Sprain pain in the middle of the night, the reasons include the following: First, sprain local soft tissue swelling, swelling gradually increased, when the swelling reaches the maximum degree, can compress the soft tissue nerve, causing pain symptoms, so the daytime sprain, the middle of the night, when the peak of the swelling occurred pain. Second, immediately after the daytime sprain swelling, pain treatment, pain symptoms tend to be light, normal people can tolerate, the second half of the night when the concentration of drugs to reduce the effectiveness of the drug decreased, pain symptoms can reappear. Third, during the daytime activities, the patient’s attention is more dispersed, and will be interfered by the environment and other people’s activities, and will not be concentrated on the injured part, and in the middle of the night when there is no other people’s activities and environmental interference, the patient’s attention is often concentrated on the injured part, and will be more concerned about the pain, and affected by the psychological factors, and feel that the symptoms of pain are aggravated.