Genu Valgum

Genu valgum is a deformation of the knee joint Knee joint The knee joint is made up of the articulations between the femur, tibia, and patella bones, and is one of the largest and most complex joints of the human body. The knee is classified as a synovial hinge joint, which primarily allows for flexion and extension with a more limited degree of translation and rotation. Knee Joint(s) that creates angulation of the lower limb(s) toward the midline in the coronal plane. Children ages 1–5 years are commonly affected. Many cases of genu valgum are physiologic and will resolve with further growth. However, it is critical to differentiate between normal physiologic changes and pathologic disorders, as pathologic cases can have serious long-term consequences if not corrected. Clinical presentation includes characteristic inward bowing of the lower limbs accompanied by gait disturbances. Diagnosis is clinical but may require support with diagnostic imaging. Management is often supportive but may require surgical intervention.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

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Overview

Definition

  • Genu valgum is an angular deformity of the knee:
    • Apex pointing to the midline
    • Coronal plane deformity of the lower extremity
    • Characteristic compensatory circumduction gait
    • Becomes evident when toddler begins to walk
  • Can be seen as a normal physiologic process during growth in healthy children:
    • Physiologic genu valgum: toddlers 2–6 years of age
    • Critical to differentiate between physiologic and pathologic genu valgum 
    • Can be related to hereditary, genetic, or metabolic bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones disorders
  • Colloquially known as “knock knees,” genu valgum is the Latin-derived term to describe the deformity. 

Classification

  • Bilateral
  • Unilateral
  • Distinguished from genu varum Genu varum Genu varum is a deformation of the knee joint(s) that creates angulation of the lower limb(s) away from the midline in the coronal plane. Children ages 1-5 years are commonly affected. Genu Varum by the direction of angular deformity relative to the midline:
    • Genu varum: apex displaced away from the midline
    • Genu valgum: apex displaced toward the midline
Genu varum and valgum

Genu varum and genu valgum: note the difference in angulation in the coronal plane.

Image by Lecturio. License: CC BY-NC-SA 4.0

Epidemiology

  • Generally presents between ages 3 and 10 years
  • Present in 10% of schoolchildren 
  • More common among overweight or obese schoolchildren
  • Can be familial, associated with trauma, rheumatologic diseases, or metabolic bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones disorders

Etiology

Bilateral genu valgum:

  • Physiologic:
    • Presents in ages 2–6 years 
    • Accounts for majority of cases
  • Adolescent idiopathic genu valgum: 
    • Typically bilateral
    • May be familial
  • Metabolic (nutritional rickets Rickets Rickets and osteomalacia are disorders of decreased bone mineralization. Rickets affects the cartilage of the epiphyseal growth plates in children. Although most cases of rickets are due to vitamin D deficiency, other genetic and nutritional disorders as well as medications can cause these disorders. Rickets commonly presents with skeletal deformities and growth abnormalities. Osteomalacia and Rickets)
  • Renal osteodystrophy (renal rickets Rickets Rickets and osteomalacia are disorders of decreased bone mineralization. Rickets affects the cartilage of the epiphyseal growth plates in children. Although most cases of rickets are due to vitamin D deficiency, other genetic and nutritional disorders as well as medications can cause these disorders. Rickets commonly presents with skeletal deformities and growth abnormalities. Osteomalacia and Rickets)
  • Genetic/chromosomal disorders:
    • Down syndrome Down syndrome Down syndrome, or trisomy 21, is the most common chromosomal aberration and the most frequent genetic cause of developmental delay. Both boys and girls are affected and have characteristic craniofacial and musculoskeletal features, as well as multiple medical anomalies involving the cardiac, gastrointestinal, ocular, and auditory systems. Down Syndrome
    • Marfan syndrome Marfan syndrome Marfan syndrome is a genetic condition with autosomal dominant inheritance. Marfan syndrome affects the elasticity of connective tissues throughout the body, most notably in the cardiovascular, ocular, and musculoskeletal systems. Marfan Syndrome
    • Neurofibromatosis
    • Hereditary multiple exostosis
    • Osteogenesis imperfecta Osteogenesis imperfecta Osteogenesis imperfecta (OI), or "brittle bone disease," is a rare genetic connective tissue disorder characterized by severe bone fragility. Although OI is considered a single disease, OI includes over 16 genotypes and clinical phenotypes with differing symptom severity. Osteogenesis Imperfecta
  • Skeletal dysplasia:
    • Morquio syndrome
    • Spondyloepiphyseal dysplasia
    • Chondroectodermal dysplasia

Unilateral genu valgum:

