Ultrasound, x-ray, CT and MRI are available to examine the knee joint, but the specific type of examination to be done depends on the clinical symptoms of the knee joint or the history of the disease in question. For example, if there is an obvious external injury or a suspected fracture, the priority is to have an x-ray, and the specific results of the x-ray will determine whether a CT test is needed. However, if ligament damage, meniscal damage, joint effusion or other related problems are suspected, MRI should be done. If you initially suspect a lesion such as a popliteal cyst, you can give priority to a cheaper ultrasound examination, although an MRI can also be done to see it. Therefore, it is not intuitive to determine what exactly should be done for a knee examination, but rather a comprehensive judgment based on the relevant clinical symptoms, medical history, and characteristics, and the focus of different examinations on the disease is different.