Blount disease

Blount disease, also known as tibia vara or Blount-Barber syndrome, is a developmental disorder affecting the growth plates (physes) of the proximal tibia (shinbone), leading to progressive bowing of the legs (genu varum). The condition results from abnormal endochondral ossification of the medial portion of the proximal tibial physis, causing the inner part of the tibia to develop abnormally while the outer part continues to grow normally. This asymmetric growth leads to progressive angular deformity of the lower limbs. The skeletal system is primarily affected, with the hallmark feature being progressive bowleg deformity that worsens over time if untreated. Blount disease is classified into two main forms based on age of onset: the infantile (early-onset) form, which typically presents between ages 1 and 3 years, and the adolescent (late-onset) form, which manifests around age 10 or later. The infantile form is more common and is frequently bilateral, while the adolescent form tends to be unilateral. Key clinical features include progressive bowing of the legs, a prominent medial tibial metaphyseal beak visible on radiographs, internal tibial torsion, lateral thrust during walking, limb-length discrepancy, and potential knee joint instability. Obesity and early walking are recognized risk factors, particularly for the infantile form. The condition is more prevalent in certain populations, including individuals of African descent. Treatment depends on the severity and age of the patient. In early stages of the infantile form, bracing (such as a knee-ankle-foot orthosis) may be effective if initiated before age 3. When conservative measures fail or the disease is diagnosed later, surgical intervention is typically required. Surgical options include proximal tibial osteotomy (cutting and realigning the bone), guided growth procedures using hemiepiphysiodesis (placing a plate on one side of the growth plate to redirect growth), and in severe cases, external fixation with gradual correction. Early diagnosis and intervention are important to prevent progressive deformity and secondary complications such as arthritis of the knee joint.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

Common questions about Blount disease