Genu varum (bowed legs) is an angular deformity at the knee with the tibia adducted (varus) in relation to the femur. Genu valgum (knock-knees) is characterized by alignment of the knee with the tibia abducted (valgus) in relation to the femur.

Genu varum (bowed legs), when extreme or unilateral, may result from a variety of underlying conditions: rickets, dyschondroplasia, osteogenesis imperfecta, osteochondritis, Blount disease (tibia vara), or injury to the medial proximal epiphysis of the tibia. Extreme degrees of physiologic bowing of the legs may occur in the young child and resolve over time without treatment (Figure 183-11).

Genu valgum (knock-knees) is often associated with pronation and is more apt to be marked in the child who is overweight. The degrees of knock-knee can be gauged by measuring the distance between the medial malleoli when the child is standing with the knees approximated (Figure 183-12). Injury to the lateral proximal tibial epiphysis can cause unilateral genu valgum (Figure 183-13). As with extreme bowing, underlying generalized diseases of the bone can cause marked bilateral genu valgum.

Figure 183-11 A, Extreme physiological bowing of the legs at age 18 months. B, Spontaneous resolution over time (age 7 years). (Sharrard WJW. Paediatric Orthopaedics and Fractures. Oxford, NY: Blackwell Scientific; 1971. Reprinted by permission of Blackwell Publishing Ltd.)

Figure 183-12 Marked degree of physiological genu valgum. At age 11 years the distance between the medial malleoli measured 4 inches. (Sharrard WJW. Paediatric Orthopaedics and Fractures. 2nd ed. Oxford, NY: Blackwell Scientific; 1979. Reprinted by permission of Blackwell Publishing Ltd.)

Figure 183-13 Unilateral genu valgum caused by previous injury to the lateral aspect of the right proximal tibial epiphysis. (Sharrard WJW. Paediatric Orthopaedics and Fractures. 2nd ed. Oxford, NY: Blackwell Scientific; 1979. Reprinted by permission of Blackwell Publishing Ltd.)

A history of uterine crowding during fetal development can be associated with extreme cases of genu varum or genu valgum. Prior trauma or a variety of endocrine, metabolic, or bone abnormalities may result in pathological degrees of bowing or knock-knees.

From birth until 18 months of age, a distinct physiological bowing of the lower extremities of 10 to 15 degrees is normal. Bowing is followed by a transitional period over the next year or so, during which continued growth results in a knock-knee pattern of 10 to 15 degrees, which assumes prominence by age 3 to 4 years. Knock-knee persists until later childhood or early adolescence when a balancing and straightening occur spontaneously. Physicians must be aware of this normal developmental pattern to avoid unnecessary treatment of mild to moderate degrees of bowed legs and knock-knees. However, marked degrees of these conditions require investigation to rule out underlying disease that can result in permanent deformity.

Genu varum (bowed legs), when extreme or unilateral, requires radiographic examination to exclude rickets, dyschondroplasia, osteogenesis imperfecta, osteochondritis, Blount disease (tibia vara), or injury to the medial proximal epiphysis of the tibia.

Simple observation and reassurance are all that are required for physiological genu varum and genu valgum, given that these conditions spontaneously correct 99% of the time. When identified, underlying etiologies of extreme varus or valgum deformities must be effectively treated to improve angulation. Treatment of severe bowing or knocking of the knees caused by underlying disease is determined by the nature of the condition and may include wedge osteotomy or epiphyseal stapling.