Blount Disease (Tibia Vara)

What it is. Blount disease (tibia vara) is a pathologic growth disturbance of the medial side of the proximal tibial physis: endochondral ossification fails at the medial metaphysis and the limb bows into progressive genu varum. Untreated it progresses to permanent deformity, a lateral thrust gait, medial compartment osteoarthritis and functional disability.

Two diseases under one name. The infantile form, the more common, begins before age 4 in a child who often walked early, is bilateral in 60-80%, and is the form that may still answer to a brace. The adolescent form begins after 8-10 years, is unilateral in 80%, is tied to obesity, and is less predictable and worse in prognosis: it needs surgery.

Who gets it. Prevalence varies markedly by population: higher in children of African and Afro-Caribbean descent and in regions where infants walk early, and relatively rare in Northern European and Caucasian populations. Boys outnumber girls about 3:1, and incidence is rising worldwide in parallel with childhood obesity, especially the adolescent form.

Risk factors. Two are mechanical and familiar: walking before 10 months, and obesity, which matters most in the adolescent form and where BMI is an independent predictor of being listed for surgery. The rest are African or Hispanic descent, vitamin D deficiency (controversial), and mechanical stress on the immature medial physis.

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Normal growth at the knee. The proximal tibial physis contributes 55-60% of tibial growth, and its medial and lateral halves should grow symmetrically, about 6mm per year overall. Growth velocity peaks in infancy and again in early adolescence.

Normal alignment moves with age. A newborn stands in 10-15° varus, the mechanical axis is neutral at 12-18 months, swings to 10-12° valgus between 2 and 4 years, and settles at the adult 5-7° valgus by 6-7 years. Physiologic bowing follows that curve and resolves by age 2-3; a knee that stays varus, or worsens, past that point is the one to worry about.

The mechanical axis. A line from the centre of the femoral head to the centre of the ankle normally passes through, or just lateral to, the medial tibial spine. In Blount disease it passes medial to the knee, so the medial compartment carries more of the load.

Hueter-Volkmann is the engine. Increased compression across a physis decreases growth; decreased compression increases it. Mechanical overload of the medial physis therefore suppresses medial growth, the knee drifts further into varus, and the varus raises medial stress again. The cycle does not break on its own.

What the physis becomes. Histology shows disorganised architecture with loss of the columnar arrangement, fibrocartilaginous tissue replacing normal physeal cartilage, a thickened medial periosteum, and islands of cartilage left in the metaphysis where resorption has failed. The physis is not necrotic, it is replaced, and the changes deepen from Stage I to Stage VI.

What adds to the load. Early walking increases medial compartment stress, obesity dramatically increases joint reaction forces, and internal tibial torsion increases the frontal-plane moment arm, loading the medial physis asymmetrically.

What the deformity is made of. Varus angulation is the primary deformity, and the rest accumulate around it:

• Internal tibial torsion in 60-80% of cases
• Procurvatum, anterior bowing, in advanced cases
• A medial physeal bar at Stage VI
• Leg length discrepancy from asymmetric growth

Procurvatum is the plane that hides. Apex-anterior bowing of the proximal tibia with an increased posterior tibial slope develops in advanced and adolescent cases, particularly in heavier children, and procurvatum correlates with BMI in early-onset disease. The AP radiograph does not show it, so it has to be sought on the lateral standing film. A purely frontal-plane valgus osteotomy that ignores it leaves residual sagittal malalignment, which is why significant procurvatum calls for a dome osteotomy or a circular frame that corrects varus, torsion and procurvatum together.

There are two levels of deformity, not one. In advanced infantile and adolescent disease the medial tibial plateau itself becomes depressed: the medial joint surface slopes downward medially, producing joint-line obliquity and medial articular incongruity, which is LaMont's type C lesion. A standard metaphyseal osteotomy does not address it.

Why that matters. Correct the metaphysis alone and the limb can look aligned on the film while the joint stays incongruent and the lateral thrust persists, which sets up recurrence and early medial osteoarthritis.

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What a medial hemiplateau elevation actually is

The problem it solves. In advanced disease - Langenskiöld V-VI in an older child - the posteromedial tibial plateau is depressed, so the articular surface slopes medially downward and the deformity sits inside the joint rather than in the shaft. A proximal tibial metaphyseal osteotomy can restore the mechanical axis and still leave the joint line sloped, so the knee stays incongruent, keeps its medial thrust, and tends to recur and degenerate.

