Genu Varum

Definition

  • Bowed legs, with knees apart when the ankles touch
  • Most cases in young children are physiological and resolve spontaneously

Anatomy

  • Salenius and Tunnessen described normal tibiofemoral angle development
  • Varus at birth
  • Neutral by 18 to 24 months
  • Physiological valgus peaks at 3 to 4 years
  • Adult mild valgus by about 7 years

Aetiology

  • Infantile and adolescent Blount disease
  • Nutritional or X-linked hypophosphataemic rickets
  • Skeletal dysplasias such as achondroplasia and metaphyseal chondrodysplasia
  • Post-traumatic or post-infective physeal arrest
  • Focal fibrocartilaginous dysplasia

Clinical Features

  • Persistence or worsening beyond 2 years suggests pathology
  • Asymmetry, severe deformity, short stature or dysmorphism
  • Lateral thrust of the knee in gait
  • Family history or dietary risk for rickets

Classification

  • Blount disease affects the posteromedial proximal tibial physis, causing varus, procurvatum and internal tibial torsion
  • Infantile type before 4 years, usually bilateral, linked to early walking, obesity and African descent
  • Adolescent type after about 10 years, more often unilateral, in obese children, may include distal femoral varus
  • Langenskiold six stages, from medial metaphyseal beaking (I) to a medial physeal bony bridge (VI)

Investigations

Angular Tibial Bowing, radiograph of bowed legs in rickets
Radiograph of bowed legs in rickets. Image by The original uploader was Mrich at English Wikipedia., Wikimedia Commons, CC BY-SA 1.0.
  • Standing long leg radiograph when pathology is suspected
  • Drennan metaphyseal-diaphyseal angle, between the metaphyseal beak line and a perpendicular to the tibial shaft
  • Less than 11° likely physiological
  • Greater than 16° strongly associated with Blount disease
  • Rickets bloods are calcium, phosphate, ALP, vitamin D and PTH
  • Rickets radiographs show widened, cupped and frayed physes

Management

  • Physiological bowing, reassurance and observation
  • Rickets, medical treatment first, surgery for residual deformity after metabolic control
  • Infantile Blount stages I to II under 3 years, KAFO
  • Progressive disease, proximal tibial valgus osteotomy with slight overcorrection, ideally before 4 years
  • Later stages may need bar resection, medial plateau elevation and osteotomy
  • Lateral hemiepiphysiodesis for milder disease with growth remaining
  • Adolescent Blount, guided growth or osteotomy, often gradual correction in a circular frame

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.