What is the medical term for being born with bowed legs?

Genu Varum: The Medical Term for Bowed Legs

Genu varum is the medical term for being born with bowed legs, a condition where the legs curve outward at the knees. 1

Understanding Genu Varum

Genu varum is characterized by a varus deformity where the distal part of the leg is deviated inwards in relation to the femur, resulting in a bow-legged appearance 1. This condition can be classified into two main categories:

Physiologic Genu Varum

• Normal developmental pattern: Infants are commonly born with bowed legs as part of normal development 2
• Age of presentation: Most noticeable when children begin walking (around 10-12 months) 2
• Natural history: Typically resolves spontaneously with growth 3
• Resolution timeline:
  • Children presenting before 18 months: Initial correction between 18-24 months, resolution by 30 months
  • Children presenting between 18-23 months: Initial correction between 24-30 months, resolution by 36 months 2

Pathologic Genu Varum

Pathologic causes require medical intervention and include:

1. Metabolic disorders:

   • X-linked hypophosphataemia 1
   • Rickets
   • Renal osteodystrophy

2. Skeletal dysplasias:

   • Achondrogenesis
   • Osteogenesis imperfecta 4

3. Other causes:

   • Tibia vara (Blount's disease) - the most common pathologic condition 4
   • Previous trauma affecting growth plates
   • Infections affecting growth plates 5

Diagnostic Approach

Clinical Assessment

• Measure intermalleolar distance (distance between inner ankles when knees are touching)
• Assess gait pattern
• Evaluate for associated symptoms like pain or functional limitations
• Document developmental milestones (children with physiologic genu varum often walk earlier than average - around 10 months vs. 12-15 months) 2

Imaging

• Weight-bearing radiographs are essential for evaluating the mechanical axis of the limb 5
• Include anteroposterior (AP) projection of the hip, knee, and ankle with calibration rule
• Limited value in children under 4 years due to incomplete ossification 5

Management

Physiologic Genu Varum

• Observation is the mainstay of treatment for physiologic bowing 3
• Regular follow-up to monitor progression or resolution:
  • For children presenting before 18 months: Follow-up at 24 and 30 months
  • For children presenting between 18-23 months: Follow-up at 30 and 36 months 2

Pathologic Genu Varum

• Treatment depends on underlying cause, severity, and age of the patient
• Metabolic causes: Treat the underlying condition (e.g., vitamin D supplementation for rickets)
• Blount's disease: May require bracing or surgical intervention depending on severity and age
• Skeletal dysplasias: Management is often multidisciplinary and condition-specific

When to Refer to Orthopedics

• Bowing that persists beyond expected age of resolution (typically after 3 years)
• Progressive deformity
• Asymmetric bowing (one leg more affected than the other)
• Associated pain or functional limitations
• Suspected underlying pathologic condition
• Significant deformity affecting gait 5

Important Considerations

• Orthotics or shoe inserts are not recommended for the management of genu varum in children 5
• Standing radiographs of the entire lower limbs are necessary for surgical planning, as the deformity can sometimes affect the distal femur rather than the proximal tibia 4
• Persistent pathologic genu varum can lead to long-term biomechanical problems, including joint pain, premature arthritis, and gait alterations 5

Genu varum should be distinguished from genu valgum (knock-knees), which is characterized by inward angulation of the knees, as the management approaches differ significantly.