The procedure. An intra-epiphyseal (intra-articular) osteotomy that elevates the depressed posteromedial plateau back to a level articular surface, grafting the metaphyseal void created beneath it. It is almost always combined:

• with a proximal tibial metaphyseal valgus/derotation osteotomy to correct the limb axis, and
• with a lateral proximal tibial hemiepiphysiodesis to stop the lateral physis re-creating varus, and/or medial physeal bar resection

Who needs it. The older child, roughly over 7 to 8 years, with advanced disease and a fixed intra-articular medial slope that metaphyseal realignment alone cannot correct. Assess joint-line obliquity on the standing film or MRI before planning. Its precise role and timing remain debated; see Controversies.

How they present. Parents bring a child whose bowed legs are not improving, or are visibly worsening, often with an abnormal gait - waddling, or thrusting outward - and sometimes with lateral wear on the shoe soles. Knee or leg pain belongs to the older child and is uncommon in the infantile form. The infantile form declares itself between 18 months and 3 years, once walking is established; the adolescent form between 8 and 15 years, often at the growth spurt.

The history that changes management. Ask when the child first walked, because walking before 10 months is a risk factor, and ask about birth weight and current weight. Then establish whether the deformity is unilateral or bilateral and whether it is progressing or static, and take a family history of bowed legs or metabolic bone disease, a dietary history for vitamin D and calcium, and a record of any previous bracing or treatment.

Red flags for another diagnosis. Short stature or involvement of other joints points to a skeletal dysplasia, pathologic fractures to rickets or another metabolic bone disease, and developmental delay to a genetic syndrome.

Physical Examination

Watch them walk first. The lateral thrust - a dynamic varus thrust during stance - is the finding that matters: it means the medial compartment is functionally insufficient, and it predicts progression. Bilateral disease waddles, with reduced cadence and stride length.

Standing alignment. Measure the intercondylar distance between the medial femoral condyles with the ankles together: under 6cm is normal in a young child, and over 6-8cm suggests pathologic bowing. In unilateral disease compare knee heights for asymmetry.

Rotation. Internal tibial torsion is read from the thigh-foot angle, normally about 10 degrees external. Check femoral version by internal rotation with the child prone.

The rest of the knee and limb. Increased medial gapping on varus stress means LCL laxity from chronic lateral stretch, while a varus that will not correct is bony and belongs to advanced disease. Measure true leg length from ASIS to medial malleolus, since medial overgrowth and asymmetric growth produce discrepancy, and record knee range, ligament stability and neurovascular status, excluding a neuromuscular disorder.

The general examination. BMI with height and weight percentiles, and a deliberate look for the signs of rickets - widened wrists, costochondral beading - or of a skeletal dysplasia.

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Genu varum in a child has a short differential, of which physiologic bowing is by far the most common, and the examiner will expect you to work through it before settling on Blount disease. Age and the MDA separate physiologic bowing from Blount disease; biochemistry, the pattern of skeletal involvement and the history separate the others.

Algorithm

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The decision rests on three things: age, Langenskiöld stage and the MDA. Age under 3 years is the critical factor for bracing success, and Stage IV or higher is operative whatever the age.

Non-OperativeSurgical Indications & TimingSurgical OptionsPost-Operative Care

Observation is for physiologic genu varum - under 2 years with an MDA under 11 degrees - and for the borderline child with an MDA of 11-16 degrees. Review clinically and radiographically every 6 months, watching for a rising MDA or an advancing Langenskiöld stage, and counsel on the natural history and on weight.

Bracing: every criterion has to be met.

• Infantile Blount disease, onset before age 4
• Age under 3 years, preferably 1-3 years
• Langenskiöld Stage I or II, occasionally Stage III if the child is very young
• MDA 11-16 degrees (some authorities include up to 20 degrees)
• A compliant family, because the brace is worn 23 hours a day

Age over 3-4 years, Stage IV or higher, the adolescent form and a fixed deformity are contraindications.

The orthosis and the protocol. A custom-moulded KAFO running from upper thigh to ankle and delivering a valgus force, worn 23 hours a day with removal for bathing only, for 12-24 months, reviewed clinically and radiographically every 3-4 months. Night-time bracing alone does not work.

