May also be called: AS; Rheumatoid Spondylitis; Spondylarthroarthritis Ankylosing spondylitis (ang-kih-LOH-sing spon-duh-LIE-tis) is a chronic (long-term) type of arthritis that causes inflammation in the joints of the spine and the pelvic bones. More to Know "Ankylosing" means joining together, and "spondylitis" means inflammation (pain and swelling) in the vertebrae (the bones that make up the spine). AS causes inflammation in the joints in the spine and between the spine and pelvis. As part of healing, the body can form new bone. This may cause vertebrae to become fused together, leading to a less flexible spine. Some people with AS can have inflammation in other joints, the eyes, and rarely even in the heart and lungs. Doctors don't know what causes AS, but there is a strong genetic association. It usually begins in the late teen years or young adulthood. The signs and symptoms of AS may get better or worse from time to time, but it is a lifelong condition. Back pain and stiffness, joint pain, swelling, fatigue, and a hunched posture are common symptoms. Treatment involves medications and exercises to relieve symptoms and keep the back as strong and flexible as possible. Keep in Mind There is no cure for ankylosing spondylitis, but starting treatment as early as possible can help control pain and minimize complications. All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts. Back to Articles Related Articles Word! Joints Joints are the places in your body where bones meet. Read More Word! Arthritis This is what happens when joints - the places where bones meet - get painful, swollen, and stiff. Read More Arthritis Kids can get a kind of arthritis that causes joint pain. Find out more in this article for kids. Read More A to Z: Spondylolisthesis Spondylolisthesis (or "slipped vertebra") is when one of the vertebrae slips forward and out of place on the vertebra beneath it. Read More A to Z: Spondylolysis Spondylolysis is when there is a defect of a narrow piece of bone in the vertebra. Read More Getting an X-ray (Video) You'll get an X-ray if your doctor thinks you might have a broken bone. Find out how X-rays are done in this video for kids. Read More Magnetic Resonance Imaging (MRI): Lumbar Spine A lumbar spine MRI is a painless test that uses a magnetic field and radio waves to produce detailed pictures of the bones, disks, and other structures in the lower back. Read More Juvenile Idiopathic Arthritis (JIA) Learn about juvenile idiopathic arthritis, a specific kind of arthritis that usually occurs in kids and teens younger than 17. Read More Bones, Muscles, and Joints Without bones, muscles, and joints, we couldn't stand, walk, run, or even sit. The musculoskeletal system supports our bodies, protects our organs from injury, and enables movement. Read More Juvenile Idiopathic Arthritis In juvenile idiopathic arthritis (also called juvenile rheumatoid arthritis)), a person can develop swollen, warm, and painful joints. Learn more. Read More Fibromyalgia The chronic condition fibromyalgia causes widespread pain in the muscles, joints, and other areas of the body. Lifestyle changes and other strategies can help kids who have it feel better. Read More Fibromyalgia Fibromyalgia is a long-term condition that causes pain in a person's muscles, joints, and other soft tissues. Find out how doctors tell if a person has fibromyalgia and what can be done to treat it. Read More Bones, Muscles, and Joints Our bones, muscles, and joints form our musculoskeletal system and enable us to do everyday physical activities. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.