An 8-year-old girl complained of intermittent episodes of pain in the left groin and left knee for nearly a week. After examination, I considered the possibility of hip synovitis and advised her to go to the Department of Orthopedics and Traumatology of Pediatrics for immediate examination to avoid delaying treatment. The diagnosis and western medical treatment of hip synovitis in children is the strong point of the corresponding specialty in children’s hospitals. For children with hip synovitis, early diagnosis and early treatment are very important. The possibility of hip synovitis should be considered when the child has the following three conditions: 1. under 10 years of age; 2. unexplained acute or chronic pain in the hip joint area, with the pain worsening at night; 3. symptoms of limping or limited knee movement. It is worth noting that although the lesion of the disease is in the hip joint, some children with the disease may have symptoms of knee pain, which is a radiating pain caused by the inflammatory response of hip synovitis that irritates the patient’s closed foraminal nerve. The cause of the disease is not well understood, but it is generally believed to be a nonspecific inflammatory disease caused by an immune response or allergy, associated with viral infections, bacterial infections, and trauma. Children often have a history of upper respiratory tract infections, such as colds, within 1 to 2 weeks prior to the onset of the disease. The duration of the onset of hip synovitis in children is often divided into 3 phases: Phase 1: acute onset, which can last from 1 to 7 days. The child presents with pain in one hip joint, which is intermittent and worsens at night. A small number of children with this disease may have knee pain, but no significant limp when walking. When the doctor presses deeply on the hip joint area, the child feels pressure and pain, and the pain is obvious when the hip joint is flexed and abducted. Stage 2: This stage of the disease can last for 8-40 days. Compared with stage 1, each pain attack lasts longer and a significant limp is seen when the child walks. During the physical examination, it can be found that the hip joint area of the child is full and the pressure pain is obvious; the child’s affected limb is different from the normal limb when it is flexed, abducted and externally rotated, and there is deformity, and the 4-character test is positive. Stage 3: The condition of this stage can last 40-90 days. The pain of the child in this stage is very severe and cannot be relieved even with rest. The child may develop hip flexion, limp or be afraid to move around. The early signs and the results of x-rays and laboratory tests performed on children with hip synovitis are very similar to those of patients with tuberculosis, rheumatoid arthritis and rheumatoid arthritis, making the disease very easy to misdiagnose. If the child is neglected or misdiagnosed with the disease, the child will continue to exercise as usual, which can lead to ischemic necrosis of his or her femoral head. When treating children with hip synovitis, it is important to first identify the stage of the disease and then treat the child differently. Children in stage 1 of the disease can be treated with small doses of oral non-steroidal anti-inflammatory drugs (e.g. aspirin) or herbal medicine. Such children are generally not strictly restricted in their activities, which will not aggravate their disease but will facilitate their recovery. Children in stage II of the disease can be treated with medication plus traction. In addition to medication, the child must be kept in bed and rested while traction is applied to the affected limb to relieve muscle spasm and reduce pain. The weight of traction should be 0.5-2 kg, and the pain can be relieved by traction for 2 to 5 days. After the pain is relieved, the child can do relatively light activities in bed. After removal of traction, the child can gradually practice walking. For children in stage III of the disease, medication and traction therapy should be continued, and the duration of traction can be extended to 4 weeks. The child should also be encouraged to do more muscle contraction exercises on the affected limb, which should be supplemented with massage to prevent muscle atrophy or reduce the symptoms of muscle atrophy. After the femoral head of the child has recovered its normal shape, the child can be allowed to practice walking with the help of crutches. If the above treatment is not effective, hip arthroscopy can be considered to clean up the inflammatory tissues in the joint by performing synovectomy. In children with ischemic necrosis of the femoral head, small-diameter, multi-orifice borehole decompression therapy may be performed. In general, children who are diagnosed and treated during the first and second stages of the disease are usually cured and recurrence is rare. If the child’s condition has progressed to stage III of the disease, or even to ischemic necrosis of the femoral head, treatment will be more difficult.