What success looks like. The MDA falls by 5 degrees or more, the tibiofemoral angle loses varus and the stage does not advance, with an MDA under 11 degrees as the target.

What failure looks like. The MDA progresses despite 6-12 months of bracing, the Langenskiöld stage advances, the child reaches 4 years without improvement, or the brace is not being worn. Any of these converts the plan to surgery.

The numbers. Bracing corrects 60-80% of Stage I-II disease under age 3, 20-40% of Stage III, and essentially none of Stage IV disease or of older children. Those figures come from series with differing stage mixes and compliance, and no randomised comparison of bracing against observation exists.

Caution

Recognise a failing brace early

Non-compliance is the commonest reason bracing fails, so judge before you start whether the family can deliver 23 hours a day. Persevering past the point of failure gains nothing and delays definitive surgery in a child whose window for correction is closing.

Absolute indications.

• Langenskiöld Stage IV or higher (medial metaphyseal overgrowth)
• Failed bracing after 6-12 months in an appropriate candidate
• Age over 4 years at presentation, when bracing is unlikely to succeed
• Adolescent Blount disease - every case
• Progressive deformity with functional impairment, meaning a lateral thrust gait

Relative indications are Stage III approaching age 4, an MDA over 20 degrees even in a young child, severe mechanical axis deviation, and unilateral disease.

What the operation is for. Correcting the varus and restoring the mechanical axis, addressing the internal tibial torsion, correcting procurvatum, restoring symmetric physeal growth in a child who is still growing, and preventing recurrence.

Timing is a trade between remodelling and recurrence. The younger the child, the better the remodelling and the worse the recurrence:

• Under 4 years: optimal remodelling but recurrence of 30-50%. Overcorrect to 10 degrees valgus, counsel the family that repeat surgery is likely, and consider gradual correction with an external fixator
• Age 4-8 years: osteotomy preferred, recurrence 15-20%; guided growth is an option with significant growth remaining and moderate deformity. Age 5 is the critical transition - recurrence risk falls sharply beyond it
• Age 8-12 years: osteotomy or guided growth by severity and growth remaining, recurrence under 10%; the adolescent form typically presents here
• Adolescent, 12 years and over: acute osteotomy, since little growth remains; recurrence under 10%, accurate correction is essential, and a Stage VI bar may need resection

OsteotomyGuided GrowthOther Procedures

The proximal tibial valgus osteotomy is the workhorse for established deformity. It is indicated for Stage III-V disease, for angular deformity beyond 15-20 degrees of varus, and for the child over 4 years or after failed bracing - and it can be performed at any age.

The cut. Proximal tibial metaphyseal, distal to the physis, in one of three configurations:

• Opening wedge (medial) - gradual correction and adds length; needs bone graft, and the peroneal nerve is at risk
• Closing wedge (lateral) - inherently stable; shortens the limb and threatens the lateral structures
• Dome - multiplanar, so rotation and procurvatum can be corrected at the same time

Finishing the job. Fix with a plate and screws or an external fixator, and correct to 5-10 degrees of valgus, deliberately past neutral. A fibular osteotomy is often required for a closing wedge or a large correction, and is safer for the peroneal nerve at mid-shaft. Correct the internal tibial torsion at the same sitting, typically 10-20 degrees of external de-rotation. Recurrence tracks the physeal growth remaining, and overcorrection into valgus reduces it.

Guided growth (tension band plating, the 8-plate) restrains the lateral physis and lets the medial side catch up. A tension band plate is placed on the lateral proximal tibia, and on the distal femur too if there is a femoral contribution; valgus accumulates gradually over 12-24 months and the plate is removed once the correction is achieved.

Who it suits. Early disease at Stage II-III with an open physis, at least 2-3 years of growth remaining, age typically 5-10 years, and moderate deformity of 10-20 degrees of varus.

The trade. It is minimally invasive, physiologic and reversible if the limb overcorrects, and it needs no bone graft. Against that it is slow, often 6-12 months or more, it demands growth remaining, it can rebound after removal, it may need bracing afterwards, and it is less predictable than an osteotomy. Complication and failure rates are higher in pathologic physes - Blount disease and the dysplasias - and in obese and adolescent patients. Success is approximately 60-80% in carefully selected patients, best in younger children with moderate deformity.

