Lumbar protrusion is clinically known as lumbar disc herniation. The difference between sacroiliitis and lumbar disc herniation lies in the nature of pain, the presence of neurological symptoms, and the etiology. 1. The nature of pain: sacroiliitis and lumbar disc herniation can be manifested as low back pain, and their clinical manifestations are extremely similar. The pain caused by sacroiliitis usually does not radiate to other parts of the body and is mainly a dull ache. Lumbar disc herniation pain can radiate to the buttocks and lower limbs. 2. Whether there are neurological symptoms: sacroiliitis and lumbar disc herniation, compared with the general lack of neurological symptoms. Lumbar disc herniation often manifests as sciatica. 3. Etiology: sacroiliitis is usually caused by aging, infection, congenital structural abnormality, autoimmune disease, etc. Lumbar disc herniation is usually caused by degenerative changes of lumbar disc. If you have the above symptoms, you should go to the hospital in time for the relevant examination, and make clear the cause of the disease and targeted treatment.