Many seniors or parents have experienced a child crying about leg pain. Since it is mostly at night, they often do not go to the hospital to see a doctor. By the time the child goes to the doctor the next day, the pain has disappeared. Why does this happen? The reason is simple: It is due to the excessive activity of small children running and jumping during the day, resulting in minor damage to the muscles, tendons, fascia and other soft tissues around the knee. During the day when the environment is distracting and the child is relatively distracted, the child does not feel this minor injury. By evening rest, when the environmental distractions are reduced, the pain of the minor injury becomes apparent. This is why most leg pain in children occurs at night and during sleep. Since small children are in the growth phase, nighttime sleep is a time for the body to grow. Through the process of growth, the damage is quickly repaired. This is the reason why after a night’s sleep, pediatric leg pain disappears. This is also the reason why both the elderly and the pediatricians have leg pain at night, the pediatricians sleep through the night and the elderly still have pain the next day. This is because the elderly no longer grow and the repair process slows down. Why do not all children develop leg pain? This is due to the innate physical genetics of the pediatrician. Different families with different genetic heritage develop different constitutions. Children with a strong constitution are less prone to injury. Children who develop leg pain are basically children who have a poorer constitution and take longer to recover from an injury. Is it possible for a child who is born with a poor constitution to become strong by supplementation? It is not possible. The replication of body cells depends on the genes formed in the embryo (in the mother’s womb), and these genes do not change after the formation of the fetus. Therefore, the hope that the behavior of the acquired diet to supplement the strong, can only supplement the fat. Fat does not equal strong. And this fattening up of fat often gives rise to other diseases. Pediatric leg pain manifests most often in the knee joint. Some also spread upward to the thighs or downward to the calves. Some also have ankle joints. All recover with rest. Therefore, treatment of knee pain in children is simple and can be self-healing with cold compresses and rest (cold compresses can reduce pain). Do not use plasters, massage, bruising type of medicine and wine application, spray, physiotherapy (heat therapy), closure, cupping, acupuncture, etc. It will aggravate the pain and prolong the pain. There is only one type of idiopathic knee pain. If a child is active in a cold-air environment during the day, there is a risk of injury to the respiratory tract by cold air, causing an inconspicuous upper respiratory tract infection. The infected bacteria travel with the blood to the injured knee, causing conditions such as redness, swelling, heat and pain in the joint, and more likely secondary to a build-up of pus in the knee. This kind of knee pain is not something that can be recovered by sleeping on it. Hospitalization is required.