Blount Disease in Children: When Are Bowed Legs a Warning Sign?

Have you noticed that your child’s legs curve outward, creating a noticeable gap between the knees when standing with the ankles together, or that the bowing seems to worsen as your child grows? This could indicate Blount disease in children.

Bowed legs are common in babies and toddlers.

In many children, the legs gradually straighten as they grow without requiring treatment.

However, when the bowing becomes more noticeable, affects one leg more than the other, or does not improve with age, it may indicate an underlying bone-growth problem.

One condition that can cause progressive bowing is Blount disease, also known as tibia vara.

It affects the growth plate near the upper part of the shinbone and can gradually change the alignment of the lower leg.

Recognizing the difference between normal developmental bowing and Blount disease is important.

Early assessment helps identify children who may need orthopedic treatment while their bones are still growing.

What Is Blount Disease?

Blount disease is a growth disorder affecting the upper part of the tibia, or shinbone, near the knee.

The growth plate on the inner side of the upper tibia does not develop normally.

As a result, the inner portion of the bone grows more slowly than the outer portion.

This uneven growth causes the lower leg to angle outward, creating a bowed appearance.

The medical term for this alignment is genu varum.

Blount disease can affect one or both legs.

Depending on its severity, children may also develop:

• Inward twisting of the shinbone.
• Changes in their walking pattern.
• Uneven weight distribution between the legs.
• A difference in leg length.
• Knee discomfort, particularly in older children.

Unlike normal developmental bowing, Blount disease can become progressively more pronounced without appropriate management.

What Causes Blount Disease in Children?

The exact cause of Blount disease is not fully understood.

Researchers believe that abnormal mechanical loading around the developing upper tibial growth plate may contribute to the condition.

Several factors are associated with an increased likelihood of developing Blount disease.

1. Higher Body Weight

Higher body weight increases the load placed on the developing knee and shinbone.

This is an important associated risk factor, particularly in adolescent Blount disease.

However, children at a healthy weight can also develop the condition.

2. Early Independent Walking

Some studies have identified early independent walking, particularly before 12 months, as an associated factor in infantile Blount disease.

However, walking early does not mean a child will develop Blount disease.

It should not be treated as a cause on its own.

3. Family History

A family history of Blount disease may increase susceptibility.

Genetic and environmental factors may both contribute, although the condition is not usually explained by a single inherited gene.

4. Abnormal Mechanical Stress During Growth

The growth plate is responsible for the normal development of a child’s bones.

In susceptible children, repeated or uneven loading may contribute to abnormal growth on the inner side of the upper tibia.

The relationship between these factors is complex, and researchers have not established one single cause.

What Are the Types of Blount Disease?

Blount disease is generally classified into two forms according to the age at which it develops.

Infantile Blount Disease

Infantile Blount disease usually develops before four years of age.

It may become noticeable when a toddler’s legs do not straighten as expected during early childhood.

Common features include:

• Bowing of both legs, sometimes with different severity.
• More noticeable curvature around the upper shinbone.
• One leg appearing more bowed than the other.
• Inward rotation of the lower leg.
• Gradual worsening of the deformity.

Early infantile Blount disease can sometimes be difficult to distinguish from normal developmental bowing.

This is why clinical follow-up is important when the appearance of the legs is concerning.

Adolescent Blount Disease

Adolescent Blount disease generally develops after ten years of age.

It is more frequently associated with higher body weight and may affect only one leg.

Older children and teenagers may experience:

• Bowing around the knee and upper shinbone.
• Pain along the inner side of the knee.
• Changes in walking pattern.
• Difficulty with running or sports.
• Uneven leg alignment or leg length.

The distinction matters because treatment depends on the child’s age, severity of the deformity and remaining growth potential (Pediatric Orthopaedic Society of North America)

Normal Bowed Legs vs Blount Disease: How Can Parents Tell the Difference?

Not every child with bowed legs has a bone-growth disorder.

Physiological genu varum, the medical term for normal developmental bowing, is common in babies and toddlers.

It usually begins to improve around 18 months and generally corrects by three to four years of age.

Blount disease follows a different pattern. Instead of gradually improving, the bowing may persist or become more pronounced.

Feature	Normal developmental bowing	Blount disease
Typical age	Babies and young toddlers	Infantile or adolescent onset
Appearance	Usually symmetrical	May be asymmetrical
Progression	Gradually improves	May persist or worsen
Location	General curvature of the legs	Often more pronounced near the upper tibia
Pain	Usually painless	Often painless in young children; pain may occur in adolescents
Management	Usually observation	May require bracing or surgery

In children younger than two years, it can sometimes be difficult to distinguish early Blount disease from physiological bowing.

