Genu Varum (Bowed legs)

By admin On Jan 24, 2024

Ovid: 5-Minute Orthopaedic Consult

Editors: Frassica, Frank J.; Sponseller, Paul D.; Wilckens, John H.

Title: 5-Minute Orthopaedic Consult, 2nd Edition

> Table of Contents > Genu Varum (Bowed legs)

Genu Varum (Bowed legs)

Paul D. Sponseller MD

Basics

Description

The knee goes through normal phases of
changing alignment in childhood: Genu varum (bowed legs) is physiologic
in infants and young children up to 2 years of age, and its appearance
is maximal at 12–18 months of age (1–3).
Bowing is most obvious when children start walking.
It may be combined with internal tibial torsion, which makes it appear more pronounced.
Bowing may seem greater with weightbearing.
This condition usually resolves by 2 years of age and changes to physiologic genu valgum (knock-knee) (2).
Tibia vara (Blount disease) (see “Blount Disease”
chapter), rickets, fibrocartilaginous dysplasia of the proximal tibia,
and other genetic disorders can cause pathologic genu varum (Fig. 1-1).

Epidemiology

Physiologic (normal) bowing is ~1,000 times more common than pathologic bowing (e.g., Blount disease) (1,3).
It occurs equally in boys and girls.

Risk Factors

Family history

Genetics

Some causes of bowed legs are familial:
- Blount disease
- Renal rickets
- Skeletal dysplasia
  
  Fig. 1. Patient with severe untreated infantile varus now in adolescence.

Etiology

Bowing is an imbalance between the load and growth plate development.
It may be caused by:
- Overweight
- Rickets (4)
- Skeletal dysplasia
Physiologic causes: Normal growth
patterns of the femoral and tibial growth plates include a period of
normal varus in early infancy.
Pathologic causes:
- Tibia vara (Blount disease)
- Rickets (nutritional or renal)
- Achondroplasia
- Epiphyseal and metaphyseal dysplasias
- Focal fibrocartilaginous dysplasia
In most of these conditions, the varus results from inability of the growth plate to respond normally to load (3).

Associated Conditions

Early walker
Heavy weight

Diagnosis

Signs and Symptoms

Parental concern about the appearance of the legs is the most common reason for the presentation of children.
The patient should be pain free; if pain exists, another cause should be sought.
Genu varum may develop spontaneously in
the overweight adolescent who previously had straight legs (adolescent
Blount disease), and it usually requires treatment (Fig. 2).

History

If a patient has physiologic bowing, the parents should start to notice improvement after the 2nd birthday (3).

Fig. 2. 13-year-old boy with adolescent genu varum. Note the widened medial physis.

Physical Exam

Obtain a medical, family, and developmental history.
Determine the patient’s height and weight percentiles.
Estimate the angulation of the knee.
Check the rotation of the tibia and femur.
To monitor the patient’s progress, document the distance between the medial surfaces of the knees (intercondylar distance) (5,6).

Tests

Lab

In routine cases, tests are not indicated if varus appears mild and physiologic.
If metabolic causes are suspected, serum
calcium, phosphate, alkaline phosphatase, 1,25-vitamin D, and
creatinine levels may be measured (3,4).

Imaging

Radiographic evaluation of bowed legs in
children <18 months old should be reserved for asymmetric bowing or
for patients suspected of having a pathologic condition other than
benign physiologic varus.
A single AP radiograph of the lower
extremity from hip to ankle on a standing film is the most appropriate
1st imaging study; care should be taken that the knee is pointing
straight ahead.
Widening of physis suggests rickets;
delayed ossification of the distal femoral and proximal tibial
epiphyses may be a result of excessive pressure on 1 side of the knee.
The femorotibial angle and the metaphyseal–diaphyseal angle of the tibia should be measured (5).
If the metaphyseal–diaphyseal angle is <11°, physiologic bowing is assured.
If the metaphyseal-diaphyseal angle is >16°, the child has Blount disease.

