Professional Reference articles are designed for health professionals to use. They are written by UK doctors and based on research evidence, UK and European Guidelines. You may find one of our health articles more useful.
Treatment of almost all medical conditions has been affected by the COVID-19 pandemic. NICE has issued rapid update guidelines in relation to many of these. This guidance is changing frequently. Please visit https://www.nice.org.uk/covid-19 to see if there is temporary guidance issued by NICE in relation to the management of this condition, which may vary from the information given below.
Synonyms: tibia vara
What is Blount's Disease?
Blount disease is an asymmetrical disorder of proximal tibial growth that produces a three-dimensional deformity. Tibia vara (also known as genu varus and bow-leggedness) is the main component of the deformity.
Blount disease exists as two clinical variants, early-onset, and late-onset. Late-onset Blount's disease can be divided into juvenile tibia vara (ages 4-10), and adolescent tibia vara (ages 11 and older).
Blount's disease is caused by disorder of the tibial growth plate (usually the medial aspect) leading to changes in the angle at the knee. This results in bowing of the leg (usually the lower leg). However, unlike bow legs it is pathological and progressively worsens.
Clinically it is difficult to distinguish between simple bowlegs and Blount's disease. However, bow legs are normal in children aged under 2 years.
Early diagnosis and early treatment are essential.
Early-onset Blount's disease
Presents at age 2-4 years.
Repetitive trauma to a knee with an already varus abnormality.
- Usually bilateral.
- Bony prominence over the medial tibial condyle (nontender).
- Feet held in pronation.
- Shortening of the involved leg.
- Medial angulation and internal rotation of the proximal tibia.
- Gait - painless varus thrust seen.
Plain radiographs show increased angulation between the metaphysis and the longitudinal axis of the tibia.
- Physiological bow legs.
- Ollier's disease.
- Metaphyseal chondrodysplasia.
- Focal fibrocartilaginous dysplasia.
Late-onset Blount's disease
- Bow legs.
- Afro-Caribbean ethnicity.
- Walking at an early age.
- Possible family preponderance.
- Commonly unilateral.
- Varus deformity.
- Shortening of the involved leg by up to 3-4 cm.
- Pain at the medial prominence of the proximal tibia.
- Medial tibial torsion may also be present.
Plain radiographs, as for infantile Blount's disease.
Surgical options depend on the patient's age, weight, extent of physeal involvement, severity, and number of deformities.
Before 4 years of age, progressive Blount disease should be corrected, preferably by a simple osteotomy. Once medial tibial epiphysiodesis has developed, both a complementary epiphysiodesis and gradual external fixator correction of the other alignment abnormalities, rotational deformity, and limb length are required.
Otherwise options include growth modulation procedures such as guided growth for gradual correction with hemi-epiphysiodesis and physeal closure to prevent recurrence and equalise limb lengths, physeal bar resection, physeal distraction, osteotomies with acute correction and stabilisation, gradual correction with multi-planar dynamic external fixation, and various combinations of all modalities.
The goals of surgery are to restore normal joint and limb alignment, equalise limb lengths at skeletal maturity, and prevent recurrence.
Untreated Blount disease is associated with a poor prognosis, especially in young children due to the growth spurt and the early fusion of the growth plate occurring from the ages of 6 to 8.
Early-onset Blount's disease progresses to more severe deformities, including depression of the medial tibial plateau. Additional deformities in both groups include proximal tibial procurvatum, internal tibial torsion, and limb length discrepancy. Compensatory deformities in the distal femur and distal tibia may occur.
Untreated Blount disease in adults is rarely encountered. A more common occurrence is the presence of residual abnormalities at skeletal maturity in patients treated for Blount disease in childhood.
Premature osteoarthritis may develop.
Further reading and references
Murthy D, De Leucio A; Blount Disease. StatPearls, July 2022.
Janoyer M; Blount disease. Orthop Traumatol Surg Res. 2019 Feb105(1S):S111-S121. doi: 10.1016/j.otsr.2018.01.009. Epub 2018 Feb 23.
Robbins CA; Deformity Reconstruction Surgery for Blount's Disease. Children (Basel). 2021 Jun 308(7):566. doi: 10.3390/children8070566.
Infantile Blount's disease; Paediatric Genu Varum Wheeless' Textbook of Orthopaedics
Delniotis I, Leidinger B, Kyriakou A, et al; Blount's disease: The importance of early diagnosis and early treatment. Clin Case Rep. 2019 May 207(7):1454-1455. doi: 10.1002/ccr3.2214. eCollection 2019 Jul.
S.R. Boyea and J.R.Bowen; Clinical case presentation on Blount's disease June 1996.
Chkili S, Simoni P; Blount Disease. J Belg Soc Radiol. 2021 Sep 23105(1):51. doi: 10.5334/jbsr.2557. eCollection 2021.