Updated: 9/16/2022

Genu Valgum (knocked knees)

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  • summary
    • Genu Valgum is a normal physiologic process in children which may also be pathologic if associated with skeletal dysplasia, physeal injury, tumors or rickets. 
    • Diagnosis is made clinically with presence of progressive genu valgum after the age of 7. 
    • Treatment is observation for genu valgum <15 degrees in a child <7 years of age. Surgical management is indicated for severe and progressive genu valum in a child > 7 years of age. 
  • Epidemiology
    • Incidence
      • common but true incidence unknown 
    • Demographics
      • most common age of presentation 3-5 years
        • range 2-8 yrs
    • Anatomic location
      • distal femur is the more common location of pathological deformity 
    • Risk factors
      • prior infection or trauma 
      • vitamin D deficiency/rickets
      • obesity 
      • skeletal dysplasia
      • lysosomal storage diseases 
  • Etiology
    • Pathophysiology
      • physiologic progression of coronal alignment 
        • genu varum <2 years of age  
        • neutral alignment around 2 years
        • genu valgum will peak at 3-4 years to a tibiofemoral angle of 15-20 degrees 
        • genu valgum rarely worsens after age 7
          • after age 7 valgus should not be worse than 12 degrees of genu valgum
          • after age 7 the intermalleolar distance should be <8 cm
      • lateral deviation of mechanical axis
        • decreased growth from lateral physis relative to medial physis
      • patellar instability
        • increased Q-angle
        • shallow lateral femoral sulcus
          • lateral femoral condyle growth suppressed predisposing to lateral subluxation 
    • Associated conditions
      • bilateral genu valgum
        • physiologic
        • renal osteodystrophy (renal rickets)
        • skeletal dysplasia
          • Morquio syndrome
          • spondyloepiphyseal dysplasia
          • chondroctodermal dysplasia
      • unilateral genu valgum
        • physeal injury from trauma, infection, or vascular insult
        • proximal metaphyseal tibia fracture
          • Cozen Phenomenon 
        • benign tumors
          • fibrous dysplasia
          • osteochondromas
          • enchondromas 
        • fibular hemimelia 
  • Anatomy
    • Osteology 
      • knee
        • normal lateral distal femoral angle (LDFA) = 85-90 degrees 
        • normal medial proximal tibia angle (MPTA) = 85-90 degrees
        • hypoplastic lateral femoral condyle with shallow lateral femoral sulcus 
    • Ligament
      • medial collateral ligament 
        • 2 components 
          • superficial 
            • femoral attachment medial epicondyle 
            • tibial attachment proximal tibia deep and posterior to pes anserinus
          • deep MCL 
            • composed of meniscofemoral and meniscotibial ligaments
        • may be attenuated in genu valgum
    • Tendon 
      • increased combined lateral vector of quadricep and patellar tendon (increased q-angle)
        • predispose to patellar instability 
    • Nerves 
      • common peroneal nerve
        • branch off sciatic nerve that winds laterally around fibular neck 
        • bifurcates into two branches
          • superficial peroneal nerve
            •  innervates lateral compartment of leg which controls eversion of foot
          • deep peroneal 
            • innervates anterior compartment of leg which controls dorsiflexion 
    • Biomechanics
      • mechanical axis 
        • center of femoral head to center of ankle should pass through center of knee
        • lateral deviation of mechanical axis in genu valgum
          • lateral femoral condyle and lateral tibia plateau subjected to increased loads
      • mechanical loading on physis modulates growth
        • Hueter–Volkmann law
          • compression inhibits growth 
          • distraction stimulates growth
        • greater proportion of change in growth rate from hypertrophic zone (75%) than proliferative (25%)
          • greater effect on growth seen from change in size of chondrocytes than number 
  • classification
    • No uniform classification
      • unilateral vs bilateral
      • based on underlying etiology 
  • DIFFERENTIAL DIAGNOSIS
    • Physiologic genu valgum must be differentiated from pathologic causes
      • physiologic 
      • apparent 
        • obesity resulting in large thighs
        • excessive femoral anteversion 
        • excessive external tibial torsion  
      • idiopathic
      • post-traumatic 
        • Cozen phenomenon
        • malunion 
        • physeal arrest 
      • metabolic
        • renal osteodystrophy 
        • hypophosphatemic rickets 
      • infection 
        • osteomyelitis 
      • neuromuscular
        •  poliomyelitis 
      • neoplastic
        • multiple hereditary exostoses
        • fibrous dysplasia 
        • osteochondromas
      • lysosomal storage disease
        • mucopolysaccharidosis type IV (Morquio)
      • skeletal dysplasia
        • Chondroectodermal dysplasia (Ellis-van Creveld)
        • Spondyloepiphyseal dysplasia tarda
        • Pseudoachondroplasia 
        • Focal Fibrocartilaginous dysplasia 
  • PRESENTATION
    • History 
      • medical and family history can help differentiate between physiological and pathological etiology
    • Symptoms 
      • cosmetic deformity most common complaint
      • often asymptomatic 
      • medial sided knee pain
    • Physical exam
      • abnormal circumduction gait
      • inspection
        • hip adduction
        • medial aspect of knees touching
        • wide intermalleolar distance (>8 cm) 
        • leg lengths 
      • range of motion
        • assess patellar tracking 
      • rotational profile
        • apparent genu valgum with excessive femoral anteversion or external tibial torsion  
      • general exam to assess stigmata of associated conditions 
        • rickets 
        • syndromic features
        • skeletal dysplasias 
        • Maffucci syndrome 
  • IMAGING
    • Radiographs 
      • indication
        • asymmetrical findings
        • excessive genu valgum clinically age group beyond which is expected of physiologic changes
        • short stature
        • history of trauma or infection
        • limb length discrepancy 
      • views
        • AP standing long-length film 
          • patella should be facing forward to ensure proper positioning 
      • findings
        • lateral deviation of mechanical axis through knee
        • physeal narrowing or premature closing
        • Park-Harris lines
    • CT or MRI
      • rarely indicated
