Spondyloarthritis can be broadly classified as axial or peripheral, depending on where symptoms are concentrated. Axial spondyloarthritis predominantly affects the spine and sacroiliac joints; there are two types:
- Radiographic axial spondyloarthritis, also known as ankylosing spondylitis (AS), features characteristic damage on imaging
- Non-radiographic axial spondyloarthritis is characterized by similar symptoms to AS but without signs of AS on imaging
Peripheral spondyloarthritis predominantly affects areas outside the spine or sacroiliac joints, and includes:
- Psoriatic arthritis, which typically features psoriasis and is characterized by swelling of small joints in the hands and feet
- Reactive arthritis, in which symptoms are triggered by an infection
- Enteropathic arthritis, a type of arthritis associated with inflammatory bowel disease
- Undifferentiated spondyloarthritis, in which symptoms of peripheral spondyloarthritis present without a clear classification
Juvenile spondyloarthritis presents in children 16 years and younger, and can predominantly feature axial or peripheral symptoms.