UMEM Educational Pearls

Category: Orthopedics

Title: Blount's disease

Keywords: Varus, knee (PubMed Search)

Posted: 5/15/2022 by Brian Corwell, MD (Updated: 6/30/2022)
Click here to contact Brian Corwell, MD

4-year-old patient comes to the ED for an unrelated complaint and you notice that his knees appear to be touching while his ankles remain apart.

 

Genu Varum or “knock knees” may be caused by Infantile Blount’s disease

          -A progressive pathologic condition causing genu varum in children between ages 2 to 5

          - Centered at the tibia

          -Bilateral in up to 80%

          -More common in boys

          -Leg length discrepancy

          - Articular incongruity

Risk factors:  Early walkers (<1 year), overweight, large stature, Hispanic and African American

Results in disruption of normal cartilage growth at the MEDIAL aspect of the proximal tibia while LATERAL growth continues normally

May complain of knee soreness or subjective instability

On physical exam

          Focal angulation of the proximal tibia

Lateral thrust during stance phase of walking (brief lateral shift of proximal fibula and tibia)

          No tenderness or effusion

Imaging:   Plain film shows varus deformity of the proximal tibia with medial beaking (beak like appears of bone) and downward slope of the proximal tibia metaphysis (increased metaphyseal-diaphyseal angle)

 

https://paleyinstitute.org/wp-content/uploads/blounts1.jpg

Treatment depends upon the age of the child and the severity

  1. Medial unloader braces (should be started by age 3)

Successful in up to 80%

  1. Surgical correction (tibial osteotomy or growth plate arrest surgery)

Note: In adolescent variant bracing is ineffective and surgery is only treatment

          : Genu varum is normal in children <2 years old and becomes neutral at 14 months

 

DDX: Physiologic varus, Rickets