        • evaluate underlying malignancy
        • evaluate for physeal bar  
  • STUDIES 
    • lab studies 
      • depends on suspected underlying medical conditions
        • rickets
          • serum calcium and phosphate
          • 25-OH Vit D3 levels
          • PTH 
        • mucopolysaccharidoses
          • urinalysis for excess muscopolysaccharides (ie keratan sulfate - Morquio)
        • syndromic
          • genetic testing
  • TREATMENT
    • Nonoperative
      • indications
        • first line treatment 
        • tibiofemoral angle <15 degrees
        • children <7 years of age
      • modalities
        • observation and medical management 
        • bracing
          • rarely used
      • outcomes
        • vast majority of physiological genu valgum will resolve spontaneously 
        • medical management of underlying etiology may slow progression 
        • bracing may provide temporary relief but is an ineffective long-term solution
    • Operative
      • indications
        • tibiofemoral angle > 15 degrees
        • intramalleolar distance of 10 cm after age 10 years 
        • rapidly progressive deformity after age of 7  
      • modalities
        • medial hemiepiphysiodesis
          • temporary (more common) 
          • permanent
        • osteotomy 
          • distal femoral osteotomy 
          • high tibial osteotomy 
      • outcomes
        • eight-plate hemiepiphysiodesis
          • >95% complete correction for idiopathic 
          • 80% complete correction for pathological 
        • rate of correction with hemiepiphysiodesis is variable
          • angular correction of 7 degrees per year at the distal femur
          • angular correction of 5 degrees per year at the proximal tibia
  • TECHNIQUE
    • Observation
      • techniques
        • observation and reassurance 
    • Medial hemiepiphysiodesis  
      • indications
        • > 15-20° of valgus in a patient between ages 7-10
        • if line drawn from center of femoral head to center of ankle falls in lateral quadrant of tibial plateau in patient > 10 yrs of age
      • options
        • temporary hemiepiphysiodesis
          • rigid stapling
          • percutaneous screw (Metaizeau)
          • tension band plate and screws
        • permanent hemiepiphysiodesis
          • modified Phemister technique
      • technique
        • location of hemiepiphysiodesis dependent on 3 factors
          • amount of remaining growth
          • location of deformity
          • severity of deformity 
        • place extraperiosteally to avoid physeal injury 
        • implant placed midsagittal to avoid sagittal plane deformity 
        • one eight-plate or two staples per physis is generally sufficient
        • postop
          • follow patients often to avoid varus overcorrection 
          • implant removal
            • remove once mechanical axis passes through center or knee or slightly medial 
            • account for rebound medial overgrowth resulting in loss of correction
              • more likely in younger patients
          • growth begins within 24 months after removal of the tether
      • complications (~5-10%)
        • screw loosening or failure
        • rebound deformity after removal
        • infection
        • premature physeal closure
    • Osteotomy
      • indications
        • insufficient remaining growth to correct deformity with hemiepiphysiodesis
        • skeletally mature patients
        • non-functional growth plate (ie presence of bar, infection etc) 
      • options
        • lateral distal femur opening wedge osteotomy
          • pros
            • angular correction can be adjusted to desired correction
          • cons
            • requires grafting
            • less stable construct 
            • prolonged immobilization to allow graft to heal
        • medial distal femur closing wedge osteotomy
          • pros
            • stable osteotomy 
            • shorter period of immobilization
            • avoid distracting lateral common peroneal nerve
          • cons
            • technically demanding to remove precise angular wedge
        • high tibial osteotomy
      •  technique
        • determining site of osteotomy
          •  dependent on site of deformity 
            • assess mLDFA and mPMTA 
            • femur most common site of deformity
      •   complications
        • nonunion
        • neurovascular complication
        • compartment syndrome
        • hardware failure
  • complications
    • Peroneal nerve injury
      • risk factors
        • opening wedge technique
      • prevention
        • perform a peroneal nerve decompression at the time of surgery prior to distraction
          • two potential areas of entrapment
            • fascia of the lateral compartment
            • intermuscular septum separating the anterior and lateral compartments
        • gradual correction of severe deformities can be done with circular external fixator
    • Nonunion
      • risk factors
        • opening wedge osteotomy
        • >20 deg deformity 
    • Limb length discrepancy
      • closing wedge osteotomy shortens limb
      • opening wedge osteotomy lengthens limb
    • Undercorrection
      • insufficient physeal growth or encroaching maturity
    • Overcorrection
      • lost to follow-up (12%) 
    • Rebound phenomenon 
      • incidence
        • 56%
      • defined as a loss of 5 degrees of correction once the plate is removed
      • risk factors
        • femoral deformity
        • younger age at plate application and removal
        • faster correction rate 
        • intentional overcorrection increased risk
      • treatment 
        • consider slight overcorrection prior to implant removal 
          • may not prevent rebound growth but may limit recurrence of deformity
        • consider performing growth modulation closer to skeletal maturity for milder deformities
    • Physeal closure
      • very rare (<1%)
      • prevention
        • place implant extraperiosteally 
        • remove implant with 2-3 years after insertion
  • Prognosis
    • Idiopathic genu valgum has a better prognosis than pathological etiology with hemiepiphysiodesis
      • higher rate of complete correction 
      • faster correction rate
      • fewer complications
    • Physiologic genu valgum resolves spontaneous in vast majority by age of 7
    • Deformity after a proximal metaphyseal tibia fracture (Cozen) should be observed as most remodel
      • maximum magnitude of deformity reached approximately 12-18 mo after injury
      • resolve spontaneously within 2-4 years 
    • Threshold of deformity that leads to future degenerative changes is unknown

