Adults typically have osteomalacia and may develop bone pain, joint stiffness, and overgrowth of bone at the site of muscle attachments (enthesopathy). Growth delay is often present within the first few months of life, but the lower extremity bowing may not develop until the child commences weight bearing.
Sillence, in Emery and Rimoin's Principles and Practice of Medical Genetics (Sixth Edition), 2013 157.13.1 Clinical FindingsĬhildren with XLH exhibit short stature, rickets, lower extremity deformity (genu varum or valgum), and dental abscesses. Patients with idiopathic genu valgum may show flattening of the lateral femoral condyle. Specific causes of pathologic valgum should be evaluated, such as angular deformity from prior fracture or physeal injury. 62 The tibiofemoral angle is measured as the angle formed by lines drawn along the long axes of the femoral and tibial shafts. 63 A lateral radiograph may be helpful to detect abnormalities in the sagittal plane if such deformity is suspected. 62, 63 The image is taken with the knees facing forward, disregarding the positioning of the feet in order to get a true understanding of the mechanical axes. Osteoarticular ImagingĪ single long-cassette anteroposterior radiograph during weight bearing is obtained of both lower extremities, including the hips, knees, and ankles. 62 However, radiographs have been recommended in cases of suspected pathologic genu valgum for example, when deformity is severe or asymmetric, there are other musculoskeletal abnormalities, there is a positive family history, the tibiofemoral angle is greater than 15 to 20 degrees, or the patient is of short stature 62, 63 ( Figure 25-15). In patients with clinical findings compatible with physiologic genu valgum, radiographs are typically not necessary. 65, 66 A medial thrust is seen in pathologic but not physiologic states. 64 Clinical assessment should include observation of gait, particularly the stance phase in order to detect presence of a medial thrust at the knee, the presence of which indicates that the medial ligamentous and muscular knee restraints have become insufficient to resist deformity just after heel strike. 62 Assessment of genu valgum on clinical exam includes measurement of the tibiofemoral angle and intermalleolar and intercondylar distances, for which tables of normal ranges have been reported. The child with physiologic valgus will typically be less than 7 years of age, be of normal stature, will have symmetric involvement of the lower limbs, and will have a tibiofemoral angle of under 15 degrees. Unilateral valgus deformity requires investigation for an underlying cause. 62, 64 Several graphs of normal values have been published. 63 By definition, pathologic genu valgum exists when the tibiofemoral angle is more than two standard deviations above normal. Minimal change in valgus is normally observed during adolescence. 62 Then gradual reduction of valgus alignment to the normal “adult” level of 5 to 7 degrees occurs by 6 to 7 years of age. 62 It is important to understand the normal developmental sequence, which begins with maximal bowing (genu varum) in the newborn period, straightening between 20 and 22 months of age, and then reversal of this configuration into maximum valgus angulation of 10 to 15 degrees at approximately 3 years of age. 62 Less commonly, focal or systemic pathologic conditions are the culprit, resulting in valgus that is more inclined to progress and require treatment. The overwhelming majority of cases are physiologic variants that will resolve.
Genu valgum is a common entity that is most often physiologic in nature and part of the normal developmental change in lower extremity alignment that occurs during childhood.
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