Blount disease, also known as tibia vara, is an acquired disorder affecting the medial proximal tibial growth plates (metaphysis) which results in a multidimensional lower extremity deformity most prominently defined by tibial varus.1
While the exact etiology of Blount disease is unknown, it is postulated to be caused by a combination of factors including hereditary, biomechanical, and possibly metabolic that alter endochondral ossification.1,2
Epidemiology including risk factors and primary prevention
Early walking and obesity are well documented risk factors.1 Familial occurrence has been reported to be between 9-43%.3 Incidence is higher in Scandinavia, Hispanic and African children.3 There has been association with deficiencies in vitamin D, zinc, and alkaline phosphatase.3 Increased mechanical pressure on knee joint such as early walking and obesity have been associated especially with early onset disease.3 However, Blount disease has high prevalence in South Africa where obesity is not common.3 Although several risk factors have been identified, there is no clear evidence on prevention of Blount disease. Generally, Blount disease is classified as early onset (infantile) for patients < 4 years old or later onset for patients >4 years old. 1,2 Early-onset (also known as infantile) is more commonly bilateral, affects females more than males, and is generally more severe. Late-onset is more commonly unilateral.
Blount disease affects the medial proximal tibial growth plate and has other associated findings based on the onset of disease.1 It is thought that repetitive compressive forces may cause growth inhibition leading to deformity.4 In early-onset disease the ossification centers are still pliable and cartilaginous whereas in late-onset the effect is modulated by growth spurts.4,5 While the varus deformity is the most prominent clinical feature, the deformity is multi-dimensional and other changes may include tibial procurvatum (anterior bowing) and internal tibial torsion.1 Femoral involvement is more commonly found in late-onset Blount in the form of a distal femoral varus deformity.6 Weight bearing is thought to be necessary for development of Blount disease since it is not seen in non-ambulatory patients.1
Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)
Normally, the tibiofemoral angle progresses from varus to valgus between 1.5 and 3 years.1 An early indicator of Blount disease is a metaphyseal-diaphyseal angle more than 11 degrees.1 Blount disease is staged by the Langenskiold classification system which follows the natural course of the disease by radiographic characterization of epiphysis, physis, and metaphysis until ultimate closure which leads to significant deformity.7 The classification system is categorized in 6 stages with I being the mildest and VI being the most severe. Without intervention or spontaneous recovery, progression to the later Langenskiold stages can result in pain, arthritis, and significant leg length discrepancies.1
Specific secondary or associated conditions and complications
Given the strong association between obesity and Blount disease, it is important to screen for other obesity related conditions that may affect that patient’s treatment.2 A common example is obstructive sleep apnea which should be screened for prior to general anesthesia for operative management. Other secondary musculoskeletal issues include distal femoral varus/valgus, limb length discrepancy, distal tibia valgus, and medial plateau depression.8
Essentials of Assessment
A comprehensive history is important to help rule out other diagnoses that could mimic Blount disease. This includes but is not limited to any history of trauma, infection (joint or skin), or fractures. History should also include family history, diet, and development.
For assessment of Blount disease, it is important to examine strength (via manual muscle testing if possible), joint range of motion and stability, muscular tone, as well as measure limb length. A special test that may help distinguish genu varum from Blount is the Cover Up test which involves laying the patient supine with patellae forward and covering the proximal thigh and distal leg to assess the alignment of the lateral knee. A neutral or varus alignment is considered a positive test which could indicate early-onset Blount. A valgus alignment is considered a negative test and associated with physiologic knee bowing.9
Blount disease can also sometimes affect gait in a recognizable pattern. Varus thrust gait is defined as accentuation of varus malalignment and lateral knee translation during stance phase that partially corrects in swing. This gait pattern is a clinical entity which can be used for surgical planning.10
As there is some evidence to suggest an association between vitamin D deficiency and Blount disease, checking 25-hydroxyvitamin D level may be helpful. However, there are no strong guidelines on lab studies.
The first line radiographic imaging for diagnosing Blount disease is a standard AP x-ray of the lower extremity. The AP view is helpful for Langenskiold classification as well as identification of other useful measurements for treatment planning and outcome assessment. Tibiofemoral angle is considered to be the most functional measurement of the deformity.1 In early onset Blount, the tibial metaphyseal diaphyseal angle (also known as Drennan’s angle or MDA) can be helpful in diagnosing Blount’s vs. physiologic genu varum. It is generally agreed that an MDA ≤ 9° is more likely physiologic than early-onset Blount’s while the angle diagnostic of Blount’s is debated.11
Supplemental assessment tools
While physical exam and standard x-ray are the mainstays of assessment of Blount’s disease, there may be some use in additional imaging modalities such as CT and MRI. CT may be helpful for better assessment of rotational deformities. MRI may be helpful in evaluating some associated soft tissue changes that have recently been described in patients with Blount disease to include thickened or presence of abnormal signal in the medial menisci, though clinical significance has not been established.2
Early predictions of outcomes
With the limited data available, it is generally understood that early-onset Blount disease tends to lead to more severe deformity. With regards to classification, earlier stage (Langenskiold I – II) tends to respond better to treatment than later stage disease.12
Obesity has the strongest correlation of any factor with regards to Blount disease. Weight management has been studied in relation to Blount disease, but no effective methods have been found in clinical research.13
Social role and social support system
Parents and caregivers play a significant role in the surgical planning phase of treatment. Some surgical interventions (including guided growth and gradual osteotomy) require patients who will not be lost to follow up and have the ability to care for devices (such as an external fixator) and can be important factors in determining treatment course.
