Blount’s disease

Alternative names
Tibia vara

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

Causes, incidence, and risk factors

Blount’s disease occurs in young children and adolescents. The cause is unknown but is thought to be related to weight-related effects 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 correct 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.

The 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

• Sudden bowing of one or both legs
  
• May be rapidly progressive
  
• May appear asymmetric
  
• Primarily occurs 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).

Treatment

Mild deformity can be treated with a brace. Moderate to severe angulation may require surgery. Surgical treatment involves cutting the bone to straighten it and placing steel pins.

Expectations (prognosis)

Return to normal function and cosmetic appearance is expected after treatment.

Complications

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