  • Physeal injury: 
    • Trauma
    • Infection
    • Vascular insult
  • Fracture Fracture A fracture is a disruption of the cortex of any bone and periosteum and is commonly due to mechanical stress after an injury or accident. Open fractures due to trauma can be a medical emergency. Fractures are frequently associated with automobile accidents, workplace injuries, and trauma. Overview of Bone Fractures malunion:
    • Distal femur fracture
    • Proximal metaphyseal tibia fracture
  • Poliomyelitis Poliomyelitis Poliomyelitis is an infectious disease caused by the poliovirus. Transmission occurs through the fecal-oral route and through respiratory aerosols. The majority of patients will be asymptomatic or have a mild, abortive presentation with flu-like symptoms. Those who develop nonparalytic poliomyelitis will develop signs and symptoms of aseptic meningitis. A very minor proportion of patients will progress to paralytic poliomyelitis. Poliovirus/Poliomyelitis
  • Benign tumors:
    • Fibrous dysplasia
    • Osteochondromas
    • Ollier disease

Pathophysiology

  • Normal alignment:
    • Lower-extremity lengths are equal.
    • Mechanical axis bisects the knee in the anatomical position.
    • Balanced load on the medial and lateral compartments of the knee
    • Balanced load on the collateral ligaments
    • Patella centered in the femoral sulcus
  • Genu valgum alignment:
    • Defined by lateral displacement of the mechanical axis
    • Lateral femoral condyle and the lateral plateau of the tibia subjected to pathologic loading
    • Distal femur is the most common location of primary pathologic genu valgum.
    • Leads to inhibition of normal ossification of the epiphysis Epiphysis The head of a long bone that is separated from the shaft by the epiphyseal plate until bone growth stops. At that time, the plate disappears and the head and shaft are united. Structure of Bones and the development of a shallow femoral sulcus (where the patella rests):
      • Propensity for patellar tilt and lateral patellar subluxation
      • Patellofemoral joint becomes unstable
    • Medial collateral ligaments become stretched 
    • Severe deformity leads to: 
      • Knee pain Knee Pain Knee pain is a common presentation to primary care physicians. The diagnosis can be challenging as the pain may arise from the joint, surrounding tissues, or referred to the joint from distant structures. The differential diagnosis of knee pain is broad and categorizing the various diagnoses related to the timing (acute or chronic) is useful. Knee Pain 
      • Tibial thrust during gait → progressive ligament laxity
      • Patient walks with a circumduction gait
    • Long-term effects:
      • Lateral meniscal tears
      • Tibiofemoral subluxation
      • Patellofemoral dislocation
      • Progressive joint laxity
      • Articular cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage attrition
      • Arthrosis of anterior (patellofemoral) lateral compartments of the knee
      • Osteochondral fractures

Clinical Presentation

History

  • Parents describe a knock-kneed appearance and abnormal gait.
  • Family history of specific heritable conditions: 
    • Multiple exostosis
    • Osteogenesis imperfecta Osteogenesis imperfecta Osteogenesis imperfecta (OI), or "brittle bone disease," is a rare genetic connective tissue disorder characterized by severe bone fragility. Although OI is considered a single disease, OI includes over 16 genotypes and clinical phenotypes with differing symptom severity. Osteogenesis Imperfecta
    • Marfan syndrome Marfan syndrome Marfan syndrome is a genetic condition with autosomal dominant inheritance. Marfan syndrome affects the elasticity of connective tissues throughout the body, most notably in the cardiovascular, ocular, and musculoskeletal systems. Marfan Syndrome
  • Natural history of physiologic genu valgum:
    • Resolves by age 6
    • Lacks functional restrictions
    • Pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain-free

Physical examination

  • Angular deviation of the knee(s) in the coronal plane
  • Changes may be symmetrical or asymmetrical.
  • Physiologic genu valgum:
    • Generalized ligamentous laxity
    • ≤ 20 degrees of valgus angulation may be normal at 3–4 years of age.
    • Should resolve to ≤ 12 degrees of valgus angulation by age 7
  • Evaluation of the gait: circumduction typical
  • Leg Leg The lower leg, or just "leg" in anatomical terms, is the part of the lower limb between the knee and the ankle joint. The bony structure is composed of the tibia and fibula bones, and the muscles of the leg are grouped into the anterior, lateral, and posterior compartments by extensions of fascia. Leg-length evaluation important
  • Screen for other signs of genetic syndromes.
Genu valgum

Pathologic genu valgum:
This child with rickets Rickets Rickets and osteomalacia are disorders of decreased bone mineralization. Rickets affects the cartilage of the epiphyseal growth plates in children. Although most cases of rickets are due to vitamin D deficiency, other genetic and nutritional disorders as well as medications can cause these disorders. Rickets commonly presents with skeletal deformities and growth abnormalities. Osteomalacia and Rickets has developed genu valgum, most notably in the right knee.

