He is 5 years old and in recent months has been complaining of leg pain. He was taken to the hospital for a checkup and found out that the child had an osteoid osteoma, which required surgery. Bone pain is common in growing children, the most common being “growing pains”, which are intermittent episodes of pain in the knee or lower leg, usually at night, usually lasting for ten minutes, and can improve on their own without medication, with normal activity the next day. The pain may occur 3-4 times/month. Pain attacks are not accompanied by systemic symptoms such as fever or rash. However, there are some diseases that can show the same symptoms as “growing pains”, which are easy to ignore or even cover up the disease. Synovitis: children with synovitis of the hip or knee can also show bone pain in the lower limbs. However, the bone pain caused by synovitis is usually persistent, aggravated by activity, and generally has a limp. It often follows an upper respiratory tract infection. After the respiratory infection improves, the bone pain will then disappear. 2. Arthritis: Arthritis is sometimes confused with “growing pains” because young children cannot tell the difference between bone pain and joint pain. Arthritis can be classified as bacterial, viral, rheumatoid, or idiopathic, and some may have fever, red skin, swollen joints, and stiffness. 3, osteoid osteoma: This is a benign tumor that occurs in the long bones of the extremities, and can also manifest as pain at night. It requires surgery. 4.Children leukemia: Leukemia can also manifest as bone pain, which can be accompanied by fever, recurrent infections, anemia, and enlarged liver and spleen. Because the leukemia cells invade the bone marrow, it causes the bone marrow to proliferate and swell and the periosteum to be stretched, causing bone pain, especially the most pronounced below the knee. It is easily confused with growing pains. 5.Malignant osteoma: Malignant osteoma is also called bone cancer, such as osteosarcoma and Ewing’s sarcoma. In addition to bone pain, it may be accompanied by fever and soft tissue swelling. The lesion progresses rapidly, metastasis may appear early, and the prognosis is not good. Surgery and chemotherapy are required. Doctors remind parents that if a child has unexplained leg pain that lasts for a long time, accompanied by fever, swollen joints, and limited joint movement, they should take the child to a children’s hospital for a specialist examination and diagnosis in a timely manner to avoid delaying the child’s condition.