Suspect ankylosing spondylitis in anyone with chronic or recurrent low back pain, fatigue, and stiffness, especially if: - 45 years or younger, - back pain present for more than 3 months, - back pain and stiffness in inflammatory and worse in the morning, improving with movement, - Current or previous: buttock pain, pain in the thoracic or cervical spine, arthritis, enthesitis, anterior or uveitis, psoriasis or inflammatory bowel disease or genitourinary infection.