Genu varus in detail according to orthopaedics text books

Reading File

Finding Sources

Reading File

Finding Sources

Reading File

Loading Image

Reading File

I now have comprehensive information from the orthopaedics textbooks. Let me compile the full detailed answer.

Genu Varus (Genu Varum) - Detailed Orthopaedic Review

Definition

Genu varus (also called genu varum, or "bow legs") is a deformity of the lower limb in the frontal (coronal) plane where the axis deviation causes the knee joint to be displaced lateral to the mechanical axis of the limb (the Mikulicz line). The tibia points toward the median line - i.e., the deformity is concave toward the vertical body axis.

Clinically, when the knees are separated and the medial malleoli are touching (feet together), an intercondylar distance greater than 3 cm is considered abnormal.

General Anatomy and Musculoskeletal System (THIEME Atlas of Anatomy)

Mechanical Axis and Biomechanics

The Mikulicz line (mechanical axis) normally runs from the center of rotation of the femoral head through the intercondylar eminence of the tibial plateau to the center of the ankle mortise. The anatomic and mechanical axes of the femur diverge at a 6-degree angle, making the femorotibial angle normally 174° at the knee (a laterally open angle).

In genu varum:

The center of the knee joint lies lateral to the mechanical axis
The medial joint complex is subjected to abnormal compressive pressure
The lateral structures (lateral collateral ligament, iliotibial tract, biceps femoris) are subjected to abnormal tension
Greater stress is placed on the lateral border of the foot, resulting in a fallen pedal arch
Progressive degenerative changes (medial compartment osteoarthritis) develop over time

THIEME Atlas of Anatomy - General Anatomy and Musculoskeletal System

Physiologic vs. Pathologic Genu Varum

Normal developmental progression (physiologic)

Progression of leg alignment from newborn to 4-6 years, showing physiologic genu varum resolving to straight legs

The above figure from Miller's Review illustrates the normal physiologic sequence:

Age	Alignment
Newborn	Moderate genu varum
1.5-2 years	Legs straight
2.5 years	Physiologic genu valgum
4-6 years	Legs straight (adult alignment)

Up to 20° of genu varum is considered normal during the first year of life
Physiologic genu varum normally evolves to genu valgum by age 2.5 years, with transition to physiologic valgus angulation by age 4
Radiographs in physiologic bowing show symmetric flaring of the tibia and femur
No treatment is needed for physiologic bowing

Pathologic Causes

Blount disease (tibia vara) - most common pathologic cause
Osteogenesis imperfecta
Osteochondromas
Trauma
Various skeletal dysplasias
Rickets (X-linked hypophosphatemic / vitamin D-resistant: defect in cellular endopeptidase, presents with short stature and genu varum, with physeal widening and metaphyseal cupping on radiographs)
Achondroplasia and other dwarfism syndromes (dwarfs with disproportionately short extremities tend to have genu varum)

Miller's Review of Orthopaedics, 9th Edition

Blount Disease (Tibia Vara) - The Most Important Pathologic Cause

History and Pathogenesis

Erlacher first described tibia vara (1922), but Blount's 1937 article gave the condition its name, describing it as "an osteochondrosis similar to coxa plana and Madelung deformity but located at the medial side of the proximal tibial epiphysis." It is now considered an acquired disease of the proximal tibial physis, not an epiphyseal dysplasia.

Exact cause is unknown, but the following factors are implicated:

Altered enchondral ossification
Hereditary and developmental factors (most likely combination)
Weight bearing is required - does not occur in non-ambulatory patients
Strongly associated with early walking and obesity
Rising incidence linked to the "obesity epidemic" and vitamin D deficiency

The abnormality is characterized by:

Varus and internal torsion of the tibia
Genu procurvatum

Types of Blount Disease

Infantile Blount Disease (age 0-8 years)

Begins before age 8
Bilateral and symmetric in 60% (vs. physiologic bowing which is 100% bilateral)
Progressive varus (vs. physiologic bowing which resolves with growth)
Difficult to differentiate from physiologic bowing at <2 years
Classic presentation: overweight child who begins walking before 1 year of age, associated with internal tibial torsion
More common overall

Adolescent Blount Disease (late onset)

Less severe than infantile forms
More often unilateral
Epiphysis appears relatively normal - no beaking as seen in infantile type
Most characteristic radiographic finding: widening of the proximal medial physis
Thought to result from mechanical overload in genetically susceptible patients (obese, Black individuals)
A variant ("obesity-related Blount") shows dome-shaped metaphysis, open growth plate, and inferomedial translation of the proximal tibial epiphysis

Radiographic Assessment

Key Radiographic Findings (Infantile Blount)

Medial half of proximal tibial epiphysis is short, thin, and wedged
Physis is irregular in contour and slopes medially
Proximal metaphysis forms a palpable medial projection
Medial metaphyseal fragmentation is pathognomonic for progressive tibia vara
Angular deformity occurs just distal to the medial projection

