Genu Valgum

Overview

Definition

• Genu valgum is an angular deformity Deformity Examination of the Upper Limbs of the knee:
  • Apex pointing to the midline
  • Coronal Coronal Computed Tomography (CT) plane deformity Deformity Examination of the Upper Limbs of the lower extremity
  • Characteristic compensatory circumduction gait Gait Manner or style of walking. Neurological Examination
  • 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. Bones: Structure and Types disorders
• Colloquially known as “knock knees,” genu valgum is the Latin-derived term to describe the deformity Deformity Examination of the Upper Limbs. 

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 Deformity Examination of the Upper Limbs relative to the midline:
  • 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: apex displaced away from the midline
  • Genu valgum: apex displaced toward the midline

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. Bones: Structure and Types disorders

Etiology

Bilateral genu valgum:

• Physiologic:
  • Presents in ages 2–6 years 
  • Accounts for majority of cases
• Adolescent idiopathic Idiopathic Dermatomyositis genu valgum:
  • Typically bilateral
  • May be familial
• Metabolic (nutritional rickets Rickets Disorders caused by interruption of bone mineralization manifesting as osteomalacia in adults and characteristic deformities in infancy and childhood due to disturbances in normal bone formation. The mineralization process may be interrupted by disruption of vitamin d; phosphorus; or calcium homeostasis, resulting from dietary deficiencies, or acquired, or inherited metabolic, or hormonal disturbances. Osteomalacia and Rickets)
• Renal osteodystrophy Osteodystrophy Cirrhosis (renal rickets Rickets Disorders caused by interruption of bone mineralization manifesting as osteomalacia in adults and characteristic deformities in infancy and childhood due to disturbances in normal bone formation. The mineralization process may be interrupted by disruption of vitamin d; phosphorus; or calcium homeostasis, resulting from dietary deficiencies, or acquired, or inherited metabolic, or hormonal disturbances. 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 (Trisomy 21)
  • 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 Exostosis Benign hypertrophy that projects outward from the surface of bone, often containing a cartilaginous component. Yaws, Bejel, and Pinta
  • 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 Malunion Hip Fractures:
  • Distal femur 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
  • Proximal metaphyseal tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy 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
• 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 Benign Fibroadenoma tumors:
  • Fibrous Fibrous Fibrocystic Change dysplasia
  • Osteochondromas Osteochondromas Benign Bone Tumors
  • Ollier disease Ollier Disease Chondrosarcoma

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 Patella The flat, triangular bone situated at the anterior part of the knee. Knee Joint: Anatomy centered in the femoral sulcus
• Genu valgum alignment:
  • Defined by lateral displacement Displacement The process by which an emotional or behavioral response that is appropriate for one situation appears in another situation for which it is inappropriate. Defense Mechanisms of the mechanical axis
  • Lateral femoral condyle and the lateral plateau Plateau Cardiac Physiology of the tibia Tibia The second longest bone of the skeleton. It is located on the medial side of the lower leg, articulating with the fibula laterally, the talus distally, and the femur proximally. Knee Joint: Anatomy subjected to pathologic loading
  • Distal femur is the most common location of primary pathologic genu valgum.
  • Leads to inhibition of normal ossification Ossification The process of bone formation. Histogenesis of bone including ossification. Bones: Development and 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. Bones: Structure and Types and the development of a shallow femoral sulcus (where the patella Patella The flat, triangular bone situated at the anterior part of the knee. Knee Joint: Anatomy rests):
    • Propensity for patellar tilt and lateral patellar subluxation Subluxation Radial Head Subluxation (Nursemaid’s Elbow)
    • Patellofemoral joint Patellofemoral Joint The articulation between the articular surface of the patella and the patellar surface of the femur. Knee Joint: Anatomy becomes unstable
  • Medial collateral ligaments become stretched 
  • Severe deformity Deformity Examination of the Upper Limbs 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 Gait Manner or style of walking. Neurological Examination → progressive ligament laxity
    • Patient walks with a circumduction gait Gait Manner or style of walking. Neurological Examination
  • Long-term effects:
    • Lateral meniscal tears
    • Tibiofemoral subluxation Subluxation Radial Head Subluxation (Nursemaid’s Elbow)
    • 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: Histology attrition
    • Arthrosis of anterior (patellofemoral) lateral compartments of the knee
    • Osteochondral fractures