Surgical management is a mainstay of treatment in Blount disease, however surgical interventions like ‘guided growth’ are contraindicated in physiologic genu varum underlying the importance of making an accurate diagnosis. There is also no current consensus regarding the amount of ideal correction which is something families should be educated about.
Rehabilitation Management and Treatments
Available or current treatment guidelines
While there are no exact consensus guidelines on the current treatment of Blount disease, there are general tenets that guide treatment based on age of onset, severity, and radiographic/physical exam findings. For Early-onset Blount, treatment can include observation (spontaneous recovery has been reported ),14 bracing, and surgical management. For Late-onset Blount, surgical management is the only option. The goal of treatment, regardless of the method, is to correct the deformity, avoid more invasive treatments, and to prevent recurrence or worsening of the deformity.
At different disease stages
In early-onset Blount, although observation is an option, the two mainstays of treatment are bracing and surgical intervention. Better outcomes with bracing are seen in unilateral disease, Langenskiold stages I or II, and under three years old. Bracing typically involves KAFO that is worn during the day and/or night time that creates a fulcrum with a valgus force at the knee using a three point pressure system either fixed in extension or a free knee joint using valgus straps.15,16 Other studies indicates rotational straps, and five point pressure system also can be helpful.17 There are multiple options regarding surgical intervention for early-onset Blount’s disease, but more recently guided growth has become more widely used. Hemiepiphysiodesis achieves angular correction by means of either permanent or reversible manipulation of the growth plate. This procedure is directed at the lateral aspect of the tibial physis to allow for ‘catch up’ growth on the affected side to reduce deformity.4 Late-onset Blount’s disease is managed with surgical intervention. The most common surgical treatment is tibial osteotomy. This can be accomplished either acutely or gradually. Acute correction provides fastest results but there are concerns for nerve injury and accurate prediction of future growth. The gradual approach requires placement of an external fixator which requires a prolonged healing phase and pin site care/stabilization but with the benefit of being able to adjust during recovery to prevent over/under correction.18
Coordination of care
From the physiatric perspective, a multi-disciplinary approach with orthopedics and orthotists would be preferred for management to determine if patients are appropriate for bracing/conservative care as well as determining when and what surgical intervention may be needed for treatment.
Patient & family education
Families should be educated about the progressive nature of Blount disease and the potential complications of not treating the deformity. Patients and family should also be educated that repair of the deformity does not automatically lead to increased activity and weight loss when obesity is a concern.19
Measurement of Treatment Outcomes
Outcomes data related to Blount disease are historically limited to quantitative measures including MDA, Langenskiold classification, and leg length discrepancy. Outcomes may also include need for repeat surgical intervention or progression/recurrence of deformity. There have been very few studies conducted that use functional or qualitative data for outcome measures.
Translation into Practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills
While genu varum is a known normal variant of childhood development, it is important as physiatrists to closely evaluate patients referred for this reason as the pathology of Blount disease can very closely mimic physiologic bowing but require more invasive management if not treated on early in the disease course. Patients with genu varum should be closely followed and if any progression of deformity is noted (especially after 16-18 months old), radiographic images should be obtained and further diagnostic work up should be considered.4
Cutting Edge/ Emerging and Unique Concepts and Practice
There have been multiple advances in the surgical management of Blount disease. While tibial osteotomy is the historic ‘gold standard’ of treatment, there has been growing research into other surgical options. This includes guided growth, physeal bar resection, and medial tibial plateau elevation. Baraka et. al recently published a prospective study using a new surgical technique involving four stages – epiphysiodesis, fibular osteotomy, tibial medial plateau elevation, and tibial metaphyseal osteotomy with internal fixation for management of severe (Langenskiold V and VI) early-onset Blount disease. This case series showed positive outcomes with both quantitative and qualitative data.10
Gaps in the Evidence-Based Knowledge
The guidance for management of Blount disease comes from a limited case series of prospective or retrospective data. There is a lack of case-control studies, lack of randomized control trials, and lack of functional outcomes. In almost all areas, there is need for more research regarding Blount disease.
