The 4-character test, also known as the pan leg test and the hip abduction and external rotation test, is a common clinical examination, mainly applicable to the examination of large joints with intermittent or continuous pain or joint stiffness and restricted movement, and is one of the examination methods for sacroiliac joint and hip lesions. The examination is performed with the patient lying on his back with one leg straight and the other leg bent at the hip and knee so that the foot is close to the other leg that is straight. The examiner presses the patient’s pelvis with one hand and presses the bent knee with the other hand so that the knee is as close to the bed surface or the floor as possible. If there is pain in the sacroiliac joint, this is a positive indication of a lesion in the sacroiliac joint.