From a patient with low back pain who was complained about a sacroiliac MRI! Recently, I encountered a patient with low back pain in the clinic, and after repeatedly explaining his condition, I was given an MRI of the sacroiliac joint, but in the end, the patient complained. In fact, I wanted to write something a long time ago, but I have not acted due to my busy schedule, so today I take this opportunity to say something. Eighty percent of people experience back pain during their lifetime. Many people rest for a few days or take some medicine to get well, some people are repeatedly well again and again, a few people are trying to do everything possible, see all the major hospitals never good. Why is this? Please listen to my detailed explanation. There is a jargon called “patient back pain, doctor headache!” This explains the complexity of low back pain. There are hundreds of known causes of low back pain, of course, most of the causes of low back pain are waist problems, but there are also some low back pain problems not in the waist, but in the pelvis, sacroiliac joints, hip joints, and even visceral reasons, brain problems! There are many causes inside the waist that cause low back pain: there are lumbar fractures, tumors, infections, herniated discs, etc. that need to be dealt with as soon as possible. There are relatively not very urgent: lumbar sprain, disc degeneration, lumbar small joint-derived lumbar pain, lumbar slippage, sacroiliac joint lesions, spondylolisthesis. There is even nonorganic back pain in which the anatomical structure cannot be found to be wrong. The causes of low back pain outside the back are: abdominal lesions such as kidney, ureteral stones, pancreatitis, abdominal aortic aneurysm, pelvic inflammatory disease in women, prostatitis in men, and even mental factors such as anxiety and depression can also cause low back pain. It can be seen that there are many causes of low back pain, and each kind of low back pain has certain characteristics, so when you see a doctor, based on the patient’s description and situation, you can initially determine what causes of low back pain are more likely, and then give the corresponding examination, in order to most likely identify the cause of low back pain, instead of taking lumbar films for all patients with low back pain. Moreover, X, CT and MRI are useful for their own purposes, not that CT is unnecessary after MRI, or MRI is unnecessary after CT. In clinical practice, we often encounter patients with low back pain who come in and say that the doctor wants to do an MRI for me because of a herniated disc. Many patients can have a general judgment based on what they say, so that they know what tests they are suitable for and what part of the body should be investigated. Therefore, it is better for patients to have some understanding of their back pain, or it should be more beneficial to follow the doctor’s advice if they cannot understand it.