury, the injury leads to local exudate. The exudate can irritate the surrounding soft tissues and produce symptoms of thigh pain. The symptoms first appear at night on the same day, after lying down and resting the thigh activity decreases or even stops, the blood circulation in the thigh also gradually slows down, and the exudate that appears between the muscles of the thigh will be absorbed at a slower rate. But the speed of exudation must be, it will be in the leg rest not activity, the symptoms of soreness; 2, if the bed used is too soft, will make the lumbar spine deformation, a long time will stimulate the nerves around the lumbar spine, so that the thighs, and even the calves appear soreness and discomfort symptoms.