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(OBQ11.3) An 18-year-old girl presents with a deformity of the left leg that limits her ability to play basketball and volleyball. She reports pain along the lateral joint line with vigorous activity. A clinical image of the left leg in the supine position is shown in Figure A. A standing alignment radiograph is shown in Figure B with the mechanical lateral distal femoral angle measured at 73° (mLDFA 88°, range 85°-90°), an mechanical medial proximal tibial angle of 87° (mMPTA 87°, range 85°-90°), and a tibial femoral angle of 25°(range 5°-10°). Which of the following is the most appropriate surgical treatment?

QID: 3426
FIGURES:

Lateral closing wedge proximal femoral osteotomy with medial opening wedge tibial osteotomy

5%

(138/2936)

Lateral closing wedge tibial osteotomy

2%

(64/2936)

Medial opening wedge femoral osteotomy

8%

(231/2936)

Medial closing wedge tibial osteotomy

6%

(177/2936)

Medial closing wedge femoral osteotomy

78%

(2298/2936)

L 2 C

Select Answer to see Preferred Response

(OBQ11.13) A 12-year-old skeletally immature female presents with a several year history of bilateral knee pain and lower extremity deformity with her knees rubbing together while she runs. Her medical history is positive for asthma and eczema. She denies constitutional symptoms. She is neurovascularly intact in the bilateral lower extremities. A standing alignment radiograph is shown in Figure A. Which of the following treatment options is most appropriate?

QID: 3436
FIGURES:

Hip-knee-ankle-foot orthotic (HKAFO)

5%

(136/2918)

Distal femoral osteotomy with plate fixation of bilateral distal femurs

5%

(152/2918)

Temporary hemiepiphysiodesis across the bilateral medial distal femoral growth plates

76%

(2223/2918)

Temporary hemiepiphysiodesis across the right medial distal femoral growth plate

6%

(171/2918)

Temporary lateral hemiepiphysiodesis of the bilateral distal femoral growth plates

7%

(201/2918)

L 2 C

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