Pain in the root joint of the thigh can be caused by several reasons: first, necrosis of the femoral head, when there is necrosis of the femoral head, there can be pain in the root joint of the thigh, which can radiate to the inner side of the thigh and the front side of the knee, and the pain is very obvious when the hip joint is under weight. Second, aseptic inflammation of the hip joint, such as osteoarthritis of the hip joint, or synovitis due to rheumatoid or gout, can also have pain in the joint at the root of the thigh, which should be identified early to treat the cause early. Third, tumor diseases, when the hip joint bone, soft tissue or synovial membrane tumor, can lead to hip pain, then we should check the hip MRI and pathological examination to diagnose. Fourth, impingement syndrome, impingement syndrome of the hip joint can also lead to hip pain, especially when squatting and lifting the hip joint pain is very obvious, then we should check the hip joint X-ray, MRI to diagnose. Fifth, infectious diseases, when the hip joint has bacterial infection, tuberculosis infection or brucellosis infection, there can also be pain in the joint at the root of the thigh, often accompanied by joint effusion and symptoms of redness, swelling and pain, it is necessary to identify the pathogenesis of bacteria and MRI to diagnose and treat early.