Ankylosing Spondylitis, Radiologic Perspective: Ankylosing spondylitis (AS) is a type of progressive arthritis that leads to chronic inflammation of the spine and the area where the spine joins the pelvis (sacroiliac joints). Symptoms and signs of ankylosing spondylitis include lower back pain and the loss of side-to-side movement in the lumbar spine. Radiographs aid in diagnosis and may show sacroiliitis, syndesmophyte formation, fractures, pseudoarthrosis, entheopathy, protrusion of the femur head into the pelvis, and progressive fibrosis. Treatment involves exercise and painkillers.