uworld qid 19491 - patient with ankylosing spondylitis has lower back pain, bilateral buttocks pain and stiffness, has fatigue, lumbar spine and sacroiliacs painrful to deep palpation, elevated ESR, with stooped walking posture.
pateitns will have areas of bony erosions and new bone formation causing the stiff or bamboo spine.
inflammatory cytokines activate osteoclast precursors causing bony erosions -> secondary osteoporosis and compression fractures
during the reparative process, excessive new bone formation occurs filling the previously eroded sites manifesting as the bridging syndesmophytes in vertebral column (bamboo spine) makign the spinal ridgitity, postural alterations, and increased risk of fracture.