If the metaphyseal bowing in the femur is
equal to or greater than that in the tibia, the bowing is more likely
to be physiologic (1) (Fig. 3).

Fig.
3. This 2-year-old patient had bowed legs. The metaphyseal–diaphyseal
angle is 10° on each side. The bowing is more pronounced on the femoral
than the tibial metaphysis. It resolved without treatment.

P.155

Differential Diagnosis

Achondroplasia
Rickets
Infantile or adolescent Blount disease
Metaphyseal or epiphyseal dysplasia

Treatment

General Measures

Physiologic conditions:
- Physiologic bowing always resolves without treatment; bracing is not needed
- At ≥18 months of age, follow-up
  examination and imaging are needed to differentiate physiologic bowing
  from tibia vara (may be difficult) (6).
Pathologic conditions:
- Rickets or other metabolic bone disease:
  - The underlying disease is treated, with osteotomy reserved for those patients with persisting varus after treatment.
- Achondroplasia and epiphyseal or metaphyseal dysplasia:
  - The patient may need surgical treatment, depending on the degree of deformity.
- Tibia vara (Blount disease):
  - Brace treatment is appropriate for children <3 years old; a knee-ankle-foot brace may be used for walking.
  - If the patient is >4 years of age, osteotomy is recommended.

Special Therapy

Physical Therapy

Not necessary for physiologic bowing
Not an effective treatment for pathologic varus

Surgery

Many different types of osteotomy are
available for correcting varus deformity, including dome, oblique,
closing wedge, or opening wedge osteotomy.
The tibia or the femur may require surgery, depending on the site of the deformity.
Physeal bar resection or hemiepiphysiodesis may be indicated for some cases.

Follow-up

Prognosis

Physiologic genu varum has an excellent prognosis for spontaneous improvement.
The prognosis of pathologic genu varum varies.
Knee pain and worsening of the bow are likely in adulthood if the deformity is >10–15° (5).

Complications

Untreated genu varum may cause pain on the medial part of the knee and eventual arthritis during adulthood.
Adolescent genu varum may be painful.
Complications occasionally seen from surgery may include:
- Infection
- Compartment syndrome
- Recurrence of deformity
- Growth disturbance

Patient Monitoring

The frequency of follow-up varies, depending on the individual surgeon or pediatrician.
Physiologic bowing does not need frequent
follow-up unless the condition is not improving; resolution is a slow
process and may take a year.
Pathologic bowing needs more prolonged follow-up.

References

1. Bowen
RE, Dorey FJ, Moseley CF. Relative tibial and femoral varus AS a
predictor of progression of varus deformities of the lower limbs in
young children. J Pediatr Orthop 2002;22:105–111.

2. Salenius P, Vankka E. The development of the tibiofemoral angle in children. J Bone Joint Surg 1975;57A:259–261.

3. Schoenecker PL, Rich MM. The lower extremity. In: Morrissy RT, Weinstein SL, eds. Lovell and Winter’s Pediatric Orthopaedics, 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2006:1157–1211.

4. Biser-Rohrbaugh A, Hadley-Miller N. Vitamin D deficiency in breast-fed toddlers. J Pediatr Orthop 2001;21:508–511.

5. Gordon JE, King DJ, Luhmann SJ, et al. Femoral deformity in tibia vara. J Bone Joint Surg 2006;88A:380–386.

6. Langenskiold A. Tibia vara. A critical review. Clin Orthop Relat Res 1989;246:195–207.

Miscellaneous

Codes

ICD9-CM

736.42 Genu varum

Patient Teaching

Parents should be told that physiologic
genu varum will resolve spontaneously and slowly; if it is not starting
to improve at least by 2–3 years of age, additional evaluation is
needed.
No restriction on activity is recommended.
Exercises do not help genu varum resolve.

FAQ

Q: Do infant “jumper” devices contribute to bowed legs?

A: No evidence suggests that they do. The children are supported in these devices, so the load on the legs is controlled.

Q: When should a child with bowing be referred to a specialist?

A: If the bowing gets worse after 18 months or persists after the 2nd birthday.