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Approach to the child with bow-legs

Scott B Rosenfeld, MD
Section Editors
William Phillips, MD
Jan E Drutz, MD
Deputy Editor
Mary M Torchia, MD


Bow-legs (genu varum) is an angular deformity at the knee where the apex of the deformity points away from the midline (figure 1). Knock-knees (genu valgum) are an angular deformity at the knee where the apex of the deformity points toward the midline (figure 1).

Bow-legs and knock-knees are among the most common musculoskeletal anatomic variations encountered by pediatric primary care providers and a common reason for referral to a pediatric orthopedic surgeon. However, most children with bow-legs or knock-knees have variations of normal lower-extremity development that can be monitored by the primary care provider.

An understanding of the normal physiologic development of the lower extremity is essential in differentiating physiologic from pathologic alignment. Pathologic causes of bow-legs include Blount disease, nutritional rickets and other metabolic bone diseases, skeletal dysplasia, infection, trauma, and neoplasia. Unlike physiologic bowing, these conditions generally do not improve over time and may require treatment with bracing or surgery.

This topic will provide an overview of normal physiologic alignment of the lower extremity, physiologic and pathologic causes of bowing, and an approach to the child with bow-legs. Knock-knees are discussed separately. (See "Approach to the child with knock-knees".)


An understanding of normal physiologic development of the lower extremity is essential to differentiation of physiologic from pathologic deformities. Lower-extremity alignment goes through a predictable progression from varus (bow-legs), to neutral, to valgus (knock-knees), and back towards neutral over the first seven years of life (figure 2 and figure 3) [1]. Final adult lower-extremity alignment is slightly valgus. There is a wide range of normal values [1,2].

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Literature review current through: Nov 2017. | This topic last updated: Jun 06, 2017.
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