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Genu Valgum (Knock-Knee)

  • Genu valgum, or knock-knee, is a normal phase of development in children 2-4 years old.
  • Girls normally have slightly more valgus of the knee than do boys.
  • The valgus straightens to achieve the adult position by 6-7 years of age.
  • Rickets, trauma, and genetic disorders also may cause genu valgum.
  • Some patients have an idiopathic valgus, not resulting from any of the foregoing disorders, that falls outside the normal limits and persists beyond 10 years of age.
  • Areas affected include the distal femoral and proximal tibial growth plates.
  • The condition is rare.
  • Pathologic valgus occurs in <1 per 1,000.
  • It occurs in young children, usually 3-11 years old.
  • Physiologic genu valgum is more common in females than in males.
Risk Factors
  • Family history of genu valgum
  • Proximal tibia metaphysic fracture in children (Cozen fracture); asymmetric overgrowth occurs and deformity is possible (parents should be warned about this possibility).
  • Many forms of rickets are transmitted genetically.
  • Idiopathic valgus may be transmitted in families.
  • Physiologic genu valgum
  • Metabolic disorder
  • Steroid dependence
  • Proximal tibia fracture
  • Skeletal dysplasias
  • Chromosome disorders (e.g., Klinefelter syndrome)
Associated Conditions
  • Proximal tibia fracture
  • Pseudoachondroplasia
  • Renal osteodystrophy
  • Metaphyseal dysplasia
  • Rickets
  • Down syndrome
Signs and Symptoms
  • Parental concern about the appearance of the child’s legs is the most common reason for presentation.
  • It is usually asymptomatic.
  • The knees usually are not painful in childhood but the physical appearance is sometimes bothersome; occasionally, valgus knees are associated with patellar discomfort.
  • In adulthood, valgus knees are more likely to produce arthritic symptoms outside of the joint.
Physical Exam
  • Measure the ROM of the knee.
  • Determine and plot height and weight percentiles for the patient’s age.
  • Measure the angle between the tibia and the femur with a goniometer.
  • Measure the distance between the ankles when the knees are touching (intermalleolar distance).
  • Assess the alignment and ROM in the adjacent hip and ankle.
  • Check the rotation of the limb and the gait.
  • Check the collateral ligaments of the knee for laxity.
  • Serum levels of calcium, phosphate, alkaline phosphatase, urea nitrogen, and creatinine should be measured if rickets or a metabolic problem is suspected.
  • The most common type of rickets in developed countries is familial hypophosphatemic rickets.
  • If rickets is to be evaluated, check vitamin D levels (25-hydroxy and 1,25-dihydroxy) as well as the other parameters.
  • Imaging of genu valgum, which is thought to be physiologic, is unnecessary for children <6 years old unless the patient has an asymmetric deformity or a pathologic condition is suspected.
  • An AP view of the lower extremity from the hip to ankle obtained while the patient is standing should be the 1st imaging study.
    • The knee should be pointing straight ahead.
    • The film cassette should be long enough to accommodate the entire extremity.
    • The femorotibial angle should be measured, and the site of the deformity should be identified as femoral, tibial, or both.
Differential Diagnosis
  • The main differential diagnosis is to determine whether the condition is physiologic or pathologic.
  • Physiologic genu valgum occurs without underlying rickets, dysplasia, or other known cause.
  • The most common skeletal dysplasias causing valgus are metaphyseal dysplasia and pseudoachondroplasia, as well as multiple osteochondromas.
General Measures
  • Physiologic valgus:
    • No treatment is indicated for physiologic genu valgum in patients <7 years old.
    • If the deformity persists after 7 years of age, hemiepiphysiodesis (at age 11-12 years) may be considered to achieve normal alignment.
      • Epiphysiodesis consists of slowing or stopping the growth plate on the medial side to allow the lateral side to catch up.
      • This relatively simple procedure does not substantially weaken the bone and allows early weightbearing.
  • Pathologic valgus:
    • For metabolic disorders, including renal osteodystrophy, the underlying condition should be treated.
    • Bracing has not been effective in preventing or reversing the deformity.
    • Single- or multiple-level osteotomy may be necessary to correct the deformity; medical control of the disease is needed first.
    • Usually, therapy is directed by a renal or endocrine specialist.
  • Fracture:
    • Follow-up of proximal tibia fracture should extend for several years after the injury.
    • Early tibial osteotomy should be avoided because of the high incidence of recurrence of valgus deformity.
    • If an unacceptable degree of valgus remains after 1-2 years follow-up, hemiepiphysiodesis or osteotomy may be indicated.
  • Dysplasia:
    • Children with pseudoachondroplasia and metaphyseal dysplasias are likely to develop genu valgum.
    • Osteotomy may be necessary to correct the deformity.
No activity restrictions are necessary.
Special Therapy
Physical Therapy
Not indicated, because therapy and exercises cannot affect the growth of the limb
  • 2 types of surgery commonly are used to correct valgus deformity when it persists: Hemiepiphysiodesis and varus osteotomy.
    • Epiphysiodesis aims to achieve satisfactory mechanical alignment at the end of growth.
    • Proximal tibia osteotomy should be considered if epiphysiodeses is not feasible.
      • Osteotomy involves a more difficult recovery period than epiphysiodesis because, in the former procedure, the bone is divided completely.
  • The overall success rate of surgery is >90%.
Physiologic genu valgum resolves by age 7-10 years as long as it is mild (<15°) and no metabolic problems are present.
  • Untreated genu valgum: If severe, the patient may develop patellofemoral pain and late degenerative arthritis from stresses on the lateral joint surface.
  • Surgical complications:
    • Infection
    • Compartment syndrome
    • Recurrence of deformity or overcorrection and neurovascular injury
Patient Monitoring
Children with idiopathic genu valgum may be followed every 12-24 months to determine whether the deformity is improving before a treatment decision is made.
736.41 Genu valgum
Patient Teaching
Inform parents that most cases of physiologic genu valgum begin to resolve spontaneously by 7 years of age.
Q: Is bracing indicated in genu valgum?
A: Bracing for valgus has never been shown to be effective. It is very cumbersome because the knee cannot bend in a corrective brace.
Q: Is valgus a cosmetic problem or a functional one?
A: In the more severe degrees, it can impair running and increase the risk of arthritis.

1 comment to Genu Valgum (Knock-Knee)

  • Vivian

    Hi. I have a knock knee but not both side , only left knee of leg.
    How to do my leg can be straight?
    Please email me. I would appreciate your help. Thanks!