Recently, I met many parents who brought their children to the clinic for leg pain, and they were diagnosed with “synovitis” in outside hospitals. Some of them are 7 or 8 years old children who walk with a limp for some reason, but the examination says they have knee pain. They came to our hospital, and after careful examination, the pain was actually in the hip joint, and after taking an orthopantomogram of the pelvis, they considered “ischemic necrosis of the femoral head”. Some of them were 13 or 14 years old, fat, and felt knee pain after one exercise. He came to the outpatient clinic and had a careful examination of the hip joint pain, and the X-ray showed “slipped femoral epiphysis”, which was quite serious because of the delay in diagnosis. The child complained of knee pain, do not forget to ask or check the hip joint; 2, if the pain is more than three weeks, often not synovitis.