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Knee Angular Deformities: Genu Valgum, Genu Varum & Genu Recurvatum

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1. Anatomical & Biomechanical Foundations

The Mechanical Axis (Mikulicz Line)

• The anatomical axis of the femur and the mechanical axis diverge by ~6°
• The longitudinal anatomical axes of femur and tibia form a laterally open angle of 174° at the knee (femorotibial angle)
• Any deviation shifts joint loading abnormally — progressive cartilage and bone degeneration follows

General Anatomy and Musculoskeletal System (THIEME Atlas), p. 431

General Anatomy and Musculoskeletal System (THIEME Atlas), p. 46

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2. Genu Varum (Bow Legs)

Definition

Normal vs. Pathologic

Miller's Review of Orthopaedics 9th Ed., p. 277

Types / Causes

Biomechanical Consequences

• Mechanical axis passes medial to knee → medial compartment overloaded (compression)
• Lateral structures (lateral collateral ligament, iliotibial band, biceps femoris) under abnormal tension
• Greater stress on the lateral border of the foot → fallen pedal arch
• Long-standing varus → medial compartment osteoarthritis

THIEME Atlas, p. 431

Diagnostic Criteria (Orthopaedic)

• Clinical: intercondylar distance >3 cm with feet together = abnormal
• Radiograph (weight-bearing full-length): mechanical axis passes medial to knee; Drennan angle >16° for Blount
• Pathologic if: asymmetric, persists beyond age 2, associated with short stature (<10th centile), pain, or prior infection/trauma

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3. Genu Valgum (Knock Knees)

Definition

Normal vs. Pathologic

Miller's Review of Orthopaedics 9th Ed., p. 278

Types / Causes

Biomechanical Consequences

• Mechanical axis passes medial to knee centre → lateral compartment overloaded
• Medial structures (MCL) under tension/elongation
• Increased patellofemoral lateral pressure → anterior knee pain, patellar instability
• Increased Q-angle → lateral patellar tracking dysfunction
• Lateral compartment OA in chronic cases

Diagnostic Criteria (Orthopaedic)

• Clinical: intermalleolar distance >5 cm (THIEME) or >8 cm (StatPearls) with medial femoral condyles touching = abnormal
• Q-angle >10° indicates valgus malalignment
• Radiograph (weight-bearing full-length): mechanical axis medial to knee centre; valgus angulation measured at tibiofemoral joint
• Surgical threshold (children): >10 cm intermalleolar distance OR >15° valgus angulation in children >10 years

Miller's Review of Orthopaedics 9th Ed.; THIEME Atlas, p. 431

Orthopaedic Management

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4. Genu Recurvatum (Back Knee / Hyperextension)

Definition

Types / Causes

Miller's Review of Orthopaedics 9th Ed.; Imaging Anatomy Atlas Vol. 3

Biomechanical Consequences

• The oblique popliteal ligament is the primary restraint to recurvatum — its failure is central to pathologic hyperextension
• Weight line shifts anterior to knee axis → posterior capsule and cruciate ligaments under chronic tensile stress
• Quadriceps function at disadvantage — passive hyperextension substitutes for active extension
• Compensatory lumbar hyperlordosis and anterior pelvic tilt common

General Anatomy and Musculoskeletal System (THIEME Atlas), p. 522

Diagnostic Criteria (Orthopaedic)

• Clinical: knee extension beyond 0° (normal extension = 5–10° hyperextension is borderline); pathologic if >10–15° or symptomatic
• Associated with: positive posterior drawer, PCL/posterolateral corner laxity
• Gait analysis: characteristic "back-kneeing" gait pattern
• Neurological assessment to exclude quadriceps weakness as primary cause
• MRI to evaluate posterior capsule, oblique popliteal ligament, PCL

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5. Clinical Assessment Summary

Physical Examination Protocol

Radiographic Assessment

• Weight-bearing full-length AP radiograph (hip to ankle) — gold standard
• Measures: mechanical axis deviation, tibiofemoral angle, Drennan angle (Blount)
• Low-dose biplanar systems (EOS imaging) increasingly used
• CT scanogram for limb length discrepancy

Grainger & Allison's Diagnostic Radiology

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6. Role of Physiotherapy

A. Genu Valgum — Physiotherapy

• Single-leg band stretches (hip abductor strengthening)
• Leaning ankle band stretches (hip flexor stretch + ankle stabilisation)
• Resistance band squats (quadriceps + hip abductor co-activation)
• Step-down with knee alignment cues (neuromuscular re-education)

Physiopedia — Valgus Knee

B. Genu Varum — Physiotherapy

C. Genu Recurvatum — Physiotherapy

THIEME Atlas of Anatomy — Knee Muscle Function, p. 522–523

Orthotics & Adjuncts in Physiotherapy

• Medial wedge insoles (genu varum): shift load laterally
• Valgus unloader brace (medial compartment OA + varum)
• Knee immobiliser / hyperextension brace (recurvatum with ligamentous laxity)
• Kinesio taping — patellar tracking (valgum), quadriceps facilitation (recurvatum)

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7. Orthopaedic Decision Algorithm

Angular deformity detected
        ↓
Age-appropriate physiologic? → YES → Observe, review 6–12 monthly
        ↓ NO
Identify cause (metabolic, trauma, infection, dysplasia)
        ↓
Treat underlying condition
        ↓
Persistent / progressive / pain / LLD?
        ↓
Skeletally immature → Guided growth (hemiepiphysiodesis)
Skeletally mature  → Corrective osteotomy
End-stage OA       → TKR / UKR

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Summary Table

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