Blount’s disease, also known as Blount disease, is a condition affecting the growth plate around the knee, leading to a bowleg deformity. This condition primarily impacts children and is often observed in early walkers and those with obesity. Recognizing and accurately diagnosing Blount’s disease is crucial for effective management and preventing long-term complications. The hallmark symptom of Blount’s disease is pronounced bowlegs, typically appearing by the age of two.
Image alt text: Child exhibiting bowlegs, a key indicator for Blount’s Disease diagnosis, standing to show leg curvature.
In Blount’s disease, the most common site of deformity is the top of the tibia, the larger bone in the lower leg. This occurs because the outer side of the tibia continues to grow normally, while growth on the inner side is stunted. Blount’s disease can affect one or both legs. Without proper diagnosis and intervention, Blount’s disease can worsen, increasing the risk of knee joint arthritis and other degenerative joint issues later in life. Therefore, timely and accurate Blount’s disease diagnosis is paramount.
Image alt text: X-ray image crucial for Blount’s Disease diagnosis, illustrating the bone structure and growth plate abnormalities in a child’s bowlegs.
Figures 1 & 2: Clinical photograph and standing-alignment X-ray demonstrating bowlegs in a child diagnosed with Blount’s disease.
Understanding the Diagnostic Process for Blount’s Disease
The diagnosis of Blount’s disease is a multi-step process that relies on a combination of clinical evaluation and radiographic imaging. A pediatric orthopedist will typically conduct a thorough patient history review, a physical examination, and utilize standing-alignment X-rays to confirm the presence and severity of Blount’s disease.
Patient History and Physical Examination in Blount’s Diagnosis
The initial steps in Blount’s disease diagnosis involve gathering a detailed patient history. This includes information about the child’s age, when the bowlegs were first noticed, developmental milestones like walking age, and any family history of skeletal disorders. Factors such as rapid weight gain and early walking are often considered risk factors.
A physical examination is crucial to assess the degree of bowleg deformity, the range of motion in the knees and hips, and to rule out other potential causes of bowlegs. The orthopedist will observe the child’s gait and posture, paying close attention to the alignment of the legs. While physical examination provides initial clues, it’s the radiographic assessment that confirms the Blount’s disease diagnosis.
The Role of X-rays in Confirming Blount’s Disease Diagnosis
Standing-alignment X-rays are indispensable for a definitive Blount’s disease diagnosis. These specialized X-rays capture an image of the leg from the hip to the ankle while the child is standing. This weight-bearing view is essential because it accurately demonstrates the mechanical axis of the leg deformity and pinpoints the location and severity of the growth plate abnormality characteristic of Blount’s disease.
The pediatric orthopedist analyzes the X-ray to measure angles and assess the growth plate at the proximal tibia (top of the shinbone). Specific radiographic features, such as metaphyseal beaking and epiphyseal-metaphyseal angle, are key indicators for Blount’s disease diagnosis and help differentiate it from physiological bowing, which is common in toddlers and usually resolves on its own. The standing-alignment X-ray is therefore not just for confirmation, but also for staging the severity of Blount’s disease, which guides treatment decisions.
Differential Diagnosis: Distinguishing Blount’s Disease from Other Conditions
An accurate Blount’s disease diagnosis also involves differentiating it from other conditions that can cause bowlegs in children. Physiological bowing, nutritional rickets, and skeletal dysplasias are among the conditions that must be considered in the differential diagnosis.
Ruling Out Physiological Bowing
Physiological bowing is a common and normal variation in leg alignment seen in infants and toddlers. It is typically symmetrical, mild, and resolves spontaneously by the age of 2 or 3 years without any intervention. In contrast, Blount’s disease often presents with more severe bowing, can be asymmetrical, and progressively worsens without treatment. Radiographic evaluation is crucial to differentiate between physiological bowing and early-stage Blount’s disease, especially as clinical appearance alone may be insufficient in the early stages. The persistence of bowing beyond the age of 2, particularly if it’s worsening or asymmetrical, warrants further investigation for Blount’s disease diagnosis.
Excluding Rickets and Skeletal Dysplasias
Nutritional rickets, caused by vitamin D deficiency, can also lead to bowleg deformities. However, rickets usually presents with other systemic signs and symptoms, and blood tests and specific radiographic features are different from Blount’s disease. Similarly, various skeletal dysplasias can cause bowlegs, but these are often associated with other skeletal abnormalities and have distinct radiographic patterns. A comprehensive Blount’s disease diagnosis process includes considering and excluding these alternative diagnoses through appropriate clinical and laboratory investigations when indicated.
Treatment Approaches Following Blount’s Disease Diagnosis
Once Blount’s disease diagnosis is confirmed, treatment strategies are determined based on the child’s age, severity of the condition, and radiographic findings. Treatment options range from non-surgical bracing to surgical interventions like guided-growth surgery or tibial osteotomy.
Non-Surgical Treatment: Bracing for Early Blount’s Disease
For children diagnosed with Blount’s disease at a young age, particularly those under three years old and with milder forms, bracing is often the initial treatment approach. Bracing aims to redirect growth and gradually correct the bowleg deformity.
