Genu Valgum and Genu Varum in Children

Angular knee deformities are common presenting concerns in pediatric orthopaedics. Understanding the normal physiological development is essential to differentiate benign patterns from pathological conditions requiring intervention.

Definitions:

• Genu varum: "Bowlegs" - tibiofemoral angle in varus, knees apart when ankles together
• Genu valgum: "Knock-knees" - tibiofemoral angle in valgus, ankles apart when knees together

Epidemiology:

• Physiological angular deformity is extremely common and usually normal
• Infantile Blount disease: more common in African descent, early walkers, obese
• Rickets: nutritional form rare in developed countries; renal osteodystrophy in chronic kidney disease

Lower Limb Mechanical Axis

Physeal Growth and Correction

Key Radiographic Measurements:

• Mechanical axis deviation (MAD): Distance from mechanical axis to knee center
• Metaphyseal-diaphyseal angle (MDA): Described by Levine and Drennan (original threshold over 11°); the higher cut-off of over 16° popularised by Feldman and Schoenecker is the modern working value suggesting Blount disease, with an indeterminate grey zone between 9° and 16°
• Tibial metaphyseal angle: Assesses tibia vara severity
• Epiphyseal-metaphyseal angle (Gordon): Adjunct that may improve early discrimination of Blount disease from physiological bowing

Post-Osteotomy Rehabilitation:

• Protected weight-bearing for 6-8 weeks
• Knee ROM exercises
• Progress to full weight-bearing and activity

Physiological Deformity: Near-universal spontaneous resolution; no intervention needed in the vast majority.

Guided Growth: High success rate in appropriate candidates with predictable correction, low morbidity, and reversibility if overcorrection occurs.

Blount Disease: Infantile disease has a better prognosis when treated early; adolescent disease shows higher recurrence and often needs osteotomy. Residual malalignment carries a long-term risk of medial compartment osteoarthritis.

Angular knee deformity is a high-volume but evidence-thin area: most data are retrospective single-centre series, and several practical questions remain genuinely unsettled. Examiners reward a candidate who can state what is established versus what is debated.

Documentation Points:

• Age, height, and clinical measurements (ICD/IMD)
• Gait assessment including lateral thrust
• Family history and dietary assessment
• Radiographic findings and measurements

Consent for Surgery:

• Need for hardware removal after correction
• Risk of overcorrection or undercorrection
• May need additional surgery (recurrence, other side)
• Osteotomy risks: compartment syndrome, nerve injury

Global Epidemiology:

• Physiological angular variation is near-universal in toddlers and is the single commonest reason for paediatric orthopaedic referral for "bent legs"; the vast majority require only reassurance.
• Infantile Blount disease shows a higher reported prevalence in populations of African ancestry, in early walkers, and with rising childhood obesity; late-onset (adolescent) Blount tracks closely with the global obesity epidemic.
• Nutritional rickets remains an important and preventable cause worldwide, concentrated in infants with darker skin, limited sun exposure, exclusive prolonged breastfeeding without supplementation, and low dietary calcium; X-linked hypophosphataemic rickets and renal osteodystrophy are the main non-nutritional metabolic causes.

Guidelines, Side by Side:

There is broad international agreement on the principles (observe physiological deformity, screen for metabolic causes in bilateral deformity, prefer guided growth while the physis is open) and no major society-level disagreement on the core algorithm — the genuine debates are technical (thresholds, timing) rather than national.

Registry and Outcome Notes:

• There is no dedicated paediatric angular-deformity arthroplasty registry; evidence is from institutional series and multicentre study groups rather than national joint registries.
• Long-term registry-style follow-up matters because residual malalignment is a recognised risk factor for early medial compartment osteoarthritis, linking childhood correction to adult arthroplasty burden captured in national joint registries.

High- vs Limited-Resource Practice Variation:

• Well-resourced settings: standing long-leg radiographs, MRI for physeal-bar assessment, tension-band plating and computer-assisted/hexapod external fixators are routinely available.
• Limited-resource settings: the priority shifts to public-health prevention of nutritional rickets (supplementation, fortification), clinical screening without long-leg films, and definitive osteotomy where staged guided growth or repeat hardware procedures are impractical.
• Parental concern is often driven by cultural norms about leg shape; clear reassurance about the physiological arc prevents unnecessary imaging and intervention everywhere.