Basics
Description
- Genu valgum (knock-knee) is angling of the knee(s) toward the midline, giving the appearance of the knees touching while the ankles are apart.
- Classified as physiologic and/or pathologic
- Physiologic genu valgum is a normal stage in the growth and development of healthy children between the ages of 2 and 7 years (1,2).
- Pathologic genu valgum if (2)
- The extent of angulation is greater than the mean for that particular age.
- The deformity persists beyond the age-appropriate progression of valgus.
- There is an underlying etiology.
Epidemiology
Prevalence
Physiologic genu valgum is a normal variant in children 2-7 years of age. It is more common in females than in males (1,3).
Etiology and Pathophysiology
- Physiologic genu valgum (1,3)
- Lower extremity alignment in childhood progresses from varus to valgus in the first 2 years of life.
- Around 2 years of age, lower extremity alignment progresses to valgus until it reaches a maximum (peak valgus angulation of 10-15 degrees) at approximately 4 years of age.
- Most children reach neutral adult alignment (~5 degrees) by 7 years of age.
- Etiologies of pathologic genu valgum include the following (1,2,3,4):
- Physeal/bone damage
- Trauma (e.g., proximal tibia metaphyseal)
- Infection
- Inflammatory disease (e.g., rheumatoid arthritis)
- Metabolic disease
- Rickets
- Renal osteodystrophy
- Skeletal dysplasias
- Pseudoachondroplasia
- Metaphyseal dysplasia
- Multiple epiphyseal dysplasia
- Neoplasms
- Multiple hereditary exostoses
- Osteochondromas
- Other benign tumors
- Other
- Iliotibial band tightness
- Vascular compromise
- Neuromuscular disease
- Obesity
- Idiopathic
Genetics
Idiopathic genu valgum is heritable.
Risk Factors
- Family history of genu valgum
- Proximal tibia metaphyseal fracture (Cozen fracture)
- Obesity (4)
Commonly Associated Conditions
Flat feet and external tibial torsion frequently accompany physiologic genu valgum. When present, this often accentuates the appearance of valgus.
Diagnosis
History
- Parental concern about the appearance of a child's legs often brings the condition to clinical attention. Other presentations include concerns about gait, falls, and lower extremity pain.
- Important historical elements include the following (1)[C],(2)[C],(4)[B]:
- Chief complaint/concern
- Appearance, gait disturbance, impaired function, or other symptom?
- Physiologic valgus is typically only cosmetic and not associated with other signs and symptoms.
- Onset and progression
- Physiologic valgus typically progresses between 2 and 4 years of age and improves between ages 4 and 7 years.
- Pathologic valgus typically worsens or presents after age 4 years (or in late childhood).
- Associated signs and symptoms
- Pain, limping, falls, and gait disturbances
- Medical history should include gestational, birth, and developmental history.
- Elicit previous medical therapies/outcomes (if any).
- History of trauma or infection
- Fractures in individuals with open growth plates may result in valgus deformities from abnormal healing.
- Infection may indicate physeal damage.
- Family history
- Lower extremity abnormalities, short stature, and skeletal dysplasia
Physical Exam
- Assess height and weight
- Plot on standardized growth curves. If height is less than 25th percentile, pathologic genu valgum is more likely (2).
- Obese children may develop idiopathic genu valgum (1)[C],(4)[B].
- Focused lower extremity examination (1)[C],(2)[C],(3)[C]
- Inspect for general appearance.
- Asymmetric genu valgum suggests underlying pathology.
- Palpate for other musculoskeletal abnormalities (e.g., bone and/or joint tenderness, exostoses).
- Assess leg length.
- Short lower extremities suggests potential skeletal dysplasia.
- Assess alignment, range of motion (ROM), and stability of hips, knees, ankles, and feet.
- Measure tibiofemoral angle (between long axis of tibia and long axis of femur). Peak valgus angulation is 10-15 degrees and occurs at approximately 4 years of age.
- Measure intermalleolar distance (distance between medial malleoli with medial femoral condyles touching). If >8 cm, the valgus is considered severe.
- Observe gait.
- Check for in-toeing and out-toeing.
- Suggests torsional deformities (e.g., metatarsus adductus, external tibial torsion)
Differential Diagnosis
- Genu valgum can be a normal (physiologic) developmental variant.
- Physiologic genu valgum is likely when
- The child's age is within the appropriate developmental stage (2,3,4,5,6,7 years of age).
- Valgus is symmetric.
- No associated signs or symptoms (e.g., pain, gait disturbance, joint swelling) are present.
- Normal height/weight
- Renal osteodystrophy is associated with pathologic genu valgum.
- Common skeletal dysplasias causing valgus deformities are metaphyseal dysplasia and pseudoachondroplasia.
- Pathologic genu valgum should be considered if
- It occurs before 2 years of age or after 7 years of age.
- Valgus deformity that is severe for age and developmental stage
- Valgus is asymmetric or unilateral.
- There is associated short stature.
- Valgus is accompanied by a history of metabolic condition, trauma, infection, abnormal bony growth (tumor), or joint changes (pain, tenderness, edema, warmth).
Diagnostic Tests & Interpretation
Initial Tests (lab, imaging)
- Labs: If an underlying metabolic problem is suspected, the following labs should be obtained:
- CBC
- CMP
- PTH
- 25-hydroxy vitamin D
- 1,25 dihydroxyvitamin D
- Imaging: Radiographs are not required for physiologic genu valgum.
