A 43-year-old man falls and presents with acute back and diffuse abdominal pain. He has had back pain on and off for years. Also, his wife notes that he has become “stooped” forward in the last few years. The radiographs show flowing ligamentous ossification and syndesmophyte formation about the cervical, thoracic, and lumbar spine consistent with ankylosing spondylitis (bamboo spine) (Figure 98-1). The KUB (kidneys, ureters, bladder) view film also shows fusion of the sacroiliac joints consistent with ankylosing spondylitis (Figure 98-2). No fracture, dislocation, or abdominal pathology is identified. The patient's symptoms are treated and nonsteroidal antiinflammatory drugs (NSAIDs) are started. On follow-up a blood test reveals that he is human leukocyte antigen (HLA)-B27-positive.