Blount's disease

Overview

Blount’s disease, also known as tibia vara, is a growth disorder that affects the bones of the lower leg, causing the tibia (shinbone) to angle inward, resulting in a bowlegged appearance. Unlike the normal bowing of legs seen in infants and toddlers, which typically corrects itself with age, Blount’s disease worsens over time and does not resolve without intervention. It can occur in young children (infantile Blount’s disease) or in adolescents (adolescent Blount’s disease), and it may affect one or both legs. Early diagnosis and treatment are crucial to prevent long-term deformity and mobility issues.

Causes

The exact cause of Blount’s disease is not fully understood, but it is thought to result from abnormal growth at the top of the tibia, near the knee. Risk factors and contributing factors include:

• Excessive mechanical stress on the growth plate of the tibia

• Early walking or bearing weight at a very young age

• Obesity – a significant risk factor, especially in adolescent Blount’s disease

• Genetics – family history may play a role

• Ethnicity – more commonly seen in children of African descent

Symptoms

Symptoms of Blount’s disease typically appear in early childhood or adolescence and may include:

• Visible bowing of one or both legs, worsening over time

• Asymmetry – one leg may appear more affected than the other

• Abnormal gait or limping

• Knee pain, especially with activity

• Leg length discrepancy in some cases

If left untreated, the deformity may continue to progress and lead to joint degeneration and mobility problems.

Diagnosis

Diagnosis of Blount’s disease involves a combination of clinical evaluation and imaging studies. Key diagnostic steps include:

• Physical examination – assessing the angle of leg bowing and gait pattern

• X-rays of the lower extremities – to evaluate the growth plates, tibial angle, and extent of deformity

• Measurement of mechanical axis deviation – to determine the degree of misalignment

• Monitoring over time – to distinguish Blount’s disease from physiological bowing that improves with age

Treatment

Treatment depends on the age of the patient and severity of the deformity. Options may include:

• Bracing – effective in young children under 3 years old with mild to moderate deformity; usually involves custom-made orthotic devices to guide normal growth

• Surgery – required in more advanced or progressive cases, or in older children and adolescents. Procedures may include:

  • Osteotomy – cutting and realigning the tibia

  • Growth modulation – using plates or screws to control growth of the growth plate

  • External fixation – in severe or complex cases requiring gradual correction

• Weight management – especially important in adolescent cases to reduce mechanical stress on the growth plate

• Physical therapy – post-operative rehabilitation to restore strength and mobility

Prognosis

With early diagnosis and appropriate treatment, the prognosis for children with Blount’s disease is generally favorable. Bracing is often successful in young children when initiated early. In more severe or untreated cases, long-term complications may include progressive deformity, joint instability, early-onset osteoarthritis, and chronic pain. Surgical correction can significantly improve limb alignment and function. Ongoing follow-up through growth years is essential to monitor for recurrence or new deformities.