- Sheffer B. Osteochondrosis or Epiphysitis and Other Miscellaneous Affections. Fourteenth. Elsevier Inc.; 2013. doi:10.1016/b978-0-323-07243-4.00032-3
- Sabharwal S. Blount disease: an update. Orthop Clin North Am. 2015;46(1):37-47. doi:10.1016/j.ocl.2014.09.002
- Banwarie RR, Hollman F, Meijs N, et al. Insight into the possible aetiologies of Blount’s disease: a systematic review of the literature. J Pediatr Orthop B. 2020;29(4):323-336. doi:10.1097/BPB.0000000000000677
- Robbins CA. Deformity Reconstruction Surgery for Blount’s Disease. Child (Basel, Switzerland). 2021;8(7). doi:10.3390/children8070566
- Wenger DR, Mickelson M, Maynard JA. The evolution and histopathology of adolescent tibia vara. J Pediatr Orthop. 1984;4(1):78-88. doi:10.1097/01241398-198401000-00016
- Myers TG, Fishman MK, McCarthy JJ, Davidson RS, Gaughan J. Incidence of distal femoral and distal tibial deformities in infantile and adolescent blount disease. J Pediatr Orthop. 2005;25(2):215-218. doi:10.1097/01.bpo.0000149858.04659.d8
- Langenskiöld A. Tibia vara: osteochondrosis deformans tibiae. Blount’s disease. Clin Orthop Relat Res. 1981;(158):77-82.
- Khanfour AA. Blount’s disease – an up-to-date insight with contemporary treatment guidelines deduced from critical analysis of a large 146 surgical case series. J Pediatr Orthop B. 2021;30(3):239-249. doi:10.1097/BPB.0000000000000769
- Davids JR, Blackhurst DW, Allen BLJ. Clinical evaluation of bowed legs in children. J Pediatr Orthop B. 2000;9(4):278-284. doi:10.1097/01202412-200010000-00012
- Baraka MM, Hefny HM, Mahran MA, Fayyad TA, Abdelazim H, Nabil A. Single-stage medial plateau elevation and metaphyseal osteotomies in advanced-stage Blount’s disease: a new technique. J Child Orthop. 2021;15(1):12-23. doi:10.1302/1863-2548.15.200157
- Feldman MD, Schoenecker PL. Use of the metaphyseal-diaphyseal angle in the evaluation of bowed legs. J Bone Joint Surg Am. 1993;75(11):1602-1609. doi:10.2106/00004623-199311000-00004
- Winell JJ, Baldwin KD, Wells L. Torsional and Angular Deformities of the Limb. Twenty-Fir. Elsevier Inc. doi:10.1016/B978-0-323-52950-1.00695-7
- Pace G, Hennrikus W. Weight Loss Programs Fail in Obese Patients with Blount's Disease and Slipped Capital Femoral Epiphysis. Pediatrics. 2017;140(1 MeetingAbstract):117 LP – 117. doi:10.1542/peds.140.1_MeetingAbstract.117
- Laville J-M, Wiart Y, Salmeron F. Can Blount’s disease heal spontaneously? Orthop Traumatol Surg Res. 2010;96(5):531-535. doi:10.1016/j.otsr.2010.03.015
- de Miranda Luzo MC, Montenegro NB, Massa BSF, de Angeli LRA, Cordeiro FG, Guarniero R. MANAGEMENT OF INFANTILE BLOUNT’S DISEASE WITH MOLDED ORTHOSES: A NEW PERSPECTIVE. Acta Ortop Bras. 2016;24(2):85-89. doi:10.1590/1413-785220162402153725
- Sabharwal S, Sabharwal S. Treatment of Infantile Blount Disease: An Update. J Pediatr Orthop. 2017;37. https://journals.lww.com/pedorthopaedics/Fulltext/2017/09001/Treatment_of_Infantile_Blount_Disease__An_Update.7.aspx
- Alsancak S, Guner S, Kinik H. Orthotic variations in the management of infantile tibia vara and the results of treatment. Prosthet Orthot Int. 2013;37(5):375-383. doi:10.1177/0309364612471369
- Griswold BG, Shaw KA, Houston H, Bertrand S, Cearley D. Guided growth for the Treatment of Infantile Blount’s disease: Is it a viable option? J Orthop. 2020;20:41-45. doi:10.1016/j.jor.2020.01.007
- Sabharwal S, Zhao C, Sakamoto SM, McClemens E. Do children with Blount disease have lower body mass index after lower limb realignment? J Pediatr Orthop. 2014;34(2):213-218. doi:10.1097/BPO.0b013e3182a11d59
Mi Ran Shin, MD
Nothing to Disclose
Nicole Eno, MD
Nothing to Disclose
Katherine DeGraaff, MD
Nothing to Disclose
Justin Burton, MD
Nothing to Disclose