Image: “Showing genu valgum” by Bahadure RN, Thosar N, Kriplani R, Baliga S, Fulzele P. License: CC BY 3.0

Diagnosis

Diagnosis is primary based on clinical examination. It is critical to differentiate between normal physiologic genu valgum and a pathologic process.

Diagnostic evaluation

  • Physiologic genu valgum is a common normal variant in toddlers:
    • Asymptomatic and symmetric
    • Resolves by age 6–7 
  • Symptomatic or unilateral genu valgum should be referred to an orthopedist.
  • Laboratory evaluation aims to uncover underlying syndrome or disorder:
    • Renal function
    • Vitamin/mineral levels
  • Bone densitometry may be appropriate if underlying nutritional/ malabsorption Malabsorption Malabsorption involves many disorders in which there is an inability of the gut to absorb nutrients from dietary intake, potentially including water and/or electrolytes. A closely related term, maldigestion is the inability to break down large molecules of food into their smaller constituents. Malabsorption and maldigestion can affect macronutrients (fats, proteins, and carbohydrates), micronutrients (vitamins and minerals), or both. Malabsorption and Maldigestion/metabolic disorder is present.

Imaging

X-ray:

  • Not indicated in cases of physiologic genu valgum
  • Indications for X-rays X-rays X-rays are high-energy particles of electromagnetic radiation used in the medical field for the generation of anatomical images. X-rays are projected through the body of a patient and onto a film, and this technique is called conventional or projectional radiography. X-rays:
    • Asymmetrical genu valgum 
    • Excessive genu valgum
    • Patients beyond the age group for physiologic genu valgum 
    • Patients < 10th percentile height for their age with genu valgum
    • History of trauma involving the knee
    • Concern for infection
  • Standing anteroposterior (AP) radiography of the lower extremities:
    • Taken with patellae facing forward 
    • Allows visualization of true and apparent limb lengths and deformities
  • Mechanical axis determination:
    • Line drawn from the center of femoral head to center of ankle
    • Line should bisect the knee
    • Genu valgum shows lateral deviation of the axis toward or beyond the joint margin.
  • Deformity may be femoral, tibial, or both. 
  • AP radiography of wrist to determine bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones age and remaining growth potential
X-ray of a child with genu valgum

X-ray of a child with genu valgum

Image: “ Mutation Mutation Genetic mutations are errors in DNA that can cause protein misfolding and dysfunction. There are various types of mutations, including chromosomal, point, frameshift, and expansion mutations. Types of Mutations study for a six-year-old girl with genu valgum” by Kaustuv Bhattacharya, et al. License: CC BY 4.0, cropped by Lecturio.

Management

The majority of cases of genu valgum are physiologic and should resolve spontaneously; thus, they require only observation and expectant management. 

Nonoperative management

Observation:

1st-line treatment, appropriate if:

  • Patient is within the age range for physiologic genu valgum.
  • Tibiofemoral angle is < 15 degrees.
  • Child is < 6 years of age.

Medical management: 

  • Indicated in cases of underlying medical conditions and metabolic disorders:
    • Correct nutritional deficiencies.
    • Optimize bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones formation and mineralization:
      • Vitamin D
      • Calcium
      • Bisphosphonates Bisphosphonates Bisphosphonates are pyrophosphate analogs most well-known for treating osteoporosis by preventing bone loss. Bisphosphonates end in the suffix "-dronate" or "-dronic acid" (e.g., alendronate, risedronate, pamidronate) and bind to hydroxyapatite crystals in bone, inhibiting osteoclast-induced bone resorption. Bisphosphonates
  • Bracing:
    • Not necessary for physiologic genu valgum 
    • Not effective for pathologic genu valgum
Reduction in genu valgum

Reduction in genu valgum:
Improved valgus deformity in a 9-year-old child with rickets Rickets Rickets and osteomalacia are disorders of decreased bone mineralization. Rickets affects the cartilage of the epiphyseal growth plates in children. Although most cases of rickets are due to vitamin D deficiency, other genetic and nutritional disorders as well as medications can cause these disorders. Rickets commonly presents with skeletal deformities and growth abnormalities. Osteomalacia and Rickets at 1-year follow-up after vitamin D therapy.

Image: “Reduction in the genu valgum deformity in a 9-year-old child at 1-year follow-up” by Journal of Clinical Research in Pediatric Endocrinology. License: CC BY 2.5

Surgical management

  • Indicated in severe pathologic genu valgum
  • Surgical options:
    • Guided growth with hemiepiphysiodesis or physeal tethering:
      • Indicated for > 15–20 degrees of valgus in children < 10 years of age 
      • Reversible and minimally invasive 
      • Extraperiosteally placed implants (plates and screws)
      • Implant serves as a tension band for gradual growth changes.
    • Distal femoral varus osteotomy:
      • Indicated in patients who are at or near skeletal maturity.
      • Risk of peroneal nerve injury mitigated by peroneal nerve release.

