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Musculoskeletal complaints account for a significant number of outpatient visits to the pediatrician—up to 10% of non–well-child appointments in some studies. Only a minority of these visits result in hospitalization, but in many cases, even these admissions could have been avoided if a logical, stepwise approach to evaluation and management had been used. This chapter focuses on the entities to consider in a limping child and the appropriate approaches to take with regard to the history, physical examination, and diagnosis.
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The normal gait is the most efficient and stable means for humans to walk upright on two legs. For this gait to be altered, strong countervailing forces must be applied. These may be anatomic (e.g. broken bone, muscular weakness), neurologic (disrupted proprioception or balance), or nocioceptive in nature. Pain is the most common cause of an abnormal gait in children.
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Recognizing specific gait aberrations can facilitate the localization and identification of musculoskeletal pathology. For example, a psoas abscess is often difficult to diagnose because of poor localization of discomfort within the pelvis; pain may be perceived as occurring anywhere from knee to the diaphragm. Trying to walk with a psoas abscess, however, results in a characteristically altered gait, as contraction of the psoas muscle is avoided to minimize discomfort. This causes leaning to the involved side and using the bones of the pelvis and upper leg to substitute for the support usually provided by the psoas muscle. Further, the contralateral hemipelvis dips to keep the psoas muscle relaxed and thus avoid pain. The result is the Trendelenburg gait, which can be caused only by a pathologic condition involving the proximal femur or muscles of the pelvis (Figure 30-1). Analogous effects of other sites of pathology on gait are listed in Table 30-1.
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The key elements of the medical history that help identify the cause of a limp include the timing of the symptoms, the nature of the pain with regard to alleviating and exacerbating factors, particularly response to activity (Table 30-2), and the character of the pain, such as dull, sharp, radiating, or burning.
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