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In a child with a limp that occurs after trauma, localized radiographs or radiographs of the tibia on the affected side are most likely to reveal the diagnosis.
Suspect hip pathology in a child with a limp and knee or thigh pain.
Septic arthritis should be suspected in a child with fever, painful limp, elevated C-reactive protein (CRP) >2 mg/dL or erythrocyte sedimentation rate (ESR) >40, and a white cell count >12 × 109/L.
In a child presenting with a limp and without a history of trauma, fever or systemic symptoms, commence imaging with a hip ultrasound followed by radiographs if the ultrasound is negative.
An MRI should be performed early in the diagnostic process if infection is a possible cause for a limp in a child.
A history of trauma and the presence of fever are important symptoms to consider when ordering an expanded diagnostic workup for a limp.
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A limp is a jerky, uneven, or laborious gait, usually caused by pain, weakness, or deformity The development of a child's gait is important to identifying the etiology of a limp. Children begin to crawl at 9 months, independently walk at 12 to 15 months and run at 18 months. At 1 year of age, the normal infant has a broad-based gait and moves the limbs rapidly with short steps with the arms flexed and without reciprocal arm movement. The foot makes contact with the ground all at once. By 3 years most adult kinematic patterns are developed. With subsequent changes in velocity and step length an adult gait pattern is achieved at 7 years. The adult gait consists of a stance phase and a swing phase. The stance phase (60% of the gait cycle) begins when the heel of one foot strikes the ground and bears all the weight, advances to a foot flat position during midstance and progresses to push-off by the toes as weight gets transferred from the heel to the forefoot. The swing phase begins when the opposite foot pushes off the ground; the leg is swung forward with the foot clearing the ground until the heel makes contact with the ground. The most common cause for a limp is trauma; Table 108-1 lists other causes. The differential diagnosis is influenced by the duration and type of limp, age of the child, and the anatomic site affected.
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