A Swollen Pediatric Joint

A 6 year old girl with a swollen right knee in the absence of trauma, fever, rash or lymphadenopathy. Symptoms are worse in the early morning, and improve throughout the day. She also complains of eye pain. What is the diagnosis?

Juvenile Idiopathic Arthritis (oligoarticular type)


Arthritis in children is not uncommon. When encountered by pediatricians, it is characterized into one of three subtypes: systemic, oligoarticular, and polyarticular.

• The oligoarticular type is the most common. Usually occuring around 5 years old, it is seen in the large joints (but not the hips) and is known for it's casual but unique association with uveitis (irritation of the eye) and a positive ANA (an antibody in the blood). If left untreated, this uveitis can lead to glaucoma when they are older.

• The polyarticular type is the second most common, and usually affects the large and small joints on both sides symmetrically. Older children with bloodwork that is rheumatoid factor positive are likely to progress to arthritis as adults.

• The systemic type is often easiest to recognize, as an adolescent will often present with fever, a salmon-colored rash, and lymphadenopathy. Many different joints can be affected, and treatment requires disease-modifying drugs (DMARDs). Untreated systemic JIA can progress to a dangerous condition known as macrophage activating syndrome. 

The disease is manageable when caught early, and is typically managed by a specialist known as a rheumatologist. An early step is be sure the swelling isn't the result of an athletic injury or fall. The pediatrician will be sure to rule out more serious causes such as a septic (infected) joint.