A doctor considers the child’s age, growth pattern, leg alignment and changes over time rather than relying on appearance alone. (AAOS)

What Are the Early Signs of Blount Disease?

The most noticeable sign is usually a change in the shape of one or both lower legs.

Parents may notice the following changes.

1. Increasing Bowing of the Legs

The legs may appear increasingly curved when the child stands with the feet together.

The gap between the knees may become more noticeable rather than gradually reducing with growth.

2. Unequal Leg Alignment

One leg may look more bowed than the other.

Although normal developmental bowing is usually symmetrical, Blount disease can produce unequal deformity.

3. Changes in Walking Pattern

Some children develop an unusual walking pattern as the deformity progresses.

The knee may move outward during the weight-bearing phase of walking, creating a noticeable sideways movement.

4. Inward Twisting of the Lower Leg

The shinbone may rotate inward, sometimes making the feet point towards each other while walking.

This can affect the child’s overall lower-limb alignment.

5. Knee Discomfort in Older Children

Young children with infantile Blount disease often have little or no pain.

Adolescents may experience discomfort around the inner knee, particularly during walking, running or sports.

6. Difference in Leg Length

In more advanced cases, uneven growth can contribute to a difference in leg length.

Parents should arrange an assessment if the bowing is worsening, particularly after the age of two to three years, or if one leg is noticeably more affected.

Can Blount Disease Affect a Child’s Walking and Physical Development?

Yes.

As the deformity progresses, changes in the alignment of the tibia can affect how a child stands, walks and distributes body weight.

Possible functional difficulties include:

• Uneven weight-bearing between the legs.
• Changes in walking pattern.
• Difficulty running or participating in sports.
• Reduced confidence during physical activities.
• Knee discomfort during prolonged activity.
• Difficulty with some weight-bearing movements.

Some children may continue walking and playing without obvious difficulty, particularly during the early stages.

However, the absence of pain does not rule out Blount disease.

Changes in leg alignment and walking pattern can be important signs even when a child does not complain of discomfort.

How Is Blount Disease Diagnosed?

Diagnosis involves a clinical examination and imaging when indicated.

1. Physical Examination

The doctor may assess:

• The shape and alignment of both legs.
• Whether the bowing is symmetrical.
• The child’s height and weight growth patterns.
• Knee and ankle alignment.
• Foot position and inward rotation of the shinbone.
• Walking pattern and stability.
• Whether the child experiences pain or difficulty with movement.

The doctor may also examine the hips and feet to identify other conditions that could contribute to the appearance of bowed legs.

2. X-rays

Standing X-rays of the lower limbs help doctors examine the alignment of the bones.

They can identify changes around the upper tibial growth plate, including irregular growth and characteristic changes in the shape of the bone.

Doctors may use measurements such as the metaphyseal-diaphyseal angle, also known as the Drennan angle, to help distinguish physiological bowing from Blount disease.

However, this measurement should not be interpreted in isolation. The child’s age, clinical examination and other X-ray findings also matter.

3. Additional Investigations

MRI may be considered in selected cases when more detailed information about the growth plate or joint surface is needed.

If the doctor suspects another condition, such as nutritional rickets, blood tests may also be recommended.

The purpose of these investigations is to confirm the cause of the bowing and guide appropriate treatment.

How Is Blount Disease Treated?

Treatment depends on the child’s age, severity of bowing, stage of the condition and remaining growth potential.

The main aims are to improve leg alignment, protect the knee joint and reduce the risk of progressive deformity.

1. Observation and Regular Monitoring

Some children with mild or uncertain early changes may need regular clinical and X-ray monitoring.

This helps the orthopedic specialist determine whether the bowing is improving, remaining stable or progressing.

Observation should be guided by a clinician rather than relying on appearance alone.

2. Bracing

Younger children with selected early-stage infantile Blount disease may benefit from a specialized knee-ankle-foot orthosis (KAFO).

The brace is designed to support the leg and apply corrective forces while the bones are growing.

Bracing is not suitable for every child. Its effectiveness depends on age, severity of the deformity and the stage of growth-plate changes.

It is generally less effective in older children and adolescents.

3. Surgery

Surgery may be recommended when the deformity is severe, continues to progress or is unlikely to respond to bracing.

Depending on the child’s growth and bone alignment, surgical options may include:

• Corrective osteotomy: The surgeon cuts and repositions the tibia to improve alignment.
• Guided growth: A small implant temporarily slows growth on one side of the growth plate, allowing the other side to catch up.
• Gradual correction: An external fixation device may be used in selected complex deformities to correct alignment progressively.

The orthopedic surgeon selects the procedure according to the child’s individual condition. (Pediatric Orthopedic Society of North America, Blount Disease)

What Is the Role of Pediatric Physiotherapy in Blount Disease?

