What Is Blount's Disease?

Medically Reviewed by Poonam Sachdev on April 28, 2022

Blount's disease affects the growth of the bones near the knee. Your child may appear bow-legged and complain of knee pain. The teen leg disease is different from the disease in childhood. Blount's disease looks similar to the common bow legs of childhood, but the knee defects can be severe and permanent. Recognizing Blount's disease early and starting treatment soon gives better outcomes.

What Is Blount's Disease?

The bones at the knees have two growth plates. The medial plate lies on the inner side of the limb. The lateral plate lies on the outer side. Blount's disease causes the growth of the medial plate to slow down or stop. The lateral (outer) plate continues growing, bending the bone. The disorder has two forms — infantile and adolescent. 

Infantile Blount's disease. This form happens in children. Children often have bowlegs up to the age of 2 years. Instead of getting better, it gets worse when your child has infantile Blount's disease. This form of the disease affects only the tibia (the shin bone). It is more common than the teen leg disease and affects both sides. Infantile Blount's disease can resolve on its own, may respond to non-surgical treatment, or may progress continuously. 

The cutoff for infantile (also called early-onset) Blount's disease is 10 years. It is most commonly seen around 3 years. The knee deformity and other problems of the lower limbs will increase without treatment. The child may not be able to walk.

If not treated on time, the growth plate fuses and stops growing. This is called epiphysiodesis, and it cannot be reversed. The final length of the limb will be reduced.

Some children with early-onset Blount's disease may recover without active treatment. The main risk for the disease getting worse is overweight and obesity. Blount's disease progresses in most children, with worsening alignment of the bones.

Adolescent Blount's disease. This happens in children over 10 and teens. It is more likely to affect one side. It involves both the tibia (the leg bone) and the femur (the thigh bone). 

Blount's disease can have effects apart from the bowleg look. The bad alignment of the joint can cause abnormal wear and tear on one side. Osteoarthritis can happen early. One leg may become shorter than the other. 

Blount's Disease Causes

The cause of Blount's disease is not definitely known. A few things are associated with it: 

  • It runs in families. There may be a genetic cause.
  • Early walkers (before 12 months) are more likely to have it.
  • It is more common in overweight children. The compressive forces of overweight on the growth plate may be responsible. 

Blount's Disease Symptoms

Genu varum is the scientific name for bow legs and is the chief symptom. You will notice your child has bow legs. Blount's disease in children is usually not painful. 

Teenagers usually have significant pain and take over-the-counter pain medicine for it. They also feel that the knee may give way. Sometimes, the leg bone is twisted inwards, leading to in-toeing. 

Blount Disease Diagnosis

If you feel your child or teen is not walking normally, you should talk to your pediatrician. They may ask you to consult an orthopedic surgeon, a doctor specializing in bone and joint disorders. They may ask for X-rays of the knee joint, which will help them diagnose Blount's disease. 

Magnetic resonance imaging (MRI) provides more detailed information. Your physician can see the structure of the knee joints and the bones' growth plates and their blood supply. This helps decide the stage of the disease and the treatment plan.

Other conditions also cause a bowleg deformity. Your physician will consider these before starting treatment: 

  • Normal bow-leggedness of childhood. It can persist for a year after your child learns to walk.
  • Infection or injury to the joint. Some deformities may remain for a long time.
  • Congenital deformities. The bones may be structured differently at birth. 
  • Metabolic diseases. Some disorders weaken the bones and change their structure.
  • Fibrous dysplasia. A condition in which bone is replaced by fibrous tissue with poor strength and rigidity.

Blount's Disease Treatment

If your child has Blount's disease, there are three options for treatment. 

Observation. Your orthopedic surgeon will measure the legs and the deformity of your child's legs. They will also take X-rays from different angles to assess the problem. If they feel the bowing is mild, they may advise you to observe and wait. You will need to return to the orthopedic surgeon from time to time. They will monitor the progress of the disease. Often, the bowing will correct itself over the next year.

Most children with infantile (early-onset) Blount's disease have progression. The disease gets worse over time. When observation is chosen as the treatment, frequent and careful monitoring is crucial.

Non-surgical treatment. This uses braces worn by your child to straighten the knees slowly. As the bones grow, the braces guide them into a straighter position. Your doctor will monitor the effect of the treatment. If your child's leg is not straight by age 4 years, they may advise surgical correction. 

The braces are known as KAFO (knee ankle foot orthotic) braces. They attach to your child's lower limb from the top of the thigh to the tips of the toes. Your child must wear the braces for several hours each day. Your doctor will judge effectiveness after a year of use. 

The braces themselves are difficult to use on children so young. Surgery is usually needed.

Surgical treatment. Many types of surgical procedures are used to treat Blount's disease. An osteotomy cuts a part of the bone and straightens the bone. You will see the benefit immediately. 

Another type of treatment puts staples or plates on one side of the bone to prevent growth on that side. The other side continues growing, and the bone becomes straight. This type of treatment is called guided growth treatment.

For adolescents, surgery is often the best treatment. A wedge-shaped piece of the bone is removed (an osteotomy). This aligns the leg correctly and straightens it. Your doctor will fix a plate at the operation site. This plate may need to be removed after one or two years.

Maintaining a healthy weight helps in the treatment.  

Blount's disease treatment can be challenging. Using braces for some months or years needs determination. You may need to take your child or teen to your physician several times for assessment and treatment. They may also need surgery. 

Most children and teens who have had proper treatment walk normally and participate in competitive sports. Paying attention to teen leg problems early is vital. Early detection and expert treatment lead to good outcomes. 

Show Sources

Columbia University Irving Medical Center: "Blount's Disease (Pediatric)."
Hospital for Special Surgery: "Blount's Disease: An Overview."
Johns Hopkins Medicine: "Blount's Disease."
Nemours Children's Hospital: "Blount Disease."
Orthopaedics & Traumatology: Surgery & Research: "Blount disease."

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