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Arthritis refers to inflammation of a joint or joints that can lead to joint damage in the absence of diagnosis and treatment. 

Information about the normal joint is provided in pmm nursing.

There is a spectrum of conditions that can result in arthritis - the graphic below is a helpful reminder but not an exhaustive list. 

Arthritis can affect a single joint or multiple joints and can be a manifestation of many systemic conditions and processes (including infection, malignancy, connective tissue diseases, genetic conditions and other metabolic diseases). 

Clinical assessment and the presence or absence of red flags are most important when considering the differential diagnosis. The use of investigations and their judicious interpretation will help to confirm or refute potential causes. 

Single joint arthritis:

  • In the absence of trauma or infection (or Acute Rheumatic Fever in high risk populations), Juvenile Idiopathic Arthritis (JIA) is the most likely cause of a single swollen joint. In contrast to adults with a single swollen joint, children very rarely get gout.  Mycobacterial disease (including Tuberculosis [TB]) must always be considered with a single swollen joint in endemic areas or in a child with risk factors (immunosuppression or risk of exposure or with co-existent Human Immunodeficiency Virus). The corollary however, is that not all cases of chronic monoarthritis are due to TB.  Inflammatory bowel disease associated arthritis may precede or follow the gastrointestinal features. 

Multiple swollen joints:

  • There are many causes including systemic diseases such as rheumatic disease (JIA, connective tissue diseases, autoinflammatory diseases / periodic fevers), genetic diseases (e.g., sickle cell disease, Down's syndrome arthritis) and some metabolic conditions.
  • Infections (e.g., Arboviruses and Acute Rheumatic Fever) and some forms of reactive arthritis cause multiple joint arthralgia or arthritis.  ARF tends to affect multiple joints although a monoarthritis is also possible. 
  • Connective tissue diseases such as Juvenile Systemic Lupus Erythematosus or Juvenile Dermatomyositis are multisystem conditions that tend to cause joint pain (arthralgia) rather than joint swelling. Children with genetic conditions may also be prone to developing a spectrum of joint problems, ranging from hypermobility to inflammatory arthritis. Inherited metabolic conditions (including mucopolysaccharidoses) may manifest with complex multisystem involvement including joint abnormalities due to contractures or sometimes hypermobility. Skeletal dysplasias may result in bone or joint pain and deformity. They can be suggested by other features such as short stature, joint contractures and family history.

The photograph below shows a swollen right knee (due to oligoarticular JIA).

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