Growth

Knock-knees and Bow legs: Crooked Legs in Children

Knock knees or bow legs are a normal part of growth at certain ages. What matters is age, symmetry, progression and residual growth.

Updated: September 2026·Medically reviewed by Dr. Daniele Priano

Quick Answers

Is it normal for a child to have crooked legs?
Yes, angular deviations of the knee are normal during growth. Bow legs are typical in the first years of life, while knock-knees are common in preschool and school age. Most cases resolve spontaneously.
When should I worry about knock-knees?
An evaluation is advised if the valgus appears markedly increased, asymmetric between the two limbs, worsening rather than improving with growth, or if it causes pain, fatigue or gait difficulty. Intercondylar and intermalleolar distances measured at home are only orientative: they vary with foot position, limb rotation and measurement technique, and on their own are neither a diagnosis nor an automatic threshold for tests or surgery. What matters most is how it evolves over time, any asymmetry, the clinical examination and, when indicated, a weight-bearing X-ray.
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Front view comparison: bow legs on the left, with knees apart, and knock knees on the right, with knees close together.

Two different shapes

Bow legs are shown on the left: the knees are apart with the ankles close together. Knock knees are on the right: the knees are close with the ankles apart. The illustration explains the difference; it cannot measure or diagnose a deformity.

Read all the illustrated explanations →

Crooked legs — knock-knees (genu valgum) and bow legs (genu varum) — are part of the normal evolution of lower limb alignment during growth. In the first years of life a varus appearance typically prevails, gradually giving way to a valgus phase in preschool and school age, until final alignment is reached in later childhood.

In the great majority of cases this is a physiological, self-limiting picture that changes spontaneously with bone growth, without the need for corrective devices, insoles or braces. A markedly increased deviation, asymmetry between the two limbs or progressive worsening is, however, a signal that deserves a clinical evaluation.

During the visit we observe posture, gait and limb axis, ruling out secondary causes (nutritional deficiencies, bone disorders, post-traumatic changes) and agreeing with the family on an appropriate observation plan. The same deviation can be entirely physiological at one age and deserve further evaluation at another: what makes the difference is age, symmetry, how it evolves over time, the site of the deformity and the residual growth available.

This page answers the question "is it physiological in my child?". When the evaluation does confirm an indication for treatment, the useful window to exploit residual growth is not unlimited: for this reason, in doubtful or marked cases, it is best not to delay the evaluation. Only in selected situations, of marked degree or with significant evolutive potential, is a targeted correction considered, described on the dedicated surgical page.

Dott. Daniele Priano - Ortopedico Pediatrico

🦵Children's Legs Change

Knock knees ('X-shaped') are physiological between ages 3-7, just as bow legs ('O-shaped') are normal in the first 2 years. These are developmental patterns that correct spontaneously in most cases. I evaluate if it's within normal range for age or requires further investigation.

Assessment and treatment

When to seek evaluation

  • Varus that remains marked beyond 2-3 years or does not improve
  • Marked valgus or valgus persisting beyond 8-10 years
  • Significant asymmetry between the two legs
  • Deviation progressively worsening with growth
  • Pain or gait disturbances

What is evaluated

  • Clinical evaluation of knee alignment, relative to age
  • Comparison between the two limbs to detect asymmetries
  • Mechanical axis evaluation of lower limbs
  • Gait and posture examination
  • Weight-bearing lower limb X-rays when indicated
  • Exclusion of pathological forms (rickets, dysplasias)

Treatment options

  • Observation and follow-up in most cases
  • Periodic photographic and clinical monitoring
  • Guided temporary hemiepiphysiodesis (growth modulation) in selected cases
  • Corrective osteotomy in severe forms

Types and Normal Values

🦵Genu Varum (Bow Legs)

The knees are apart while the ankles touch. This is a physiological pattern in the first 1-2 years of life, which tends to progressively reduce. What matters clinically is not an isolated measurement taken at home, but the child's age, the symmetry between the two sides and how it evolves over time: a varus that is marked, asymmetric or does not reduce with growth deserves an evaluation.

Normal Evolution:

0-18 monthsvarus patternPhysiological phase, typical of this period
18-24 monthsprogressive reductionThe alignment tends to approach neutral
> 2-3 yearsalignment settlingIf varus remains marked or is asymmetric, an evaluation is appropriate

🦵Genu Valgum (Knock Knees)

The knees touch while the ankles are apart. This is a physiological pattern between roughly 3 and 6-7 years. Here too, no measurement taken at home can on its own establish whether the picture is normal: what counts is age, symmetry, evolution over time, the site of the deformity and residual growth.