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Lateral (permanent) hemiepiphysiodesis arrests the lateral physis permanently and lets the medial side correct the varus. It is simple and definitive, but it cannot be reversed, it needs at least 1-2 years of growth remaining, and it risks overcorrection.

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Physeal bar resection is for Langenskiöld Stage VI with a bar involving less than 50% of the physis and at least 2 years of growth remaining. MRI or CT define the bar; it is excised and the defect interposed with fat or Cranioplast to prevent reformation, often combined with an osteotomy. Small peripheral bars do better than large central ones.

Gradual correction with a circular external fixator (Ilizarov or Taylor Spatial Frame) is for severe complex multiplanar deformity, for the very young child in whom acute correction recurs, for recurrent deformity, and where there is a concurrent leg length discrepancy. It corrects angulation, rotation, translation and length at once and can be adjusted during treatment. The costs are pin-site infection, family burden and 3-6 months in a frame. In severe disease with medial plateau depression, fixator-assisted medial plateau elevation combined with lateral epiphysiodesis and a proximal tibial osteotomy can restore joint congruence.

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Acute lengthening with deformity correction is reserved for a significant leg length discrepancy, over 3-4cm, alongside angular deformity, typically close to skeletal maturity, using an intramedullary lengthening nail or an external fixator.

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Proximal tibial osteotomy

Indications

Stage IV+, failed bracing, any age

Advantages

Predictable, immediate correction, definitive

Disadvantages

Recurrence risk if young, peroneal nerve risk

Typical age

4+ years

Guided growth (8-plate)

Indications

Stage II-III, 2+ years growth, moderate deformity

Advantages

Minimally invasive, gradual, reversible

Disadvantages

Slow (12+ months), unpredictable, rebound risk

Typical age

5-10 years

External fixator (Ilizarov/TSF)

Indications

Severe/complex deformity, very young, recurrent

Advantages

Multiplanar correction, adjustable, can lengthen

Disadvantages

Pin sites, prolonged, patient burden

Typical age

Any (especially under 4 or complex cases)

Physeal bar resection

Indications

Stage VI, bar under 50% physis, 2+ years growth

Advantages

Preserves growth potential

Disadvantages

Unpredictable, often needs concurrent osteotomy

Typical age

Variable (depends on bar and growth remaining)

Surgical Options Comparison

Option	Indications	Advantages	Disadvantages	Typical age
Proximal tibial osteotomy	Stage IV+, failed bracing, any age	Predictable, immediate correction, definitive	Recurrence risk if young, peroneal nerve risk	4+ years
Guided growth (8-plate)	Stage II-III, 2+ years growth, moderate deformity	Minimally invasive, gradual, reversible	Slow (12+ months), unpredictable, rebound risk	5-10 years
External fixator (Ilizarov/TSF)	Severe/complex deformity, very young, recurrent	Multiplanar correction, adjustable, can lengthen	Pin sites, prolonged, patient burden	Any (especially under 4 or complex cases)
Physeal bar resection	Stage VI, bar under 50% physis, 2+ years growth	Preserves growth potential	Unpredictable, often needs concurrent osteotomy	Variable (depends on bar and growth remaining)

In recovery. Examine the peroneal nerve and document it - dorsiflexion, first web space sensation, pulses - then multimodal analgesia, ice and elevation. Confirm on the immediate radiographs that the alignment sits at 5-10 degrees of valgus and that the hardware is where it should be.

Immobilisation and weight-bearing. A long leg cast or hinged knee brace for about 6 weeks. Non-weight-bearing for 2-4 weeks if an opening wedge was grafted, then partial and full weight-bearing by 6-8 weeks once union is confirmed.

Follow-up.

• Week 2: wound check and suture removal
• Week 6: clinical and radiographic review, cast off if union is evident, gentle range of motion and progressive weight-bearing
• Month 3: confirm union and alignment; return to sport is typically at 3-4 months
• Month 6, 12, then annually until skeletal maturity: watch for recurrence, especially after early surgery, measuring the MDA and looking for a physeal bar and leg length discrepancy

After guided growth or a frame. Radiographs every 3-4 months after plating, removal once corrected at 12-24 months, then 6-12 months of watching for rebound. A frame needs scheduled adjustments, daily pin-site care and vigilance for pin-site infection, and comes off at consolidation.

