Perform a thorough physical exam and consider radiographs of both the area in question, as well as those areas proximal and distal.

Lower extremity pain may be a sign of significant pathology in children. In toddlers, it often presents as a limp or refusal to bear weight. Infants may present with discomfort during diaper changes or refusal to move one extremity. Localizing the pathology may be difficult because young children are often unable to communicate the site of pain. Also, disease in one area may present as referred pain to another area. This happens most commonly with the hip, which may present as referred pain to the thigh or knee. However, limp and referred pain may also be secondary to spinal pathology or gastrointestinal disease, such as appendicitis. The clinician may be misled if the entire lower extremity and the adjacent body parts are not evaluated.

The differential diagnosis of lower extremity pain, or limp, is broad and depends on the age of the child. Table 230.1 lists some of the common etiologies of lower extremity pain for different age groups. A selection of diagnoses that require urgent recognition, evaluation, and treatment will be reviewed here. A more expanded differential diagnosis can be found in the references provided or in separate chapters on developmental dysplasia of the hip and fracture patterns in nonaccidental trauma. Generally, specific causes of limp fall into one of three categories: pain, weakness, or structural abnormality. A thorough history, a meticulous exam, and the judicious use of lab studies and x-rays will usually lead to the correct diagnosis.

Legg-Calvé-Perthes disease (LCPD) and slipped capital femoral epiphysis are diseases of the hip, that if diagnosed early lead to improved outcomes. LCPD is a syndrome of avascular necrosis of the femoral head. Pain in LCPD is generally not severe and may be referred to the anteromedial thigh or knee. Some cases present with limp only. On exam, range of motion may be limited. Slipped capital femoral epiphysis occurs from acute or repetitive trauma to a presumably abnormal femoral growth plate. It occurs most commonly in the early teenage years, just prior to the adolescent growth spurt, and it is
associated with obesity. Along with external rotation of the affected limb, the presenting complaint is often limp with pain in the hip, thigh, or knee.