Blount’s Disease

What is Blount’s Disease?

Blount’s disease is a progressive growth disorder of the proximal tibial physis, leading to pathologic bowing (genu varum) of the legs. It occurs due to excessive compressive forces inhibiting growth of the medial proximal tibial physis, while the lateral physis continues growing normally.

Incidence and Risk Factors

• Infantile Blount’s disease (≤3 years): More common, bilateral, linked to early walking and obesity.
• Adolescent Blount’s disease (>10 years): Unilateral, associated with obesity, trauma, or rapid growth spurts.
• Higher prevalence in African American children and those with early weight-bearing activities.

Causes and Pathophysiology

The medial proximal tibial growth plate experiences chronic excessive mechanical stress, leading to growth suppression, varus deformity, and tibial internal rotation.

Clinical Features

• Progressive bowing of the legs (more pronounced than physiologic bowing)
• Medial knee pain (especially in adolescent-onset cases)
• Internal tibial torsion and in-toeing gait
• Limb length discrepancy in severe cases

Evaluation and Diagnosis

• Standing AP X-rays (knee and full-length lower limb):
  • Tibial varus deformity
  • Metaphyseal-diaphyseal angle >11° (diagnostic threshold)
  • Medial beaking and sloping of the proximal tibial epiphysis
• MRI: Helpful in differentiating from other causes of genu varum, such as rickets or skeletal dysplasias.

Treatment Options

Non-Surgical (Bracing) for Infantile Blount’s Disease

• Knee-ankle-foot orthosis (KAFO):
  • Indicated if detected before age 3 years
  • Goal: Reduce medial tibial stress and allow normal growth
  • Effective only in mild cases (<16° deformity)

Surgical Treatment

Indicated in progressive or severe cases, including:

1. Guided growth (Hemiepiphysiodesis)
   • Temporary growth modulation (using tension plates or staples)
   • Performed in children with remaining growth potential
2. Tibial osteotomy
   • Acute or gradual correction (via external fixators like Ilizarov)
   • Indicated in adolescents or severe deformities (>20° varus)
3. Physeal bar resection (rare cases)
   • Used if there is focal growth arrest in the medial physis

Complications

• Progressive deformity and joint instability if untreated
• Knee osteoarthritis due to abnormal load distribution
• Leg length discrepancy

Prognosis

• Infantile Blount’s disease: Excellent prognosis if treated early with bracing or surgery.
• Adolescent Blount’s disease: Often requires surgical correction, but outcomes are favorable with timely intervention.

References

1. Sabharwal S, et al. Update on Blount’s disease. J Pediatr Orthop. 2019;39(4):219-228.
2. Birch JG. Blount’s disease: Etiology and management. J Am Acad Orthop Surg. 2013;21(7):408-418.
3. Gordon JE, et al. The treatment of Blount’s disease: A comprehensive review. J Pediatr Orthop. 2006;26(5):695-707.