Rehabilitation runs through protection for the first 6 weeks, early mobilisation from 6 to 12 weeks, strengthening from 3 to 6 months and return to activity beyond 6 months, with gait re-education for any residual lateral thrust.

Infantile disease treated in time does well. Around 85-90% of appropriately treated children have satisfactory alignment at maturity, and long-term function is excellent, with a low risk of osteoarthritis where the alignment is corrected before a persistent lateral thrust develops.

Adolescent disease is a harder proposition. Surgery achieves satisfactory short-term alignment in the same 85-90%, and recurrence is lower because little growth is left to undo it, but these patients carry a higher rate of early osteoarthritis from the overload that preceded correction. Obesity management is critical to the long-term result, and bracing has nothing to offer them.

What decides the outcome: age at treatment, the Langenskiöld stage together with the slope morphology, obesity, compliance, and laterality - bilateral infantile disease often responds better to bracing.

Global epidemiology:

• Prevalence varies markedly by population - higher in those of African, Afro-Caribbean and Hispanic descent and in regions where infants walk early
• Relatively rare in Northern European/Caucasian populations
• Rising worldwide with childhood obesity, particularly the adolescent (late-onset) form; obesity is an independent, modifiable risk factor for needing surgery

Side-by-side principles (consistent across major bodies):

• There is no single dominant national guideline for Blount disease; practice is driven by classic and contemporary evidence (Levine & Drennan; Feldman & Schoenecker; Stevens; LaMont) and instructional reviews (e.g. POSNA/JPO updates)
• Diagnosis: standing AP radiograph with the Drennan MDA is the universally accepted screening/diagnostic tool; MRI is favoured (over CT) for physeal/bar assessment in children to limit radiation
• Conservative care: KAFO bracing for infantile Stage I-II under age 3 is widely offered, though its efficacy remains debated and is not universally adopted
• Surgery: proximal tibial valgus osteotomy is the global workhorse; growth modulation (tension band plating) and circular external fixators (Ilizarov, Taylor Spatial Frame) are established alternatives where expertise and implants are available

Registry note: Blount disease is a paediatric deformity condition and is not tracked by arthroplasty/implant registries (NJR, AJRR, AOANJRR, SHAR, NZJR). Evidence derives from single-centre and multicentre paediatric series rather than registry data.

High- vs limited-resource variation:

• In well-resourced settings, early screening, MRI, guided growth, and computer-assisted hexapod fixators are available, enabling earlier and less invasive correction
• In limited-resource or remote settings, late presentation with severe (Stage IV-VI) deformity is more common; treatment relies on osteotomy with simple internal or external fixation, and weight-management/lifestyle programmes may be less accessible
• Culturally appropriate counselling, family involvement, and interpreter support improve adherence to bracing and follow-up in all settings

Four decisions in Blount disease are genuinely unsettled. Saying so, and saying why, is a stronger viva answer than asserting a protocol - each of these rests on small single-centre series rather than comparative trials.

The following topics are frequently tested in Orthopaedic exams related to Blount disease:

Blount disease (tibia vara) is a pathologic growth disturbance of the medial proximal tibial physis producing progressive genu varum. Two distinct forms exist: infantile (onset under 4 years, often bilateral) and adolescent (onset after 8 years, obesity-related, usually unilateral).

Key diagnostic features:

• Drennan's metaphyseal-diaphyseal angle (MDA): over 16 degrees diagnostic; 11-16 degrees a gray zone
• Langenskiöld classification (Stages I-VI): Stage IV is the threshold for surgery

Management:

• Observation: physiologic genu varum with MDA under 11 degrees
• Bracing (KAFO): age under 3 years, Stage I-II, MDA 11-16 degrees, 23 hours daily for 12-24 months (60-80% success)
• Surgery: Stage IV or higher, failed bracing, age over 4 years, all adolescent disease
• Options: proximal tibial valgus osteotomy (workhorse; correct to 5-10 degrees valgus); guided growth for selected early cases; external fixator for severe/complex or very young

Critical exam points: differentiate from physiologic bowing using MDA and age; Stage IV = surgery mandatory; overcorrect to 5-10 degrees valgus; address internal tibial torsion (60-80%); and counsel about recurrence when operating on young children. Long-term monitoring until skeletal maturity is essential, particularly after early surgery.