Blount's Disease

Definition

Blount's disease is a growth disorder of the tibia (shin bone) that causes the lower leg to angle inward, resembling a bowleg.

Alternative Names

Tibia vara

Causes, incidence, and risk factors

Blount's disease occurs in young children and adolescents. The cause is unknown but is thought to be due to the effects of weight on the growth plate. The inner part of the tibia, just below the knee, fails to develop normally, causing angulation of the bone.

Unlike bowlegs, which tend to straighten as the child develops, Blount's disease is progressive and the condition worsens. It can cause severe bowing of the legs and can affect one or both legs.

This condition is more common among African-American children. It is also associated with obesity and early walking. There does not appear to be an obvious genetic factor.

Symptoms

• Bowing of one or both legs that may:
  • Be rapidly progressive
  • Appear asymmetric
  • Primarily occur just below the knee

Signs and tests

Physical examination shows that the lower legs angle inward. An x-ray of the knee and the lower leg confirms the diagnosis (see joints x-ray).

Expectations (prognosis)

Return to normal function and cosmetic appearance is expected if the knee can be properly aligned.

Complications

Failure to treat Blount's disease may lead to progressive deformity.

Blount's disease may come back after surgery, especially in younger children.

Because of the bowing, a leg-length discrepancy may result. This may result in disability if the discrepancy is significant (greater than 1 inch) and is not treated.

Calling your health care provider

Call for an appointment with your child's health care provider if your child's leg or legs appear to be bowing. Also call for an appointment if your child has bowed legs that appear to be getting worse.

Prevention

Weight loss for overweight children may be helpful.

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Bowlegs