Comprehensive examination of lower limb alignment in children including assessment of genu varum/valgum, in-toeing/out-toeing, leg length discrepancy, and differentiation of physiological from pathological variants.
Lower limb alignment examination in children requires understanding of normal developmental variation. Examiners expect you to differentiate physiological from pathological conditions, measure angular and rotational profiles, and know when investigation is warranted.
High-Yield Exam Summary
Normal Development:
Key Point: Most angular deformities in toddlers are physiological and will correct spontaneously.
When to Worry About Angular Deformity:
Position:
Varus (Bow-Legged) Assessment:
Valgus (Knock-Knee) Assessment:
Quantify genu varum
Distance greater than 6cm after age 2 years
Excessive genu varum - consider Blount's disease, rickets, or skeletal dysplasia
Ability to detect true positives
Ability to exclude false positives
Quantify genu valgum
Distance greater than 8cm at any age
Excessive genu valgum - usually physiological if bilateral and symmetric
Ability to detect true positives
Ability to exclude false positives
Components of Rotation:
Foot Progression Angle (FPA):
Causes by Level:
1. Metatarsus Adductus (Foot Level):
2. Internal Tibial Torsion:
3. Femoral Anteversion:
Most Common: 3-6 years = increased femoral anteversion
Assess femoral version
Internal rotation greater than 70° with external rotation less than 20°
Increased femoral anteversion (common cause of in-toeing in 3-6 year olds)
Ability to detect true positives
Ability to exclude false positives
Assess tibial torsion
Negative angle (foot points inward relative to thigh)
Internal tibial torsion (common cause of in-toeing in 1-3 year olds)
Ability to detect true positives
Ability to exclude false positives
True vs Apparent LLD:
Causes:
Clinical Significance:
Measure leg length discrepancy
Measured block height indicates LLD
True leg length discrepancy if pelvis levels with blocks
Ability to detect true positives
Ability to exclude false positives
Technique:
Interpretation:
Limitation:
| condition | age | pattern | features | action |
|---|---|---|---|---|
| Physiological Varus | 0-2 years | Bilateral, symmetric | Normal development | Observe, reassure |
| Blount's Disease | Greater than 2 years | Unilateral or asymmetric | Varus increasing, lateral thrust | X-ray, brace or surgery |
| Rickets | Any | Bilateral, may be asymmetric | Multiple metaphyseal changes, short stature | Bloods, X-ray, treat cause |
| Physiological Valgus | 2-7 years | Bilateral, symmetric | Maximum at 4 years, improving | Observe, reassure |
| Pathological Valgus | Greater than 8 years or progressive | May be unilateral | IM distance greater than 8cm, progressive | Investigate underlying cause |
Blount's Disease (Tibia Vara):
Observe:
Running:
Stairs (if age appropriate):
"18-month-old child brought by parents concerned about 'bow-legs' - worried child will never walk normally."
High-Yield Exam Summary