Spondyloarthritis (SpA) is a type of arthritis that involves joints along the spine as well as hips, shoulders, knees and ankles.
When there is arthritis in a joint, it can be warm and swollen and painful to move or tender to touch. These problems are a direct result of the inflammation in the joint. When the arthritis is in a large, deep-seated joint, such as the hip or along the spine, the swelling can be difficult or impossible to see on physical exam and requires use of radiology imaging such as CTs or MRIs. In SpA, an additional location in the body where inflammation often occurs is where tendons attach our muscles to bones, or where ligaments attach to bones (these areas are called enthesis; plural entheses).
SpA can occur in children and adults. There are many forms of SpA. The most advanced form of SpA is known as ankylosing spondylitis (AS). In patients with AS it is required that there is evidence of involvement of the spine on X-ray. When this occurs in children it is called juvenile ankylosing spondylitis (JAS). A far more common type of SpA in children is called enthesitis-related arthritis (ERA). Additional information about ERA is provided below and in the information about juvenile idiopathic arthritis.
SpA usually develops in people who are 20-30 years old, but one out of every six or seven cases begins in the teenage years. If you haven’t developed AS by the time you’re 45, chances are good that you won't. Although the exact number of individuals with SpA is not known, it occurs in about five to nine out of every 1,000 people. Since about half of these people have AS, there are close to 500,000 cases in the United States alone.