Image alt text: Child wearing a brace, a non-surgical treatment method often used after Blount’s Disease diagnosis to correct bowlegs in young children.
Image alt text: Side view of a child in a Blount’s Disease brace, illustrating the brace’s design to support and gradually straighten the legs post-diagnosis.
Figures 3 & 4: Children with Blount’s disease undergoing brace treatment.
Bracing protocols typically involve using a knee-ankle-foot orthosis (KAFO) during waking hours, with the knee kept in full extension during weight-bearing activities. The effectiveness of bracing is monitored over a period, often up to a year. Regular follow-up appointments and repeat X-rays are essential to assess progress. If bracing fails to achieve gradual correction, or if Blount’s disease diagnosis is delayed and the deformity is significant at the outset, surgical intervention may be necessary.
Surgical Interventions for Blount’s Disease: Guided Growth and Osteotomy
Surgery is considered when bracing is unsuccessful, for older children at diagnosis, or when the bowleg deformity is severe (typically an angle greater than 13 degrees on standing X-ray). Surgical procedures for Blount’s disease primarily fall into two categories: guided-growth surgery and tibial osteotomy.
Guided-Growth Surgery: Modulating Growth Plate Activity
Guided-growth surgery is commonly employed for children and adolescents with Blount’s disease. This technique aims to correct the deformity by modulating the growth at the tibial growth plate.
Image alt text: Pre-operative photo of a child’s bowlegs due to Blount’s Disease, highlighting the deformity before guided growth surgical correction.
Image alt text: Rear view of a child with Blount’s Disease bowlegs before guided growth surgery, showing the extent of leg curvature.
Figures 5 & 6: Pre-operative clinical images of bowlegs in a child with Blount’s disease.
Small metal plates are affixed to the bone across the healthy, faster-growing side of the growth plate. This temporarily halts growth on that side, allowing the slower-growing, affected side to catch up. This differential growth modulation gradually straightens the leg over time.
Image alt text: Pre-operative X-ray for Blount’s Disease guided growth surgery, demonstrating the bone structure and deformity requiring correction.
Image alt text: Post-operative X-ray showing Blount’s Disease correction after guided growth surgery, with plates visible and leg alignment improved.
Figures 7 & 8: Pre-operative and post-operative X-rays illustrating guided growth correction of Blount’s disease.
Image alt text: Post-operative back view of a child’s legs after guided growth surgery for Blount’s Disease, showing corrected leg alignment.
Figures 9 & 10: Post-operative clinical images showing leg alignment after guided growth surgery.
Tibial Osteotomy: Correcting Deformity in Older Patients
Tibial osteotomy is considered when guided growth is not feasible, typically in older children and adolescents nearing skeletal maturity or when guided growth has failed. In this procedure, the tibia is surgically cut just below the knee, realigned to a corrected position, and then stabilized with a plate or external fixator until the bone heals in the straightened position.
Image alt text: Pre-operative photo of a child with Blount’s Disease before tibial osteotomy, showcasing the bowleg deformity requiring surgical correction.
Image alt text: Pre-operative X-ray for tibial osteotomy in Blount’s Disease, illustrating the tibial bone deformity before surgical realignment.
Figures 11 & 12: Pre-operative clinical and radiographic images prior to tibial osteotomy.
Image alt text: Post-operative photo after tibial osteotomy for Blount’s Disease, demonstrating the corrected leg alignment following surgery.
Image alt text: Post-operative X-ray showing Blount’s Disease correction after tibial osteotomy, with surgical hardware and improved bone alignment.
Figures 13 & 14: Post-operative clinical and radiographic images after tibial osteotomy, showing corrected leg alignment.
Adolescents with Blount’s disease might also have limb length discrepancies, which can be addressed during tibial osteotomy or require separate limb lengthening procedures.
External Fixators: Gradual Correction and Limb Lengthening
In cases requiring gradual correction, particularly when limb length discrepancy is also present, circular external fixators (spatial frames) are utilized. These devices allow for fine-tuning of leg alignment during the healing process. If X-rays reveal residual deformity, adjustments can be made to the fixator until optimal correction is achieved. External fixators are typically worn for 8 to 12 weeks.
Image alt text: Child with an external fixator on their leg as part of Blount’s Disease treatment, illustrating a method for gradual bone correction and stabilization.
Figure 9: Child with an external fixator for Blount’s disease treatment.
Rehabilitation and Physical Therapy After Blount’s Disease Treatment
Physical therapy is a vital component of Blount’s disease treatment, both after bracing and surgery. Rehabilitation programs focus on maintaining soft tissue flexibility, regaining muscle strength, and restoring normal joint function. Post-surgical physical therapy often involves sessions three times a week initially, gradually decreasing as healing progresses and function improves. Physical therapy ensures optimal outcomes and helps patients return to their normal activities after Blount’s disease diagnosis and treatment.
Updated: 8/5/2021
Images by the HSS Department of Radiology and Imaging
Authors
Shevaun Mackie Doyle, MD
Attending Orthopedic Surgeon, Hospital for Special Surgery
Associate Professor of Orthopedic Surgery, Weill Cornell Medical College
