Different types of inflammatory arthritis

Rheumatologists divide inflammatory arthritis into 2 main types (though there are many others):

Rheumatoid arthritis (RA) where people who have symptoms of inflammatory arthritis, often involving the hands and feet, have antibodies called rheumatoid factor in their blood. This is often referred to as being rheumatoid factor or sero-positive.

Spondyloarthritis (SpA) where people who have symptoms of inflammatory arthritis, often involving the spine as well as other joints, do not have rheumatoid factor antibodies in their blood. These are also sometimes called seronegative SpA

The SPA family

Four different conditions make up the SpA family.

  • Ankylosing spondylitis
  • Enteropathic arthritis
  • Psoriatic arthritis
  • Reactive arthritis which is also known as Reiter's syndrome

In addition to these 4 conditions some people develop symptoms which strongly indicate that they have a SpA but which do not allow a clear cut diagnosis to be made. In this case the term undifferentiated spondyloarthritis (USpA) is used.

Ankylosing spondylitis (AS)

There is much more information on AS throughout the website. Click here to read about the main symptoms of AS or here to read our page on What is AS?

Enteropathic arthritis

Enteropathic arthritis is strongly linked with inflammatory bowel disease, particularly ulcerative colitis and Crohn's disease.

Around 10% of people with these conditions also develop arthritis. Click here to read more about these types of inflammatory bowel disease.

Enteropathic arthritis may affect any joint but often affects the feet, ankles and knees. As with other SpA, inflammation can occur in the spine generally and the sacroiliac joints in particular. Inflammation of the eyes (uveitis or iritis) can also occur.

Reactive arthritis

Reactive arthritis is also known as Reiter's syndrome. It develops as a reaction to an earlier infection. It is thought that reactive arthritis occurs when the immune system over-reacts to an infection and inflames healthy tissue in areas of the body including the joints, eyes and urethra.

The two most common types of infection linked to reactive arthritis are bowel infections and sexually transmitted infections. Reactive arthritis is quite different from other forms of arthritis which may be provoked by viral infection, such as hepatitis and parvovirus.  

The outlook for reactive arthritis is reasonably good, and most people's symptoms will get better within 3 to 12 months. Some people's symptoms will recur at some point in the future and in a small number of people the symptoms will persist.

Psoriatic arthritis

Psoriasis is a flaky skin condition which affects about 5% of the UK population to varying degrees. Some people with psoriasis also develop arthritis. This can vary from a relatively mild form of arthritis which affects 1 or 2 joints only to a very aggressive disorder causing widespread joint damage.

Some people also develop inflammation in the sacroiliac joints and spine as well as tendon attachments in the heels.

Undifferentiated spondyloarthritis (USpA)

Some adults and children develop arthritis which resembles a SpA but doesn't quite fit into any of the different family members. These people are then described as having an undifferentiated spondyloarthritis which is often shortened to the term USpA.

Last reviewed: May 2011