Growing pains in children are a kind of pain in the lower extremities of preschool children with unknown causes, which is common in children aged 4 to 12 years with normal growth and development, and is most common before the age of 8 years. Growing pains are mainly intermittent pains in the lower extremities, mostly occurring in the evening before going to bed or at night when waking up, varying in severity, mostly dull pains, but also pinprick-like pains or even severe pulling pains. The pain is mostly in the knee joint, followed by the thighs and calves, or in front of the calf bone; the pain is irregular and intermittent, without wandering, without restriction of limb movement, without redness, swelling, heat and pressure pain, without fever, rash and other systemic symptoms, lasting from a few minutes to a few hours, with intervals ranging from several days to once every few days, weeks or months. Most of them can resolve on their own. The diagnosis of growing pain can be made if the following criteria are met: 1) transient intermittent limb pain or arthralgia that resolves on its own; 2) pain history of at least six months, with at least five episodes of pain; 3) pain at a fixed location without wandering, no abnormal local signs, and no restriction of limb movement; 4) clinical and laboratory tests that exclude other diseases causing limb pain. The exact cause of growing pain is not clear yet, because one of the characteristics of growing pain is that it is not painful during the daytime, and it is easy to attack at night when the daytime activity is high, so it is mostly thought to be related to excessive daytime activity of children; at night when children sleep, the secretion of growth hormone increases, and the epiphyseal cartilage and epiphysis grow faster than the periosteum and the pulling stimulates the periosteal nerve can also lead to pain. In addition, the lack of calcium, magnesium, zinc and other trace elements, delayed bone development, limb microcirculation disorders and psychological factors can be related to the growth pass. Growing pain is a temporary limb pain disorder that occurs before the most vigorous growth period of children, and it can completely heal on its own as growth and development mature. The disease is not a manifestation of real disease, heals well and does not require special treatment; however, attention should be paid to strengthening nutrition, especially calcium, zinc and magnesium supplementation; when the pain attacks can be relieved by means of language comfort, muscle massage and hot compresses, and if necessary, common pain medications can be taken orally. It is important to pay attention to the characteristics of pain attacks to distinguish them from leg pain caused by other diseases. The pain in the lower limbs caused by the following diseases is often accompanied by other clinical symptoms, and the pain will not disappear on its own, and will only be eliminated after clinical treatment. 1.Septic arthritis has a rapid onset, with severe pain in the knee joint, redness, swelling and heat in the joint, and restriction of joint movement, accompanied by high fever, chills and other symptoms of systemic infection. 2. Acute hematogenous osteomyelitis has a rapid onset, with persistent pain in the joint, impaired joint movement, and systemic symptoms of toxicity, such as headache, high fever, and chills. 3.Rheumatoid arthritis joint pain is not fixed, wandering, red, swollen, hot, with generalized fever, fatigue and weakness, etc. 4.Some children with acute lymphoblastic leukemia can have bone and joint pain as early manifestation due to the infiltration of leukemia cells that destroy the bone cortex, bone marrow and joints; it manifests as vague pain, soreness and occasionally severe pain in the sternum, humerus, shoulder, elbow, hip and knee joints; most children have irregular fever and hepatosplenomegaly. Most children have irregular fever and hepatosplenomegaly. If they do not know enough about it and are not vigilant, it will easily lead to misdiagnosis and mistreatment. In clinical cases where bone and joint pain is diagnosed as rheumatism or rheumatoid arthritis and the anti-rheumatic effect is not good, high vigilance, patient and careful physical examination, repeated blood smear and timely bone marrow aspiration examination should be performed. 5, joint pain caused by bone tumors, such as the most common malignant bone tumor osteosarcoma in children is most likely to occur in the femur, tibia, humerus and other long tubular bones, with the distal femur and proximal tibia, that is, around the knee joint is most common. The early symptoms are pain, which starts as vague pain and gradually develops into persistent and severe pain, especially at night, often waking up in sleep, which is known as “resting pain”. As the disease progresses, the pain is progressively aggravated, the pain site is fixed, and local swelling, skin shining, epidermal redness and swelling, surface varicose veins and elevated skin temperature gradually appear, and some children may have fever, poor appetite, anemia and other symptoms. The pain is unbearable and cannot be relieved by general painkillers; it often develops suddenly after mild trauma, and a local lump can be found in about a few weeks, with varying hardness, fast growth and mild pain; some patients can have pathological fractures, and the tumor is large and adjacent to the joint, which can affect the joint function. Since parents rarely associate bone tumor with children’s joint pain in early stage, and children are active, when joint pain occurs, it is easy for parents to mistake it as normal physiological phenomenon – growing pain, or think it is general sprain or arthritis, which delays the treatment and misses the best treatment opportunity. Therefore, when a child suddenly develops pain around the knee joint with unknown cause, which cannot be relieved after resting, and the pain worsens at night, he/she should go to a specialized hospital in time to exclude the possibility of bone tumor.