Medical professionals coined the umbrella term spondyloarthritis (pronounced spawn-dee-LOW-arth-RI-tis, also known as SpA) in the 1970s to describe several related diseases, including but not limited to ankylosing spondylitis, psoriatic arthritis, and reactive arthritis.1,2 In 2009, two new classification terms were introduced: axial spondyloarthritis (axial SpA) and peripheral spondyloarthritis (peripheral SpA).
The new terms do not replace the traditional, specific spondyloarthritis diagnoses (e.g. ankylosing spondylitis). Instead, these terms allow doctors to:
- Classify existing spondyloarthritis patients according to which joints are affected: the axial joints of the spine or the peripheral joints of the arms and legs. Classifying patients this way can be helpful when doctors design treatment plans, for example.
- Recognize and diagnose spondyloarthritis in people who are experiencing early symptoms but who may not yet meet all the diagnostic criteria for a traditional, specific spondyloarthritis.
Early diagnosis and treatment tend to lead to better short- and long-term health outcomes.
Traditional Spondyloarthritis Classifications
Medical professionals make distinctions between different types of spondyloarthritis:
Ankylosing Spondylitis (AS) causes inflammation, stiffness, and pain in the spine.
Enteropathic Arthritis (EnA) causes back and/or joint pain as well as intestinal inflammation associated with conditions such as Crohn’s, ulcerative colitis, and undifferentiated colitis.
Psoriatic Arthritis (PsA) causes pain in the small joints of the hands and feet and/or larger joints, such as the knee. It is associated with a skin condition called psoriasis.
Reactive Arthritis (ReA) can cause inflammation and pain in the joints, skin, eyes, bladder, genitals, and mucus membranes. Reactive arthritis typically follows an intestine or urinary tract infection or sexually transmitted disease and may be temporary—lasting 2 to 12 months—or chronic.
Juvenile Spondyloarthritis (JSpA) is the diagnosis given to children who have spondyloarthritis symptoms.
Undifferentiated Spondyloarthritis (USpA) is a classification used for people who have spondyloarthritis symptoms that do not fit into another category of SpA.
In time, the term undifferentiated spondyloarthritis will probably disappear, and patients will be classified as either having peripheral spondyloarthritis or non-radiographic axial spondyloarthritis.
Newer Spondyloarthritis Classifications
The Assessment of SpondyloArthritis International Society now classifies cases of spondyloarthritis into two main categories: axial spondyloarthritis and peripheral spondyloarthritis.
1. Axial Spondyloarthritis (AxSpA) is a condition causing painful inflammation in the spine and/or the sacroiliac joints, which connect the spine to the pelvis. There are two types of axial spondyloarthritis:
- Radiographic spondyloarthritis causes joint changes that can be seen on an X-ray.
- Non-radiographic spondyloarthritis causes joint changes that cannot be seen on X-ray.
A person who has non-radiographic spondyloarthritis may or may not eventually develop radiographic spondyloarthritis.3 Not all doctors agree that it is helpful to make a distinction between radiographic and non-radiographic spondyloarthritis.4
According to the CDC, 2.7 million adults in the United States have some type of axial spondyloarthritis.5
2. Peripheral Spondyloarthritis (pSpA) causes inflammation in joints other than the spine or sacroiliac joints. People with peripheral spondyloarthritis may experience painful inflammation in the hands, wrists, elbows, shoulders, knees, ankles, feet, or other joints.
These newer classifications are umbrella terms that include all the conditions listed under traditional classifications. Traditional and newer classification systems are often used together.
So What Do I Have?
Axial and peripheral spondyloarthritis may be used as stand-alone diagnostic terms or may be used to help describe the traditional diagnostic terms. For example:
- People who have ankylosing spondylitis almost always have axial radiographic spondyloarthritis.
- People who have psoriatic arthritis typically have peripheral spondyloarthritis, especially initially.
- People who have other types of spondyloarthritis, such as reactive arthritis, may have either axial or peripheral spondyloarthritis.
- People might receive a diagnosis of axial spondyloarthritis or peripheral spondyloarthritis without a more specific disease diagnosis.
Because symptoms change over time, a person may have peripheral spondyloarthritis and develop axial spondyloarthritis, or vice versa. In addition, some people may have both axial spondyloarthritis and peripheral spondyloarthritis.
Getting an accurate spondyloarthritis diagnosis is important, because it helps ensure a patient’s treatment adequately addresses his or her symptoms.
- Rudwaleit M, van der Heijde D, Landewé R, et al. The development of Assessment of SpondyloArthritis international Society classification criteria for axial spondyloarthritis (part II): validation and final selection. Ann Rheum Dis 2009;68:777-83.
- Rudwaleit M, van der Heijde D, Landewé R, et al. The Assessment of SpondyloArthritis International Society classification criteria for peripheral spondyloarthritis and for spondyloarthritis in general. Ann Rheum Dis 2011;70:25-31.
- Baraliakos X, Braun J. Non-radiographic axial spondyloarthritis and ankylosing spondylitis: what are the similarities and differences?. RMD Open. 2015;1(Suppl 1):e000053.