What Is Blount Disease?
Blount disease is a growth disorder that affects the bones of the lower leg, causing
them to bow outward. It can affect people at any time during the growing process,
but it's more common in kids younger than 4 and in teens.
In Blount disease, a lot of pressure is put on the growth plate
at the top of the tibia. This is called the physis and it's made
out of cartilage, which is weaker than bone. The job of the physis
is to allow the bone to lengthen and grow.
But this excess pressure prevents the bone from growing normally. Instead, 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.
Blount disease is very different from the bowlegs that babies and toddlers have.
Their legs are naturally bowed and usually straighten out when they start walking.
But with Blount disease — whether it starts in early childhood or the teen
years — the curve gets worse if it's not treated. So early diagnosis is very
important.
What Are the Symptoms?
The most obvious sign a person might have Blount disease is bowing of the leg below
the knee. In young kids this is usually not painful, but for teens it can be (it may
feel like a growing pain in the knee area). The pain may come and go. Most teens have
already been taking over-the-counter pain relievers for it by the time they see a
doctor.
It can cause other problems, too, mainly due to the way the lower leg bears the
weight of the body. 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 (usually decades), Blount disease can lead to arthritis of the knee joint
and trouble walking. One leg may also become slightly shorter than the other.
What Causes Blount Disease?
Most people 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.
How Is It Diagnosed?
If your legs start bowing — especially if you also have knee pain that seems
to be getting worse and can't be traced to an injury — your doctor may consider
Blount disease as a possibility. If so, your doc will refer you to an orthopedic specialist
(a doctor who treats bone problems).
The orthopedic doctor will do a complete physical exam and also take X-rays of
your legs. These let the doc look for the abnormal bone growth patterns at the top
of the tibia that are the telltale sign of Blount disease. They also help the doctor
measure how severe the bowing is.
How Is it Treated?
How doctors treat Blount disease depends on how old the person is and how far the
disease has progressed. Young kids may simply need to wear leg braces. Most older
kids and teens will need surgery.
Many different types of surgeries can correct Blount disease — some involve
cutting the tibia, realigning it, and holding it in place with a plate and screws
(this is called an osteotomy); some involve removing the damaged
growth plate; and some use a device called an external fixator to
hold the bones in place from the outside. If a person's toes turn in, surgeons may
correct the twist that's causing that, too.
If surgery is necessary, it will be done under general anesthesia
(you will be completely asleep and not feel anything). Afterward, you might wear a
cast and use crutches for a while. You'll also probably need physical
therapy. The good news is that most teens make a complete recovery.
The Outlook
Most teens who have surgery to correct Blount disease can return to all their normal
activities, even competitive sports.
One lesson many people take away from dealing with Blount disease is the importance
of getting to a healthy weight. Staying
at a healthy weight can help protect bones and joints from excess wear and tear
that can damage them over time.
If you'd like help figuring out how to start on a safe diet and exercise plan,
talk to your doctor.
Date reviewed: January 2017
