Pain in the joint between the thigh and the buttock, also known as hip pain, can be caused by the following reasons: First, inflammation, when the hip joint has aseptic inflammation due to rheumatism, rheumatoid or osteoarthritis, hip pain can occur, due to bacterial infection or tuberculosis bacillus infection, which can also lead to pain in the hip joint. Second, tumor, when the soft tissue or bone of the hip joint has tumor, it can also lead to hip pain. Third, impingement syndrome, when the acetabulum of the hip joint and the neck of the femur, or the sciatic bone and the small femoral ridge, can lead to pain in the hip joint, often when walking or lifting the leg pain is very obvious. Fourth, femoral head necrosis, femoral head necrosis can also lead to pain in the hip joint between the thigh and the buttocks, which should be examined by MRI and CT of the femoral head for diagnosis and early treatment.