Blount disease is a growth problem that causes the bones of the lower leg to curve outward. In younger kids both legs are often affected, but in teens it's usually just one.
Blount disease is different from bowleggedness, which often affects babies and toddlers. Babies’ legs are naturally bowed at birth from being in the small space of the womb. The legs usually straighten out when babies start walking. But in a child with Blount disease, the curve only worsens without treatment. That's why early diagnosis is important.
Understanding Blount Disease
To understand Blount disease, it helps to know about the fibula and the tibia — the two bones that make up the lower leg. The fibula is the thinner bone on the outside of the leg (same side as the pinky toe). The larger bone, the tibia (or shinbone), is on the inside of the leg (same side as the big toe).
Kids and teens have a growth plate made of cartilage at the top of the tibia. The growth plate makes bone grow longer by making new bone material. Sometimes, though, when a lot of pressure is put on the growth plate, the bone might not grow normally. The inner part gets squeezed together and may even stop making new bone, while the outer part continues to grow normally. This uneven bone growth causes the tibia to bend outward instead of grow straight. (Need a visual? Take a coffee stirrer and hold it upright — now push down gently from the top. See the bend?)
Most kids who get Blount disease are overweight or obese or have rapidly gained weight. It’s also more common in girls, people of African heritage, kids who started walking at an early age, and those with a family member who had it.
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 pain that that gets worse.
A curved tibia also can cause other problems. For example, the feet can start to point inward instead of straight out (called in-toeing).
Blount disease can lead to arthritis of the knee joint and, in severe cases, trouble walking. Rarely, one leg may also become slightly shorter than the other.
If a doctor suspects Blount disease, he or she may refer your child to an orthopedic doctor (bone specialist) for leg X-rays and further examination.
Some mild bone changes can be difficult to spot in kids younger than 2, and it's often hard to tell whether a toddler has normal, age-appropriate bowing that will get better by itself or if it’s Blount disease. Usually by age 3 it's easier for a doctor to make a diagnosis.
Treatment of Blount disease depends on the child’s age and how curved the bone is. Kids younger than 2 might just need monitoring.
Kids between 2 and 4 years old and kids with severe bowing might require 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. Over time, the braces gradually shift leg bones to a straighter position.
For older kids and teens, or kids who don’t get better wearing KAFOs, other treatments are often necessary.
The surgeon can cut the bone, straighten it, and fasten it with plates and screws. Doctors call this 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 piece of equipment can be put on the outside of the leg. It holds the bones in place while gradually straightening the leg.
Whichever method the surgeon recommends, the procedure will be done under general anesthesia, which means your child will be sedated and asleep and won't feel a thing during surgery. Afterward, your child might need to wear a cast or use crutches for a while. Physical therapy also might be necessary.
Most kids who wear a brace or have a procedure for Blount disease get better and have active lives.
If being overweight was part of the cause of Blount disease, it's important for parents help their child 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 figuring out how to get your child on the road to a healthier lifestyle that includes a balanced diet and exercise, talk to your doctor.