MRI Additional Findings

Increased thickness of the chondroepiphysis of the proximal medial tibia
Increased height and width of the medial meniscus
Abnormal medial femoral epiphysis

Measurement Tools

1. Drennan Metaphyseal-Diaphyseal Angle

Lines drawn along the longitudinal axis of the tibia and through the metaphyseal beaks
>11-16 degrees = abnormal (classic Drennan threshold is >16°)
A Drennan angle >16° strongly suggests tibia vara over physiologic bowing

2. Tibiofemoral Angle

Lines drawn along the longitudinal axes of the tibia and femur
In Blount disease, the tibiofemoral angle does not progress normally from varus to valgus between 1.5-3 years

3. Mechanical Axis (Long-Film Radiograph)

Most functional measurement of the amount of deformity
Standing long-film radiographs recommended
Femoral varus of 10 degrees more than the calculated ideal femoral-tibial joint angle represents 34-76% of the genu varum deformity

Langenskiöld Classification (Infantile Blount)

The Langenskiöld classification describes six stages based on progressive epiphyseal-metaphyseal changes. At stage VI, the medial portion of the epiphysis fuses at a 90-degree downward angle - the most severe form.

Treatment

Physiologic Genu Varum

Observation only - resolves spontaneously
No bracing or surgery needed

Infantile Blount Disease

Stage / Age	Treatment
Children aged 2-3 years, Stage I-II	Observation or KAFO bracing (knee-ankle-foot orthosis)
Children >3 years, Stage II-III	Proximal osteotomy of tibia/fibula with valgus angulation (mild overcorrection)
Stages IV-VI	Complex - multiple procedures may be needed; epiphysiolysis for stages V-VI

Key surgical principle: Valgus osteotomy of the proximal tibia and fibula with mild overcorrection is recommended in young children (<4 years), because medial physeal growth abnormalities persist.

Recurrence rates:

Children >4 years: 80-90% recurrence after osteotomy
Children <4 years: <20% recurrence

Guided Growth (Emerging Technique)

Temporary epiphysiodesis using tension band plates (eight-plate technique)
Lateral guided growth correction based on the Hueter-Volkmann law (growth is decreased by compression; returns when compression is removed)
Minimally invasive vs. osteotomy
~12% implant failure rate requiring return to OR
Growing evidence supports use at earlier ages

Adolescent Blount Disease

First-line when growth remains: Proximal tibial and fibular lateral hemiepiphysiodesis
Larger plates usually required (due to plate failure incidence in obese patients)
If physes are closed or residual deformity exists: tibial and fibular osteotomy
Ilizarov technique for deformity correction + lengthening when significant LLD is present

Osteotomy Techniques

Proximal Tibial Osteotomy for Genu Varum

Oblique osteotomy (Rab technique):

Begins distal to the tibial tubercle, through a transverse cosmetic incision
An oblique osteotomy directed anterodistal to posteroproximal simultaneously corrects varus and internal rotation
In Blount disease, patients have approximately equal amounts of varus and internal rotation
A 45-degree upward osteotomy provides adequate correction in most patients
Post-operative cast wedging possible since no rigid internal fixation

Other techniques:

Crescent-shaped chevron osteotomy (Greene) - maintains limb length
Hemicondylar tibial osteotomy (Zayer) through the epiphysis into the intercondylar notch - corrects posteromedial slope of the tibial epiphysis

External Fixation

Uniplanar external fixator: easy to apply, adjustable, allows early weight bearing, avoids second operation
Hexapod-based (Ilizarov-type) systems: preferred for obese patients with complex multi-plane deformities; allows computer-navigated correction of residual deformity post-operatively
Excellent correction with good safety profile

Neurovascular Complications

Peroneal nerve palsy
Vascular occlusion (anterior tibial artery compression occurs with valgus correction; stretching occurs with varus correction at the interosseous membrane)

Genu Varum in the Context of Arthritis

In the adult knee, genu varum leads to medial compartment overload and eventual medial compartment osteoarthritis. The "triple varus knee" (Noyes) describes:

Genu varum alignment
Soft-tissue varus instability
Lateral/varus thrust in the stance phase of ambulation

This is the most advanced form requiring combined bony and soft-tissue reconstruction.

Summary Table

Feature	Physiologic	Infantile Blount	Adolescent Blount
Age	<2 years	<8 years	>8 years
Bilaterality	100%	60%	Usually unilateral
Progression	Resolves	Progressive	Variable
Drennan angle	<11°	>11-16°	(Less reliable)
Epiphyseal beaking	Absent	Present	Absent
Medial physis changes	Absent	Fragmentation	Widening
Treatment	Observation	KAFO → osteotomy	Hemiepiphysiodesis → osteotomy

Sources:

Miller's Review of Orthopaedics, 9th Edition - Chapter on Leg/Knee
Campbell's Operative Orthopaedics, 15th Ed 2026 - Tibia Vara (Chapter 34)
THIEME Atlas of Anatomy - General Anatomy and Musculoskeletal System - Mechanical Axis sections

This is a shared conversation. Sign in to Orris to start your own chat.