X-Ray Evaluation for Bowlegged Children Under 2 Years Old
X-rays are generally not necessary for children under 2 years old with bowleggedness, as physiologic genu varum is normal and expected at this age and typically resolves spontaneously. 1
Understanding Normal Development vs. Pathology
Physiologic bowing is a normal developmental process in children under 2 years of age and represents the expected lower extremity alignment during early walking years. 1
The vast majority of bowlegged appearance in this age group resolves spontaneously without intervention, making it crucial to avoid unnecessary radiation exposure. 1, 2
After age 2 years, any significant residual bowing becomes abnormal and warrants radiographic evaluation to distinguish pathologic conditions from physiologic variants. 1
When X-Rays Are NOT Indicated (Most Cases Under Age 2)
Children under 2 years with symmetric, mild-to-moderate bowing and normal development do not require radiographic screening. 1, 2
The difficulty in differentiating physiologic bowlegs from early infantile Blount's disease in children aged 11-30 months is well-documented, and early radiographic measurements (including tibial-femoral angle and metaphyseal-diaphyseal angle) have proven unreliable for making this distinction. 2
A retrospective study demonstrated that all patients with severe bowing in early infancy recovered spontaneously, questioning whether infantile Blount's disease can even be reliably diagnosed before age 2. 2
When X-Rays ARE Indicated (Red Flags)
Obtain standing anteroposterior radiographs of both lower extremities if any of the following are present:
Unilateral bowing (asymmetric involvement suggests pathology rather than physiologic variant). 3
Progressive worsening of the bowing deformity rather than improvement over time. 1
Severe obesity with early walking onset (BMI ≥22 kg/m² significantly increases risk for infantile Blount's disease). 4
Age approaching or exceeding 2 years with persistent significant bowing. 1, 5
Associated findings such as short stature, skeletal dysplasia features, or systemic symptoms suggesting metabolic bone disease. 3
Clinical Assessment Priorities
Document the child's BMI and age of walking onset, as obesity combined with early ambulation represents the primary risk factor for pathologic tibia vara. 4
Assess for symmetry of involvement, as physiologic bowing is typically bilateral and symmetric. 3
Observe the child's gait and weight-bearing pattern for functional limitations. 1
Evidence-Based Screening Approach for Ages 2-3 Years
If radiographs are obtained (typically after age 2), the combination of tibial metaphyseal-diaphyseal angle (TMDA) ≥10 degrees AND epiphyseal-metaphyseal angle (EMA) >20 degrees identifies children at high risk for Blount's disease with 95% sensitivity and 100% specificity. 5
Children with TMDA <10 degrees are at minimal risk and can be observed clinically. 5
Children with TMDA ≥10 degrees but EMA ≤20 degrees remain at lower risk and require close clinical follow-up without immediate intervention. 5
Critical Pitfalls to Avoid
Do not obtain radiographs routinely in children under 2 years with symmetric bowing, as this exposes them to unnecessary radiation for a condition that typically resolves spontaneously. 1, 2
Avoid over-relying on single radiographic measurements in children under 2 years, as these have poor predictive value for distinguishing physiologic from pathologic bowing at this age. 2
Recognize that BMI ≥22 kg/m² is the strongest clinical predictor for development of infantile Blount's disease and should lower your threshold for obtaining radiographs and providing nutritional counseling. 4
Do not assume all bowing requires treatment—the natural history favors spontaneous resolution in the vast majority of cases under age 2. 1, 2