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.