Glossary of AS Terms

Last updated: May 2019

Ankylosing spondylitis

A chronic inflammatory arthritis that commonly affects the spine, although other joints in the body may also be affected, causing pain and stiffness.


Abnormal stiffness or fusion of a joint.

Bamboo spine

If AS progresses and the spine becomes more immobilized by the formation of bone in the joints, the spine can take on the appearance of bamboo on x-rays.

Cauda equina syndrome

A rare but potentially serious complication that can occur in people with AS in which the nerves at the bottom of the spine become compressed, leading to motor and sensory problems for the legs, bladder, and bowel control.


(also called glucocorticoids or steroids)
Medications that mimic the hormone cortisol, which reduces inflammation in the body.


The locations where the ligaments and tendons attach to the bone.


Inflammation of the entheses.

Extra-articular complications

Problems or conditions caused by the chronic inflammation of AS that occur in parts of the body beyond the joints, such as skin, eye, or intestinal complications.


A neurological condition that causes widespread in the body; People with AS have a greater risk of developing fibromyalgia.

Fibrosis of the lungs

A possible complication of AS in which scar tissue forms in the connective tissue between the air sacs in the lung and causes shortness of breath.


A complication of AS in which the two bones of a joint become bonded together, causing stiffness and lack of mobility in the joint.


A genetic marker that has been identified as playing a role in the cause of AS; However, not everyone with the HLA-B27 mutation develops AS, and it is believed that many people in the general population have the HLA-B27 marker but will not develop the condition. In addition, some people with AS do not have the HLA-B27 marker.

Inflammatory bowel disease

A term used to describe several conditions that involve chronic inflammation of the digestive tract, including ulcerative colitis and Crohn's disease; people with AS have an increased risk of developing inflammatory bowel disease (IBD).

Juvenile-onset ankylosing spondylitis or juvenile ankylosing spondylitis (JAS)

AS that occurs in children or adolescents (before the age of 18).


An outward curvature of the spine which causes a hunched or rounded back that is a possible complication as AS progresses and damages the joints between the vertebrae.

NSAIDs or non-steroidal anti-inflammatory drugs

Widely used medications for pain and inflammation that are frequently used as a first-line treatment to help relieve the symptoms of AS.


A condition in which the bones are weakened and brittle and at an increased risk of fracture; AS puts at person at greater risk of developing osteoporosis.

Peripheral joints

Joints in the arms or legs that may be affected with AS, such as the hips or shoulders.


A chronic skin condition that causes raised, red, scaly patches on the skin, which may be itchy, painful, and can crack and bleed; psoriasis is a common extra-articular complication of AS.

Radiographic evidence

Signs of joint involvement from AS are visible on imaging such as x-rays or MRI.

Sacroiliac joints (SI joints)

The joints located between the bottom of the spine (the sacrum) and the ilium of the pelvis, which are frequently the first joints to have symptoms from AS.

Slow-acting anti-rheumatic drugs (SAARDs)

Medications that may be used to treat pain and inflammation of AS, also known as DMARD's (disease modifying anti-rheumatic drugs).


Inflammation of the spine.


(also called spondyloarthropathy, spondylitis or SpA)
A general term that encompasses several different arthritis conditions (including ankylosing spondylitis) that cause joint inflammation.


A possible complication of AS which is characterized by a narrowing of the spinal column that can cause pain or nerve damage.


Calcification of the spinal ligaments.

TNF inhibitor

A type of biologic therapy that blocks tumor necrosis factor (TNF), a naturally occurring protein that plays a role in the inflammatory process and is elevated in people with AS.


Inflammation in the eye that occurs in the uvea (the middle layer of the eye), causing redness, pain, sensitivity to light, blurry vision, excessive tears and visual loss; uveitis is a common complication among people with AS.

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