Oligoarticular arthritis, also called oligoarthritis, is the most common and mildest form of juvenile idiopathic arthritis (JIA). It’s also called oligoarticular juvenile idiopathic arthritis.

The term “juvenile” means that it develops in children or teenagers under age 16 years. The term “idiopathic” means the cause isn’t fully understood. Researchers think it might develop when genetically prone individuals come into contact with environmental triggers that cause an autoimmune reaction.

Oligoarticular arthritis is characterized by pain and swelling in a few joints, such as your:

  • knees
  • elbows
  • ankles

Medication can often reduce the immune reaction and help improve the condition, but some children may continue to have long-lasting symptoms.

Let’s examine oligoarticular arthritis in more detail, including symptoms, causes, and treatment options.

Oligoarthritis typically causes symptoms that last at least 6 weeks and affect between one and four joints, according to a 2022 study. The study notes that the knee is the most commonly affected joint. The ankles are also commonly affected.

Your child may have joint symptoms like:

Some people with oligoarthritis also develop fatigue or chronic uveitis. Uveitis is inflammation in the middle layer of your eye. It can cause symptoms like:

It’s important to diagnose and treat uveitis to prevent permanent vision loss.

About 2 in 5 children with persistent oligoarthritis experience moderately stunted growth. Persistent oligoarthritis means they have had symptoms for more than 6 months.

The exact cause of JIA isn’t clear, but symptoms may develop when your child’s immune system attacks healthy cells in their joints. About half of all JIA cases are oligoarthritis.

Genetics is thought to play a large role in the development of JIA. Certain infections may also contribute to its development in genetically susceptible children. Research is still inconclusive, but studies are examining the potential role of:

Risk factors for oligoarthritis include being female and under age 6 years.

Potential environmental factors that may increase the risk of JIA include antibiotic exposure and C-section delivery.

Factors that lower the risk may include breastfeeding and having household siblings.

Children with JIA can develop:

  • one leg that’s longer than the other
  • structural irregularities in the joint
  • short stature

A potentially serious complication is macrophage activation syndrome (MAS), which may occur in up to 10% of children with JIA. MAS is an overwhelming full-body inflammatory reaction that can lead to organ damage and may be life threatening.

It’s important to seek medical attention if your child has unexplained joint symptoms like pain or swelling, or if they experience changes in their vision. If your doctor suspects JIA, they might refer you to a specialist called a pediatric rheumatologist.

Your child may develop these symptoms for many reasons, but receiving a proper diagnosis can make sure they get treatment as soon as possible if they need it. Delaying treatment for JIA may decrease your child’s response to medications.

Your child’s doctor will likely start the diagnostic process for oligoarthritis:

  • with a physical exam
  • with a review of your child’s personal and family medical history
  • by asking your child about their symptoms

If JIA is suspected, the doctor may order blood tests to examine or look for:

Imaging can provide the doctor with supportive evidence to confirm the diagnosis. Your child might receive:

Treatment for oligoarthritis aims to reduce your child’s inflammation and prevent long-term joint damage. Most children receive medications, such as:

Other treatment options include:

  • nutritional support to support joint and eye health
  • physical therapy
  • surgery
  • routine eye care with an optometrist or ophthalmologist

Disability is rarer with oligoarthritis than with other subtypes of JIA. Receiving an early diagnosis can lessen joint damage and complications. Some children with JIA have symptoms for only months, while others have symptoms that persist into adulthood.

In a 2019 study, researchers found that 48.8% of people with JIA went into remission without the continued need for medication. An additional 49.9% achieved remission while continuing to take medications. Only 1.78% didn’t respond to medication and died of MAS.

It’s not known how to prevent oligoarthritis. Receiving early treatment can potentially reduce joint damage and lessen your child’s symptoms.

Here are some frequently asked questions people have about oligoarthritis.

What is the difference between polyarthritis and oligoarthritis?

Polyarthritis isn’t a specific type of arthritis. Instead, it means that five or more of your child’s joints are affected. Oligoarthritis affects four or fewer joints during the first 6 months of the condition.

How many joints does oligoarthritis affect?

Oligoarthritis affects four or fewer joints during the first 6 months of the disease. It’s referred to as persistent oligoarthritis if symptoms last longer than 6 months and extended oligoarthritis if lasts longer than 4 months and affects more than four joints.

Can adults get oligoarthritis?

By definition, oligoarthritis and other forms of JIA begin before age 16 years.

Oligoarthritis is a form of arthritis that affects children and teenagers under age 16 years. It can cause pain and swelling in between one and four joints, most commonly in your knees or ankles.

It’s thought that oligoarthritis is caused by an autoimmune reaction in genetically prone children. Medications to reduce immune system activity can potentially reduce symptoms and may improve the course of the disease.