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Genu Valgum

Basics

Description

- Neoplasms - Multiple hereditary exostoses - Osteochondromas - Other benign tumors

  • 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 damageTrauma (e.g., proximal tibia metaphyseal)InfectionInflammatory disease (e.g., rheumatoid arthritis)Metabolic diseaseRicketsRenal osteodystrophySkeletal dysplasiasPseudoachondroplasiaMetaphyseal dysplasiaMultiple epiphyseal dysplasiaNeoplasmsMultiple hereditary exostosesOsteochondromasOther benign tumorsOtherIliotibial band tightnessVascular compromiseNeuromuscular diseaseObesityIdiopathic

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/concernAppearance, gait disturbance, impaired function, or other symptom?Physiologic valgus is typically only cosmetic and not associated with other signs and symptoms.Onset and progressionPhysiologic 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 symptomsPain, limping, falls, and gait disturbancesMedical history should include gestational, birth, and developmental history.Elicit previous medical therapies/outcomes (if any).History of trauma or infectionFractures in individuals with open growth plates may result in valgus deformities from abnormal healing.Infection may indicate physeal damage.Family historyLower extremity abnormalities, short stature, and skeletal dysplasia

Physical Exam

  • Assess height and weightPlot 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 whenThe 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 ifIt occurs before 2 years of age or after 7 years of age.Valgus deformity that is severe for age and developmental stageValgus 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:CBCCMPPTH25-hydroxy vitamin D1,25 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 successfulTreatment of the underlying medical conditionIntervention 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 ageValgus 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.