Genu Valgum (Pediatric)

Synonyms
Knock-knees

INTRODUCTION

Definition

Condition in which the knees angle in and touch each other when the legs are straightened. Might be uni- och bilateral. 

Epidemiology

Bilateral angular deformity is common and is most often physiologic.

Physiology

  • Normal knee alignment progresses from 10-15° of varus at birth to maximal valgus angulation of up to 20° at age of 3-4 years. Genu valgum should not increase after 7 years of age. After age 7 years, valgus should not exceed 12°, and the intermalleolar distance should be less than 8 cm.
  • Neutral femoral-tibial alignment occurs at 12-14 months old.

Pathoanatomy

The deformity is usually localized in the distal femur but it may also arise in the proximal tibia.

Etiology

Bilateral
  • Physiologic genu valgum (most often)
  • Rickets, renal osteodystrophy
  • Skeletal dysplasia: E.g. chondroctodermal dysplasia, spondyloepiphyseal, Morquio syndrome
Unilateral: Bilateral genu valgum often occurs from pathological conditions.
  • Physeal injury (trauma, infection, or vascular)
  • Proximal tibial metaphyseal (Cozen) fracture
  • Benign tumors: E.g. fibrous dysplasia, Ollier disease, osteochondroma

CLINICAL FEATURES

Symptoms

The child usually doesn’t have any symptoms.

DIAGNOSIS

X-ray

Will show the genu valgum. 

TREATMENT

Overview

Pathologic genu valgum should generally be treated with surgery. Patients within this physiologic range do not require treatment.

Nonoperative Treatment

Orthotics/bracing is not effective in genu valgum. If genu valgum occurs after proximal tibial metaphyseal fracture (Cozen phenomenon) it will typically remodel spontaneously and should be observed.

Operative Treatment

Indication: If the mechanical axis falls in the outer quadrant of the tibial plateau (or beyond) in children older than 10 years, i.e. in children older than 10 years with > 10 cm between the medial malleoli or > 15° of valgus angulation. 
  • Mechanical axis is represented by a line drawn from the center of the femoral head to the center of the distal tibial plafond.
Method:
  • Hemiepiphysiodesis or temporary physeal tethering with staples, transphyseal screws, or plate/screw devices of the medial side is effective before the end of growth for severe deformities.
  • Varus-producing osteotomies could be necessary when insufficient growth remains or the site of the deformity is away from the physis. 
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References