Paediatric physiotherapy can support a child’s movement, strength and functional recovery.

However, it is important to understand that physiotherapy exercises cannot independently correct the abnormal growth of the tibial growth plate.

The main role of physiotherapy is to assess movement difficulties, maintain functional abilities and support rehabilitation after orthopedic treatment, particularly following surgery.

1. Assessment of Walking and Lower-Limb Movement

A pediatric physiotherapist may assess:

• Walking pattern and weight distribution.
• Balance and postural control.
• Hip, knee and ankle movement.
• Lower-limb muscle strength.
• Functional movements such as standing, walking and climbing stairs.
• The child’s ability to participate in age-appropriate activities.

This assessment helps identify movement limitations and establish appropriate rehabilitation goals.

2. Strengthening Exercises

After medical clearance, strengthening exercises may help improve lower-limb and trunk muscle function.

Depending on the child’s needs, activities may include:

• Sit-to-stand practice.
• Supported squats.
• Step-ups and step-downs.
• Age-appropriate balance activities.
• Progressive walking exercises.

Exercises should be selected according to the child’s treatment stage, pain levels and orthopedic instructions.

3. Balance and Coordination Training

Changes in leg alignment can affect how a child distributes weight while standing and walking.

Physiotherapy may include supervised balance activities, controlled weight shifting and functional movement practice to improve stability.

4. Gait Rehabilitation After Surgery

Following surgical correction, some children need support to return to their usual walking pattern.

Rehabilitation may gradually progress through:

• Safe standing and weight-bearing as permitted.
• Walking with prescribed support or walking aids.
• Improving knee and ankle movement.
• Progressive strengthening.
• Stair climbing and age-appropriate activities.

The timing of each stage depends on the surgical procedure, bone healing and the orthopedic surgeon’s weight-bearing instructions.

5. Parent Education and Home Rehabilitation

Parents play an important role in supporting recovery.

A physiotherapist may explain:

• How to help the child move safely at home.
• Which activities are appropriate during recovery.
• How to use prescribed walking aids.
• Which movements or activities should temporarily be avoided.
• How to follow the home exercise program.
• When to report pain, swelling or changes in walking.

A home program should be individualized rather than based on a generic set of exercises.

Can Blount Disease Be Prevented?

There is no guaranteed way to prevent Blount disease because its exact cause is not fully understood.

However, supporting healthy growth and development is important.

Parents can:

• Encourage balanced nutrition to support bone health.
• Attend routine growth and developmental check-ups.
• Discuss concerns about persistent or worsening bowing with a pediatrician.
• Support healthy, enjoyable physical activity appropriate for the child’s age.
• Seek advice if the child develops significant changes in walking or leg alignment.

Avoid using corrective shoes, braces or exercises without professional advice.

These do not reliably correct Blount disease and may delay appropriate assessment.

What Is the Long-Term Outlook for Children With Blount Disease?

The long-term outlook depends on the child’s age when the condition is identified, the severity of the deformity and the treatment provided.

Children diagnosed early may have more treatment options because their bones have more remaining growth potential.

Some children respond to bracing, while others require surgical correction. More advanced deformities may need complex procedures and longer follow-up.

Regular orthopedic monitoring is important because deformity can recur during growth in some children.

Physiotherapy can help children regain strength, mobility and confidence after treatment, but long-term outcomes also depend on successful correction and continued monitoring of bone alignment.

When Should Parents Seek Medical Assessment?

Arrange an assessment if your child has:

• Bowed legs that are becoming more pronounced.
• One leg that looks more curved than the other.
• Persistent bowing after the age of three years.
• A noticeable change in walking pattern.
• Knees that move sideways during walking.
• Knee pain, particularly during activity.
• A visible difference in leg length.
• Difficulty walking or participating in normal activities.

A child with severe pain, sudden inability to bear weight or a new deformity after an injury needs prompt medical assessment.

Fever with a hot, swollen or painful joint also requires urgent evaluation.

Early assessment is particularly important because some treatment options depend on how much growth remains.

Conclusion

Blount disease is a growth disorder affecting the upper shinbone and causing one or both legs to bow outward.

While bowed legs are common during early childhood and often correct naturally, progressive or asymmetrical bowing should not be ignored.

Early diagnosis helps doctors distinguish Blount disease from normal developmental bowing and other bone conditions.

Treatment may involve observation, bracing or surgery, depending on the child’s age and the severity of the deformity.

Pediatric physiotherapy plays a supportive role by improving strength, balance, walking ability and functional movement, particularly during recovery after treatment.

With appropriate orthopedic care and individualized rehabilitation, children can work towards better mobility and participation in everyday activities.

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