Normal Evolution:

3-4 yearsphysiological peakPhase of maximum expression of valgus, typically physiological
5-7 yearsspontaneous correctionThe alignment tends to progressively reduce
> 8-10 yearsalignment stabilisingA valgus that remains marked, asymmetric or worsens with growth should be evaluated

Frequently Asked Questions

Is it normal for a child to have crooked legs?▼
Yes, angular deviations of the knee are normal during growth. Bow legs are typical in the first years of life, while knock-knees are common in preschool and school age. Most cases resolve spontaneously.
When should I worry about knock-knees?▼
An evaluation is advised if the valgus appears markedly increased, asymmetric between the two limbs, worsening rather than improving with growth, or if it causes pain, fatigue or gait difficulty. Intercondylar and intermalleolar distances measured at home are only orientative: they vary with foot position, limb rotation and measurement technique, and on their own are neither a diagnosis nor an automatic threshold for tests or surgery. What matters most is how it evolves over time, any asymmetry, the clinical examination and, when indicated, a weight-bearing X-ray.
Do braces or special shoes correct crooked legs?▼
No, there is no scientific evidence that braces, orthopaedic shoes or insoles correct physiological knee deviations. Correction occurs naturally with growth. Only in selected pathological cases may a specific orthopaedic plan be indicated.
Are crooked legs hereditary?▼
There is a familial component: children whose parents had a similar alignment may show a more evident or slower-to-correct picture. However, family history alone does not indicate a pathology — clinical evaluation remains the reference point.
My child plays sports: are knock-knees or bow legs a problem?▼
In the vast majority of cases, no. Sports are actually encouraged because they support good muscular and proprioceptive development, useful for limb maturation. In markedly increased or symptomatic forms we discuss possible adjustments together, without forbidding physical activity.
Is there an age by which crooked legs must be corrected?▼
There is no rigid deadline that fits everyone. In general, knee alignment stabilizes in later childhood: if at that point the deviation remains significant or continues to worsen, an in-depth evaluation may be appropriate. Deciding case by case, considering remaining growth and the clinical picture, is the most appropriate approach.
Can the pubertal growth spurt worsen knock-knees?▼
In some children, the pubertal growth spurt can temporarily increase an existing valgus because bone growth accelerates exactly when the growth plate is most reactive. For this reason the pre-pubertal and pubertal windows are useful clinical checkpoints to re-evaluate limb alignment and, when indicated, plan a minimally invasive correction guided by remaining growth — an option that is no longer available once skeletal maturity is reached.
What is a weight-bearing lower limb X-ray for?▼
A weight-bearing lower limb X-ray (taken standing, with the child loading the leg) allows measurement of the true mechanical axis, distinguishing femoral, tibial or combined valgus and ruling out pathological causes (rickets, dysplasia, post-traumatic sequelae). It's a targeted exam, requested only when the clinical evaluation suggests an evolving picture, and is not part of routine screening.
What's the difference between hemiepiphysiodesis and adult corrective surgery?▼
**Temporary hemiepiphysiodesis** (growth modulation with eight-plates) is a minimally invasive pediatric technique: a small plate selectively slows one side of the growth plate and correction occurs gradually, using remaining growth. In straightforward cases early weight-bearing without a cast is often permitted, following the surgeon’s instructions. The plate is removed at the appropriate time and growth is monitored afterwards because deformity may rebound. In adults the growth plate is closed, so an osteotomy (cutting and realigning the bone) is required, with longer and more demanding recovery. That's why, when indicated, acting within the pediatric window is technically advantageous.
How long is follow-up after a diagnosis of genu valgum or varum?▼
Follow-up frequency is not the same for every child. A clearly physiological pattern may not need a fixed orthopaedic schedule, whereas an asymmetric, progressive deformity or one treated with growth modulation needs planned review according to remaining growth and correction rate. The schedule is defined after clinical and, when needed, radiographic assessment.

Important Notice: The information on this page is for educational and informational purposes only and does not constitute medical advice. Each clinical case is unique: the appropriate treatment is determined during the specialist consultation, based on a thorough clinical examination and, where necessary, diagnostic imaging. For any doubts or concerns, please consult a specialist.