- If clinical features are suggestive of pathologic valgus, the most clinically useful radiograph is a bilateral anterior-posterior (AP) view of the entire lower extremity. Films should be obtained with the patient in a standing position and with the patellae pointing straight ahead (1,3,5).
Treatment
General Measures
- No treatment is indicated for children <7 years of age with physiologic valgus. Clinical observation with appropriate parental education and reassurance are all that is necessary (2)[C],(6)[B].
- Orthotic braces are unnecessary for physiologic valgus.
- The management of pathologic genu valgum depends on the underlying cause. Medical therapy for the primary disease should be optimized.
- Surgical treatment should be considered in individuals >10 years of age with bothersome symptoms and/or significant deformity.
Issues for Referral
- Physiologic genu valgum persisting beyond 7-8 years of age should be referred to an orthopedic surgeon.
- If clinical features suggest pathologic valgum and/or an underlying condition, referral to an appropriate specialist should be made (2).
Surgery/Other Procedures
The two most common types of surgical treatment for pathologic genu valgum are tibial (and/or femoral) osteotomy and hemiepiphysiodesis.
- Corrective osteotomy is an option for correction of angular deformities of the lower extremity. However, it is a major, invasive procedure associated with severe complications, significant postoperative pain, and prolonged recovery time (8)[B].
- Hemiepiphysiodesis is a less invasive method that can be used to achieve lower extremity alignment in children with angulating deformities.
- This is an outpatient procedure that inhibits the growth plate unilaterally until the deformity is corrected.
- Contraindicated in individuals who have reached skeletal maturity (1)[C],(6)[B],(7)[B],(8)[B].
Ongoing Care
Follow-up Recommendations
- Children with physiologic genu valgum can be followed every 6-12 months with serial intermalleolar distances.
- Patients with pathologic genu valgum should be managed in consultation with appropriate specialist(s) based on the underlying etiology (1).
Patient Education
- Genu valgum is common in children during the first 7 years of life. Physiologic genu valgum spontaneously resolves as the child develops.
- Associated symptoms such as pain, gait disturbance, history of previous injury, or underlying medical conditions suggest a potential pathologic genu valgum and require additional evaluation.
Prognosis
- Physiologic genu valgum resolves spontaneously with normal growth and development.
- Pathologic genu valgum requires intervention. Improvement is multifactorial and based on successful
- Treatment of the underlying medical condition
- Intervention to correct any underlying orthopedic deformity
Complications
Angular deformities that persist can have biomechanical and functional consequences resulting in (1)[C],(8)[B] the following:
- Knee and foot pain
- Increased risk of lower extremity injuries such as meniscal tears and/or patellar subluxation
- Increased risk of osteoarthritis progression
- Gait abnormalities
References
1.Goldman V, Green D. Advances in growth plate modulation for lower extremity malalignment (knock knees and bow legs). Curr Opin Pediatr. 2010;22(1):47-53.
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2.Sass P, Hassan G. Lower extremity abnormalities in children. Am Fam Physician. 2003;68(3):461-468.
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3.Green WB. Genu varum and genu valgum in children: differential diagnosis and guidelines for evaluation. Compr Ther. 1996;22(1):22-29.
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4.Landauer F, Huber G, Paulmichl K, et al. Timely diagnosis of malalignment of the distal extremities is crucial in morbidly obese juveniles. Obes Facts. 2013;6(6):542-551.
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5.Scherl SA. Common lower extremity problems in children. Pediatr Rev. 2004;25(2):52-62.
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6.Boero S, Michelis MB, Riganti S. Use of the eight-Plate for angular correction of knee deformities due to idiopathic and pathologic physis: initiating treatment according to etiology. J Child Orthop. 2011;5(3):209-216.
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7.Courvoisier A, Eid A, Merloz P. Epiphyseal stapling of the proximal tibia for idiopathic genu valgum. J Child Orthop. 2009;3(3):217-221.
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8.Sharma L, Song J, Dunlop D, et al. Varus and valgus alignment and incident and progressive knee osteoarthritis. Ann Rheum Dis. 2010;69(11):1940-1945.
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Codes
ICD09
- 736.41 Genu valgum (acquired)
- 755.64 Congenital deformity of knee (joint)
- 268.1 Rickets, late effect
ICD10
- M21.069 Valgus deformity, not elsewhere classified, unspecified knee
- Q74.1 Congenital malformation of knee
- E64.3 Sequelae of rickets
- M21.061 Valgus deformity, not elsewhere classified, right knee
- M21.062 Valgus deformity, not elsewhere classified, left knee
SNOMED
- 299330008 knee joint valgus deformity (finding)
- 89689008 Congenital genu valgum (disorder)
- 52012001 acquired genu valgum (disorder)
- 250095008 Asymmetrical genu valgum (disorder)
Clinical Pearls
- Genu valgum is a normal physiologic process in children. It is essential to differentiate between physiologic and pathologic genu valgum.
- Characteristics of physiologic genu valgum include the following:
- Occurs between 2 and 7 years of age
- Valgus is symmetric.
- There are no associated symptoms (pain, limp).
- Not associated with conditions that might contribute to bony abnormalities (trauma, infection, family history)
- If physiologic genu valgum persists beyond 7-8 years of age, orthopedic referral is indicated.
- Clinical features suggestive of pathologic genu valgum should be referred for appropriate management.