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also have polyarthritis or arthralgia, colicky abdominal pain, and nephritis. As
with the rash, periarticular swelling usually involves joints below the waist.
Chronic arthritis is less common than acute arthritis in children younger than
age 16 years, with an incidence of 20 to 150 cases per 100,000. JIA is a newer
term used to classify chronic childhood arthritis. This term describes children less
than 16 years of age with joint inflammation for at least 6 weeks, in whom other
causes have been eliminated, and encompasses all of the diseases referred to as
JRA, as well as other causes of idiopathic arthritis. Subclassifications of disease
are based on the patient’s age at onset of symptoms, duration and pattern of
arthritis, and presence or absence of systemic signs such as fever or rash. Tests for
rheumatoid factor or ANA may assist in establishing a specific diagnosis. Since
JIA has a highly variable presentation, it appears at many different points in the
diagnostic algorithm. These are difficult diagnoses for ED clinicians to establish
based on a single patient encounter. Children with chronic arthritis should be
referred to a rheumatologist (see Chapter 101 Rheumatologic Emergencies ).
In the absence of fever, chronic pain of one or more joints may also indicate
malignancy. Specifically, leukemia or neuroblastoma can both present with true
joint swelling, as can bony tumors. Pallor, adenopathy, weight loss, and other
constitutional complaints, as well as anemia or cytopenias, would support this
diagnosis.
A large joint oligoarthritis occurs as an extraintestinal complication of
inflammatory bowel disease in about one-third of children, usually during times
of active disease. Clues to the diagnosis include abdominal pain, hematochezia,
anemia, and weight loss.
In summary, this review of joint pain in children should serve as a guide to the
diagnostic evaluation. The clinician must choose from many different causes,
each with variable and nonspecific characteristics. In addition, laboratory studies
are rarely specific for a particular disease. However, by asking the appropriate
questions, performing a careful physical examination, selectively obtaining
adjunct studies, and developing pattern recognition skills, the clinician can follow
the correct diagnostic path.

Suggested Readings and Key References
Bachur RG, Adams CM, Monuteaux MC. Evaluating the child with acute hip
pain (“irritable hip”) in a Lyme endemic region. J Pediatr 2015;166(2):407–
411.
Caird MS, Flynn JM, Leung YL, et al. Factors distinguishing septic arthritis from
transient synovitis of the hip in children. A prospective study. J Bone Joint