Image of the Month

The vague presentation of ankylosing spondylitis often delays diagnosis. Affected patients are usually younger than 45 years of age and report low back pain with morning stiffness. Pain may alternate between buttocks and typically improves with movement—symptoms incorrectly attributed to nonspecific low back pain. To learn how MRI may help diagnose ankylosing spondylitis earlier, see Image of the Month, p. 22.