Sudden pain at the root of the thigh can be caused by the following reasons: first, hip impingement syndrome, patients with hip impingement syndrome can have a tear in the glenoid labrum after impingement, resulting in pain in the hip joint, which requires early examination of MRI and X-ray of the hip joint for early diagnosis and treatment. Secondly, infectious diseases of the hip joint, such as bacterial infection or tuberculosis infection, may cause sudden pain at the root of the thigh, accompanied by fever and other systemic symptoms, and early examination of the MRI and blood tests of the hip joint is necessary for early diagnosis and treatment. Third, femoral head disease, when the femoral head has necrosis can also appear sudden pain at the root of the thigh, especially when walking pain is very obvious, then the early examination of the femoral head MRI to early diagnosis. Fourth, gout, when gout involves the hip joint, sudden pain at the root of the thigh can also occur, then early blood uric acid tests and hip x-ray should be taken for early diagnosis.