With a prevalence as high as 15%, chronic pain is increasingly being recognized as a common problem in children and adolescents but one that remains poorly understood. This chapter describes evolving concepts of several syndromes in which musculoskeletal pain is a prominent feature. Interestingly, these pain syndromes frequently have overlapping features. However, most children can be readily diagnosed by the typical pattern of somatic complaints and the salient physical findings specific to each syndrome.
PATHOGENESIS AND EPIDEMIOLOGY
Growing pains are the most common cause of recurrent limb pain in children, and references to it can be found in the medical literature dating back more than 150 years. Growing pains occur in children between the ages of 3 and 12 and are characterized by intermittent nighttime nonarticular aching or pain most commonly in the legs. Recent prevalence estimates vary from less than 3% to as high as 36.9% in 4- to 6-year-olds in Australia. An extension of the syndrome in adolescents and adults may include restless legs syndrome. In a recent population study, the prevalence of restless legs syndrome was found to be 1.9% in 8- to 11-year-olds and 2% in 12- to 17-year-olds; a history of growing pains and sleep disturbances was more common in the study population. Interestingly, restless legs syndrome also is reported to be common in patients with fibromyalgia, another pain syndrome that is described later in this chapter. The pathogenesis of growing pains is unknown. Despite the name, it is almost certainly not due to growing. Perhaps this term is used because the condition occurs in children (who are always growing) and does not occur in adulthood (after cessation of growth). Theories have abounded about the etiology and have included overuse, anatomic abnormalities, perfusion problems, and emotional issues, but most have not been supported by subsequent research. Recently, investigators have shown that children with growing pains may have increased pain sensitivity and decreased bone strength as measured by quantitative ultrasound.
Growing pains typically are bilateral, usually occurring in the evening or at night, and not associated with limping or limited mobility. There is no history of trauma or infection, and objective findings are lacking on physical examination. The areas most frequently involved include the thighs, calves, and, occasionally, the forearms and trunk. In contrast to patients with juvenile idiopathic arthritis (JIA), who usually have more pain and stiffness when first arising in the morning, these children usually are asymptomatic in the morning.
Parents of children with growing pains report no swelling, color changes, or warmth of the affected limb. The physical examination is unrevealing. X-rays and laboratory tests may be necessary to alleviate parental concern, but if the clinical picture is typical, they are not necessary. If testing is done, it typically includes the erythrocyte sedimentation rate, complete blood count, and muscle enzyme ...