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Blount Disease

Blount disease is a growth disorder that affects the bones of the lower leg, causing them to bow outward. In younger kids, just the tibia (shin bone) is affected. In teens, it's usually both the tibia and the femur (thigh bone).

Many babies are born with slightly bowed legs from being in the small space of the womb. Their legs usually straighten out as they grow and start walking.

Blount disease is different. The curve gets worse if it's not treated, so early diagnosis is very important.

Risks Factors

Most kids who get Blount disease are overweight or gained weight very quickly. It's also more common in people of African heritage, kids who started walking at an early age, and those with a family member who had it.

In Blount disease, a lot of pressure is put on the growth plate (an area of growing bone tissue) at the top of the tibia. As a result, the bone can't grow normally. The lateral (outer) side of the tibia keeps growing but the medial (inner) side of the bone does not. 

This uneven bone growth causes the tibia to bend outward instead of grow straight. One leg may also become slightly shorter than the other.

Signs and Symptoms

The most obvious symptom of Blount disease is a bowing of the leg below the knee. In young kids, it's usually not painful, though it can affect the way they walk. For preteens and teens, Blount disease may cause knee pain that gets worse with activity.

The tibia can be rotated as well as bowed, causing a condition called in-toeing (when the feet point inward instead of straight out).

Over time, Blount disease can lead to arthritis of the knee joint and, in severe cases, trouble walking.

Diagnosis

When doctors suspect Blount disease, they may recommend taking a child to an orthopedic doctor (bone specialist) for leg X-rays and further examination.

Mild bone changes can be hard to spot in kids younger than 2 because their bowed legs might be normal and straighten out on their own. It's easier for doctors to diagnose Blount disease in kids after age 2.

Treatment

Treatment of Blount disease depends on a child's age and how curved the bone is.

Usually, doctors will just keep a close eye on the condition in children younger than 2. Kids 2 to 4 years old and those with severe bowing might need leg braces, called KAFOs (knee-ankle-foot orthotics). KAFOs, which go from the thigh to the toes, are created for kids using a mold of their leg. The hope is that the braces gradually shift leg bones to a straighter position over time. However, doctors have differing opinions on KAFOs. If you have questions about them, talk to your doctor.

Older kids and teens, or kids who don't get better wearing KAFOs, might need surgery:

  • The surgeon can cut the bone, straighten it, and fasten it with plates and screws. This is called an osteotomy.
  • Another procedure can slow or stop the growth of half of the growth plate to allow the other side to catch up and straighten the leg.
  • A device called an external fixator can be put on the outside of the leg and attached to the bones after they are cut. It holds the bones in place while gradually straightening the leg.

If surgery is necessary, it will be done under general anesthesia. This means your child will be sedated and asleep and won't feel anything. Afterward, your child might wear a cast or use crutches and a wheelchair for a while. Physical therapy also might be needed.

Outlook

Most kids who are treated for Blount disease get better and have active lives.

If being overweight caused the Blount disease, it's important for parents to help their child reach and maintain a healthy weight. This can reduce stress on the bones and joints and prevent other long-term problems from weight gain (like type 2 diabetes and heart disease).

If you need help getting your child to adopt a healthier lifestyle that includes a balanced diet and exercise, talk to your doctor.

Reviewed by: Kevin M. Neal, MD
Date reviewed: September 05, 2017