Complications

  • Due to failure to recognize pathologic genu valgum:
    • Continued progression of unrecognized underlying medical illness
    • Gait disturbances
    • Premature arthritis
    • Chronic pain
  • Surgical complications Surgical complications Surgical complications are conditions, disorders, or adverse events that occur following surgical procedures. The most common general surgical complications include bleeding, infections, injury to the surrounding organs, venous thromboembolic events, and complications from anesthesia. Surgical Complications:
    • Hardware failure is much less common with newer implants.
    • Physeal injuries due to implants: less common with guided-growth method
    • Overcorrection or undercorrection
    • Neurovascular injury (peroneal nerve injury with osteotomy) 
    • Infection

Prognosis

  • Most cases of physiologic genu valgum resolve spontaneously. 
  • Results of cases of pathologic genu valgum using guided-growth techniques with close follow-up are generally positive.

Clinical Relevance

  • Rickets and osteomalacia Osteomalacia Rickets and osteomalacia are disorders of decreased bone mineralization. Osteomalacia affects the sites of bone turnover in children and adults. Although most cases are due to vitamin D deficiency, other genetic and nutritional disorders as well as medications can cause these disorders. Osteomalacia can present with bone pain, difficulty with ambulation and pathologic fractures. Osteomalacia and Rickets: disorders of decreased bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones mineralization. Rickets affects the cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage of the epiphyseal growth plates in children, while osteomalacia Osteomalacia Rickets and osteomalacia are disorders of decreased bone mineralization. Osteomalacia affects the sites of bone turnover in children and adults. Although most cases are due to vitamin D deficiency, other genetic and nutritional disorders as well as medications can cause these disorders. Osteomalacia can present with bone pain, difficulty with ambulation and pathologic fractures. Osteomalacia and Rickets affects the sites of bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones turnover in children and adults. Although most cases of rickets Rickets Rickets and osteomalacia are disorders of decreased bone mineralization. Rickets affects the cartilage of the epiphyseal growth plates in children. Although most cases of rickets are due to vitamin D deficiency, other genetic and nutritional disorders as well as medications can cause these disorders. Rickets commonly presents with skeletal deformities and growth abnormalities. Osteomalacia and Rickets and osteomalacia Osteomalacia Rickets and osteomalacia are disorders of decreased bone mineralization. Osteomalacia affects the sites of bone turnover in children and adults. Although most cases are due to vitamin D deficiency, other genetic and nutritional disorders as well as medications can cause these disorders. Osteomalacia can present with bone pain, difficulty with ambulation and pathologic fractures. Osteomalacia and Rickets are due to vitamin D deficiency, other genetic and nutritional disorders, as well as medications, can cause these disorders.
  • Vitamin D deficiency: state of deficiency of the forms of vitamin D, which alters the homeostasis of calcium due to deficient absorption Absorption Absorption involves the uptake of nutrient molecules and their transfer from the lumen of the GI tract across the enterocytes and into the interstitial space, where they can be taken up in the venous or lymphatic circulation. Digestion and Absorption in the diet and reabsorption in the kidneys Kidneys The kidneys are a pair of bean-shaped organs located retroperitoneally against the posterior wall of the abdomen on either side of the spine. As part of the urinary tract, the kidneys are responsible for blood filtration and excretion of water-soluble waste in the urine. Kidneys.

References

  1. Browner, B., Jupiter, J., Krettek, C., Anderson, P. (2020). Skeletal Trauma: Basic Science, Management, and Reconstruction. Philadelphia: Elsevier.
  2. Patel, M., Nelson, R. (2021). Genu valgum. StatPearls. Retrieved June 23, 2021, from http://www.ncbi.nlm.nih.gov/books/NBK559244/ 
  3. Rosenfeld, S.B. (2021). Approach to the child with knock-knees. In Torchia, M.M., UpToDate. Retrieved June 24, 2021, from https://www.uptodate.com/contents/approach-to-the-child-with-knock-knees
  4. Kliegman, R., et al. (2020). Nelson Textbook of Pediatrics. Philadelphia: Elsevier.
  5. Zitelli, B., McIntire, S., Nowalk, A. (2018). Zitelli and Davis’ Atlas of Pediatric Physical Diagnosis. Philadelphia: Elsevier.
  6. Murthy, D., De Leucio, A. (2021). Blount disease. StatPearls. Retrieved June 24, 2021, from http://www.ncbi.nlm.nih.gov/books/NBK560923/

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