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Joint complaints are common in children, and the presentation may vary depending on the underlying disease process and the age of the child. An infant may present with a red, swollen joint, decreased use of an extremity, or pain. In this age group, pain may be demonstrated by fussiness with manipulation, such as with diaper changes. A toddler or school-aged child may present with a complaint of pain, limp, or swelling noticed by a caregiver or with decreased use of an extremity. An adolescent is more likely to present with a complaint of pain, swelling, or stiffness. Joint complaints may be articular, originating directly from the joint, or nonarticular, arising from surrounding bone, muscles, soft tissue, or organs. This chapter focuses on articular pain while considering important differential diagnoses that may present with nonarticular or juxta-articular pain.
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Arthritis is defined as inflammation of a joint with two of the following: pain, swelling/effusion, limited range of motion, erythema, or warmth. Arthritis may affect a single joint (monoarticular) or multiple joints (oligoarticular if fewer than five joints; polyarticular if greater than or equal to five) and may be acute, chronic (lasting ≥6 weeks), or acute on chronic. Arthralgia is joint pain without other signs of inflammation. Enthesitis is tenderness due to inflammation of the tendon insertion into bone.
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DIFFERENTIAL DIAGNOSIS
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The causes of joint pain may be classified as infectious, postinfectious, rheumatologic, autoinflammatory, hematologic, oncologic, mechanical/traumatic, and other (including genetic and metabolic) (Table 15-1). In this chapter, we will discuss disease diagnosis but not address treatment options.
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