Genu Valgum (Knock-Knee)

By admin On Jan 24, 2024

Ovid: 5-Minute Orthopaedic Consult

Editors: Frassica, Frank J.; Sponseller, Paul D.; Wilckens, John H.

Title: 5-Minute Orthopaedic Consult, 2nd Edition

> Table of Contents > Genu Valgum (Knock-Knee)

Genu Valgum (Knock-Knee)

Paul D. Sponseller MD

Basics

Description

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 (1,2).
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.

Epidemiology

Incidence

The condition is rare.
Pathologic valgus occurs in <1 per 1,000 (2).

Prevalence

It occurs in young children, usually 3–11 years old (1).
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).

Genetics

Many forms of rickets are transmitted genetically.
Idiopathic valgus may be transmitted in families.

Etiology

Physiologic genu valgum (Fig. 1)
Metabolic disorder (e.g., rickets)
Steroid dependence
Proximal tibia fracture (3,4)
Skeletal dysplasias
Chromosome disorders (e.g., Klinefelter syndrome)

Associated Conditions

Proximal tibia fracture
Pseudoachondroplasia
Renal osteodystrophy
Metaphyseal dysplasia
Rickets
Down syndrome

Diagnosis

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.

Fig. 1. This 3-year-old had typical physiologic genu valgum. It resolved with growth within 1 year.

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.

Tests

Lab

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

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.

P.153

Treatment

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 (3).
- Early tibial osteotomy should be avoided because of the high incidence of recurrence of valgus deformity (3).
- If an unacceptable degree of valgus remains after 1–2 years follow-up, hemiepiphysiodesis or osteotomy may be indicated (5,6).
Dysplasia:
- Children with pseudoachondroplasia and metaphyseal dysplasias are likely to develop genu valgum.
- Osteotomy may be necessary to correct the deformity.

Activity

No activity restrictions are necessary.

Special Therapy

Physical Therapy

Not indicated, because therapy and exercises cannot affect the growth of the limb

Surgery

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%.

Follow-up

Prognosis

Physiologic genu valgum resolves by age 7–10 years as long as it is mild (<15°) and no metabolic problems are present.

Complications

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.

References

1. Arazi
M, Ogun TC, Memik R. Normal development of the tibiofemoral angle in
children: a clinical study of 590 normal subjects from 3 to 17 years of
age. J Pediatr Orthop 2001;21:264–267.

2. White GR, Mencio GA. Genu valgum in children: diagnostic and therapeutic alternatives. J Am Acad Orthop Surg 1995;3:275–283.

3. Balthazar DA, Pappas AM. Acquired valgus deformity of the tibia in children. J Pediatr Orthop 1984;4:538–541.

4. Brougham DI, Nicol RO. Valgus deformity after proximal tibial fractures in children. J Bone Joint Surg 1987;69B:482.

5. Bowen JR, Torres RR, Forlin E. Partial epiphysiodesis to address genu varum or genu valgum. J Pediatr Orthop 1992;12:359–364.

6. Ferrick MR, Birch JG, Albright M. Correction of non-Blount’s angular knee deformity by permanent hemiepiphyseodesis. J Pediatr Orthop 2004;24:397–402.

Miscellaneous

Codes

ICD9-CM

736.41 Genu valgum

Patient Teaching

Inform parents that most cases of physiologic genu valgum begin to resolve spontaneously by 7 years of age.

FAQ

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.