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Genu Varum (Bowlegs) and Genu Valgum (Knock-Knees)


Simeon A. Boyadjiev Boyd

, MD, University of California, Davis

Last full review/revision May 2020| Content last modified May 2020

The 2 major types of knee or femoral-tibial angular deformities are genu varum (bowlegs) and genu valgum (knock-knees). Untreated, both can cause osteoarthritis of the knee in adulthood.

(See also Introduction to Congenital Craniofacial and Musculoskeletal Disorders.)

Genu varum

Genu varum is common among toddlers and usually resolves spontaneously by age 18 months. If it persists or becomes more severe, Blount disease (tibia vara) should be suspected, and rickets and other metabolic bone diseases should also be ruled out.

Blount disease is due to a growth disturbance of the medial aspect of the proximal tibial growth plate; genu varum and tibial torsion may occur. Blount disease may occur in early childhood or in adolescence (when it is associated with overweight). Early diagnosis of Blount disease is difficult because x-rays may be normal; the classic x-ray finding is angulation (beaking) of the medial metaphysis. Early use of splints or braces can be effective, but surgery with or without an external fixator is often needed.

Genu valgum

Genu valgum is less common than genu varum and, even if severe, usually resolves spontaneously by age 9 years. Skeletal dysplasia or hypophosphatasia should be excluded. If marked deformity persists after age 10 years, surgical stapling of the medial distal femoral epiphysis is indicated.

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