There are many causes of low back pain and SI joint pain or sacroiliitis pain is just one of them. There are certainly certain maneuvers that your doctor can do to examine you that may suggest that you have SI joint pain or SI joint dysfunction. Generally if you have low back pain that is off to the side, just after the mid line or on both sides after the midline, that’s certainly suspicious for SI joint pain. It does not cause you symptoms like sciatica, it is usually just localized to that one spot in the back. The gold standard would be to get a sacroiliac injection or SI joint injection, usually with x-ray guidance. There is not a perfect radiology test to let you know if you have SI joint dysfunction. You can certainly have a normal x-ray or a normal CAT scan or normal MRI but still have SI joint pain or SI joint dysfunction. If you think you have SI joint dysfunction, call your doctor and make an appointment.