Clinical Presentation

History

• Parents describe a knock-kneed appearance and abnormal gait Gait Manner or style of walking. Neurological Examination.
• Family history Family History Adult Health Maintenance of specific heritable conditions:
  • Multiple exostosis Exostosis Benign hypertrophy that projects outward from the surface of bone, often containing a cartilaginous component. Yaws, Bejel, and Pinta
  • 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-free

Physical examination

• Angular deviation of the knee(s) in the coronal Coronal Computed Tomography (CT) plane
• Changes may be symmetrical Symmetrical Dermatologic Examination or asymmetrical.
• Physiologic genu valgum:
  • Generalized ligamentous laxity
  • ≤ 20 degrees of valgus angulation Angulation Buckle or Torus Fracture may be normal at 3–4 years of age.
  • Should resolve to ≤ 12 degrees of valgus angulation Angulation Buckle or Torus Fracture by age 7
• Evaluation of the gait Gait Manner or style of walking. Neurological Examination: circumduction typical
• Leg-length evaluation important
• Screen for other signs of genetic syndromes.

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 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. Bones: Structure and Types densitometry may be appropriate if underlying nutritional/ malabsorption Malabsorption General term for a group of malnutrition syndromes caused by failure of normal intestinal absorption of nutrients. Malabsorption and Maldigestion/metabolic disorder is present.

Imaging

X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests:

• 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 Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship beyond the age group for physiologic genu valgum 
  • Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship ＜ 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 Deformity Examination of the Upper Limbs 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. Bones: Structure and Types age and remaining growth potential

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. Bones: Structure and Types formation and mineralization:
    • Vitamin D Vitamin D A vitamin that includes both cholecalciferols and ergocalciferols, which have the common effect of preventing or curing rickets in animals. It can also be viewed as a hormone since it can be formed in skin by action of ultraviolet rays upon the precursors, 7-dehydrocholesterol and ergosterol, and acts on vitamin D receptors to regulate calcium in opposition to parathyroid hormone. Fat-soluble Vitamins and their Deficiencies
    • Calcium Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Electrolytes
    • 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

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 Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship who are at or near skeletal maturity.
    • Risk of peroneal nerve Peroneal nerve The lateral of the two terminal branches of the sciatic nerve. The peroneal (or fibular) nerve provides motor and sensory innervation to parts of the leg and foot. Popliteal Fossa: Anatomy injury mitigated by peroneal nerve Peroneal nerve The lateral of the two terminal branches of the sciatic nerve. The peroneal (or fibular) nerve provides motor and sensory innervation to parts of the leg and foot. Popliteal Fossa: Anatomy release.

Complications

• Due to failure to recognize pathologic genu valgum:
  • Continued progression of unrecognized underlying medical illness
  • Gait Gait Manner or style of walking. Neurological Examination disturbances
  • Premature Premature Childbirth before 37 weeks of pregnancy (259 days from the first day of the mother’s last menstrual period, or 245 days after fertilization). Necrotizing Enterocolitis arthritis Arthritis Acute or chronic inflammation of joints. Osteoarthritis
  • Chronic pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways
• 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 Overcorrection Volume Depletion and Dehydration or undercorrection
  • Neurovascular injury ( peroneal nerve Peroneal nerve The lateral of the two terminal branches of the sciatic nerve. The peroneal (or fibular) nerve provides motor and sensory innervation to parts of the leg and foot. Popliteal Fossa: Anatomy injury with osteotomy) 
  • Infection

Prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas

• 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 Rickets Disorders caused by interruption of bone mineralization manifesting as osteomalacia in adults and characteristic deformities in infancy and childhood due to disturbances in normal bone formation. The mineralization process may be interrupted by disruption of vitamin d; phosphorus; or calcium homeostasis, resulting from dietary deficiencies, or acquired, or inherited metabolic, or hormonal disturbances. Osteomalacia and Rickets and osteomalacia Osteomalacia Disorder caused by an interruption of the mineralization of organic bone matrix leading to bone softening, bone pain, and weakness. It is the adult form of rickets resulting from disruption of vitamin d; phosphorus; or calcium homeostasis. Osteomalacia and Rickets: disorders of decreased bone mineralization Bone mineralization Calcium (Ca2+) and phosphate (PO43–) combine to form hydroxyapatite crystals on the bone matrix. Bones: Development and Ossification. Rickets Rickets Disorders caused by interruption of bone mineralization manifesting as osteomalacia in adults and characteristic deformities in infancy and childhood due to disturbances in normal bone formation. The mineralization process may be interrupted by disruption of vitamin d; phosphorus; or calcium homeostasis, resulting from dietary deficiencies, or acquired, or inherited metabolic, or hormonal disturbances. Osteomalacia and 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: Histology of the epiphyseal growth plates Growth Plates The area between the epiphysis and the diaphysis within which bone growth occurs. Osteosarcoma in children, while osteomalacia Osteomalacia Disorder caused by an interruption of the mineralization of organic bone matrix leading to bone softening, bone pain, and weakness. It is the adult form of rickets resulting from disruption of vitamin d; phosphorus; or calcium homeostasis. 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. Bones: Structure and Types turnover in children and adults. Although most cases of rickets Rickets Disorders caused by interruption of bone mineralization manifesting as osteomalacia in adults and characteristic deformities in infancy and childhood due to disturbances in normal bone formation. The mineralization process may be interrupted by disruption of vitamin d; phosphorus; or calcium homeostasis, resulting from dietary deficiencies, or acquired, or inherited metabolic, or hormonal disturbances. Osteomalacia and Rickets and osteomalacia Osteomalacia Disorder caused by an interruption of the mineralization of organic bone matrix leading to bone softening, bone pain, and weakness. It is the adult form of rickets resulting from disruption of vitamin d; phosphorus; or calcium homeostasis. Osteomalacia and Rickets are due to vitamin D deficiency Vitamin D Deficiency A nutritional condition produced by a deficiency of vitamin D in the diet, insufficient production of vitamin D in the skin, inadequate absorption of vitamin D from the diet, or abnormal conversion of vitamin D to its bioactive metabolites. It is manifested clinically as rickets in children and osteomalacia in adults. Fat-soluble Vitamins and their Deficiencies, other genetic and nutritional disorders, as well as medications, can cause these disorders.
• Vitamin D deficiency Vitamin D Deficiency A nutritional condition produced by a deficiency of vitamin D in the diet, insufficient production of vitamin D in the skin, inadequate absorption of vitamin D from the diet, or abnormal conversion of vitamin D to its bioactive metabolites. It is manifested clinically as rickets in children and osteomalacia in adults. Fat-soluble Vitamins and their Deficiencies: state of deficiency of the forms of vitamin D Vitamin D A vitamin that includes both cholecalciferols and ergocalciferols, which have the common effect of preventing or curing rickets in animals. It can also be viewed as a hormone since it can be formed in skin by action of ultraviolet rays upon the precursors, 7-dehydrocholesterol and ergosterol, and acts on vitamin D receptors to regulate calcium in opposition to parathyroid hormone. Fat-soluble Vitamins and their Deficiencies, which alters the homeostasis Homeostasis The processes whereby the internal environment of an organism tends to remain balanced and stable. Cell Injury and Death of calcium Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Electrolytes 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: Anatomy.