Knee pain first requires basic judgment by the clinician, as follows: 1, if the knee pain is caused by bruises, falls, etc., X-rays are preferred; 2, if the fracture is difficult to determine, or structural changes that require differential diagnosis, CT examination is required, which can clearly determine the fracture, especially occult fractures or microfractures; 3, if the fracture is okay and not obvious, but the patient’s symptoms are heavy. MRI should be selected for clear judgment if the knee meniscus or accessory structures such as cruciate ligament or collateral ligament are often considered to be damaged; 4. If the knee pain is caused by non-traumatic degenerative arthritis or suspected to be formed by an occupying lesion, the advantage of selecting MRI is greater than CT, but CT examination is not excluded for some special cases. Therefore, the clinician needs to make a clear judgment, treat it differently and choose flexibly.