X-rays are usually sufficient together with blood tests to diagnose Ankylosing Spondylitis. MRI and CT scans may be used for further investigation. I know sometimes not all the puzzle pieces seem to fit your condition. I had one patient who does not have stiffness but has X-rays to show they have AS, but his main complaint is feeling hot all over his body. This disease does not follow the textbook's description for symptoms one might experience.