Blount's Disease

Synonyms: Tibia vara

Blount's disease is a disorder of the tibial growth plate (usually medial aspect) leading to changes in the angle at the knee. This results in bowing of the leg (usually lower leg). However, unlike bowlegs it is pathological and progressively worsens. Clinically it is difficult to distinguish between simple bowlegs and Blount's disease. However, bowlegs should resolve between the ages of 2-4 years - if not then one should suspect Blount's disease.¹

Epidemiology

Presents at age 2-4 years

Risk factors

Repetitive trauma to a knee with an already varus abnormality

Presentation

• Usually bilateral
• Bony prominence over the medial tibial condyle (non-tender)³
• Feet held in pronation
• Shortening of the involved leg
• Medial angulation and internal rotation of proximal tibia
• Gait - painless varus thrust seen

Investigations

Plain radiographs show increased angulation between the metaphysis and the longitudinal axis of the tibia.

• Physiologic bow legs
• Rickets
• Osteomyelitis
• Trauma
• Ollier's disease
• Metaphyseal chondrodysplasia
• Focal fibrocartilaginous dysplasia

Management

• Braces - these are long-legged and lock the knee and need to be worn whilst weight bearing.
• However, if by the age of 4-5 years the condition has not corrected then surgery is usually required.
• Surgery usually involves osteotomy of the tibia and realignment of the lower leg.

Prognosis

• Bracing is usually unsuccessful in girls and those with obesity.
• If treatment is successful there is usually no residual disability or cosmetic abnormality.⁴

Usually the adolescent variety is less severe than infantile Blount's disease.

Risk factors

• Bowlegs
• Females
• Afro-caribbean ethnicity
• Obesity
• Walking at early age
• Possible family preponderance

Presentation

• Commonly unilateral
• Varus deformity
• Shortening of involved leg up to 3-4 cm
• Pain at the medial prominence of the proximal tibia
• Medial tibial torsion may also be present

Investigations

Plain radiographs as for infantile Blount's.

Treatment

High tibial osteotomy is usually the procedure of choice. This is attractive as limbs are not shortened however it requires the wearing of an external fixator for several months.