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.