This article reviews the six types of spondylitis according to its traditional classification system.
Classification Systems
Spondylitis is classified by two different systems:
Traditional SpA: Recognizes six related, but separate forms of arthritis, including ankylosing spondylitis, enteropathic arthritis, juvenile spondyloarthritis, psoriatic arthritis, reactive arthritis, and undifferentiated spondyloarthritis. Newer SpA: Includes two broader categories that encompass all types of SpA, including two new classification terms, axial spondyloarthritis and peripheral spondyloarthritis.
The new classification allows healthcare providers to recognize and diagnose the condition in people who are experiencing symptoms but do not yet meet the diagnostic criteria for one of the traditional spondylitis types.
Spondylitis Types
Under the traditional classification system, there are six types of spondylitis.
Ankylosing Spondylitis (AS)
Ankylosing spondylitis (AS) is the most common type of spondylitis. AS causes inflammation, pain, and stiffness in the spine. The primary symptom of AS is gradual-onset chronic back pain that typically begins before the age of 45.
AS-related pain typically improves with activity but worsens with rest. Many people with AS experience pain and stiffness in the morning that gradually goes away with movement.
Over time, new bone formation in the spine can cause the spine to fuse, affecting a person’s mobility. AS may also cause pain and inflammation in other parts of the body, including the hips, shoulders, heels, and other joints.
Psoriatic Arthritis (PsA)
Psoriatic arthritis (PsA) is a chronic inflammatory disease that causes pain in small and large joints throughout the body, primarily in the hands, feet, and knees.
PsA can affect people at any age, but symptoms most often begin between the ages of 30 and 50.
Many people with PsA also have a skin condition called psoriasis, which causes red, itchy, or scaly patches often found on the elbows, knees, scalp, and trunk. Some people with PsA may experience dactylitis, or “sausage digit," a toe or finger with swelling between and around the joints.
Reactive Arthritis (ReA)
Reactive arthritis (ReA) is a form of inflammatory arthritis that occurs in reaction to a bacterial infection in the intestine or urinary tract.
ReA is a painful condition that causes inflammation in the joints, most commonly the ankles, fingers, heels, knees, lower back, and toes. Some people may also experience eye irritation or redness, a rash on the palms of the hands and soles of the feet, and joint pain.
ReA is temporary and often goes away on its own or with treatment within three to 12 months. However, the condition can recur, and some people with ReA may go on to develop another form of chronic arthritis. ReA most often occurs in men between the ages of 20 and 50.
Enteropathic Arthritis (EnA)
Enteropathic arthritis (EnA) is a chronic, inflammatory form of arthritis associated with inflammatory bowel disease (IBD). Approximately 1 in 5 people with Crohn’s disease and ulcerative colitis develop enteropathic arthritis.
EnA commonly affects joints in the limbs (arms and legs) and many people with the condition also experience back pain. In addition to joint pain, symptoms of EnA include abdominal pain, chronic diarrhea, bloody stool, and weight loss.
Undifferentiated Spondyloarthritis (USpA)
Undifferentiated spondyloarthritis (USpA) is diagnosed when people have spondyloarthritis symptoms but do not fit in another category of SpA.
For example, a person may have symptoms such as heel pain and psoriasis but no back pain or intestinal symptoms present in other forms of spondylitis. Over time, most patients will be diagnosed as having either peripheral spondyloarthritis or non-radiographic axial spondyloarthritis.
Juvenile Spondyloarthritis (JSpA)
Juvenile spondyloarthritis (JSpA) is a form of arthritis that occurs in children and adolescents.
JSpA symptoms include inflammation, joint pain, and fatigue. It most commonly affects joints in the lower part of the body, including the ankles, hips, knees, and pelvis. Enthesitis (inflammation where tendons and ligaments connect to bone) is a common symptom.
JSpA can also be associated with inflammatory bowel disease, which causes inflammation in the digestive tract. It is common for symptoms to come and go. The flare-up and remission cycle often repeats without an obvious cause.
Axial Spondyloarthritis vs. Peripheral Spondyloarthritis
Under the general umbrella term of spondyloarthritis, conditions are now classified further into two categories based on where symptoms occur in the body. These new classifications help healthcare providers make a more accurate diagnosis and provide more targeted treatment.
Based on the primary symptom a person experiences, people with SpA are divided into these two groups:
Axial spondyloarthritis (axSpA): This form of spondylitis most commonly affects the spine and pelvic joints. Back pain and stiffness of the spine are the predominant symptoms of axSpA. Axial spondyloarthritis is a broad category that includes people who may or may not have bone and joint damage detected by imaging tests. Peripheral spondyloarthritis (pSpA): This form of spondylitis commonly causes joint inflammation and pain outside of the spine and sacroiliac joints, including the ankles, hands, elbows, feet, knees, shoulders, and wrists. pSpA may also cause inflammation in tendons in the hands and feet (dactylitis) and where ligaments and tendons connect with bone (enthesitis).
Summary
Spondylitis is an umbrella term used to describe several different types of inflammatory arthritis that have similar characteristics and symptoms. Most forms cause back pain and inflammation. Talk to your healthcare provider if you have symptoms of spondylitis. Getting an early and accurate diagnosis can help ensure you get the proper treatment to reduce symptoms and avoid potential health complications related to the disease.
A Word From Verywell
Spondylitis is a chronic and often painful condition that can have a tremendous impact on your quality of life. Fortunately, early diagnosis and proper treatment can help reduce symptoms and prevent disease-related health complications. With the right treatment, many individuals living with spondylitis are able to live a full, happy life.
