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Genu Varum (Section 110)
Genu varum (Latin: genu “knee”, varum “bent outwards”), also called bow-leggedness, bandiness, bandy-leg, or tibia vara, is a varus deformity marked by outward bowing of the knee. This means the lower leg is angled inward (medially) in relation to the thigh’s axis, which gives the limb the overall appearance of an archer’s bow and is the reason for the term ‘bow-legged’. Rickets is a common cause of genu varum.

First Classification of Genu Varum
The first recorded account of genu varum dates back to a painting completed in 1509 by Hans Burgkmair (1473-1531), The Virgin and Child. The Virgin and Child depicts a child with symptoms of bowed legs. According to Cone, the bowed legs of the child in the painting are most closely associated with symptoms of rickets disease.

First Instances of Genu Varum in Literature
In 1645, Daniel Whistler (1619-1684) published his thesis: De Morbo Puerili Anglorum quem Patrio Idiomate Indigenae Vocant The Rickets ("Concerning a disease of English children which is popularly called the Rickets"). Whistler’s fourteen-page thesis is the first account defining rickets as a disease associated with specific symptoms. Five years later, in 1650 Francis Glisson (1597-1677) published a much more in-depth study into rickets and bow legs. Although Glisson’s book came after Whistler’s thesis, De Rachitide (1650) is seen as the the first substantial analysis of the disease and credit for the first analysis of rickets is given to Glisson.

The Renaissance
During the Renaissance in Europe, genu varum was prevalent in children. This prevalence was due to a limited exposure of sunlight, especially in wealthy families as children did not play outside frequently. Additionally, breast-feeding into older ages and lack of a solid food diet led to rickets in children, a disease that leads to genu varum.

Industrial Revolution
The Industrial Revolution was a time in which rickets was frequent in the British Isles. This led to genu varum in children as they suffered from dietary deficiencies and the environmental issue of smog. Smog created a physical block to sunlight, and this decreased exposure to UV radiation led to vitamin D deficiency. Furthermore, weather patterns of frigid winters followed by humid summers in England led to children staying indoors. This pattern of increased time spent inside likely led to rickets becoming more common in England. Rickets then led to genu varum, and became nicknamed the “English Disease” during pre-Industrial Revolution times.

World War I
World War I posed issues for families in Vienna, Budapest, and Berlin. Limited food supplies in many countries, less ability to spend time outside, and poorly organized orphanages led to increases in cases of rickets across many European countries. This increase was mostly observed in children and young adolescents, and led to visible genu varum. Once World War II took hold, many countries implemented programs for vitamin D supplements, decreasing the frequency of rickets, and along with it the frequency of genu varum.

Genu Varum in Athletes
A study conducted by Asadi and colleagues found that soccer players had a higher occurrence of genu varum than non-soccer players with an especially high prevalence in soccer players between ages 16-18. Similarly, Witvrouw and colleagues found that males between 16-18 years old who engage in vigorous soccer training have increased degrees of genu varum as a result of the training. Exercise that places pressure or tension on the knee results in misalignment of the muscle and skeleton and can lead to bow legs. In a comparative study of different high-performing athletes, Yaniv and colleagues discovered that soccer players had a notably greater occurrence of genu varum than tennis players. Espandar and colleagues conclude that because frequent and strenuous soccer playing significantly increases the degree of genu varum in 16- to 18-year-old males, attempts should be made to lessen genu varum amongst these athletes.

Cowboys
In popular culture, cowboys have been affiliated with bowleggedness. Cartoons have been drawn depicting cowboys suffering from genu varum. In the New Yorker Magazine, Toro illustrates a cowboy with bowleggedness. Songs call cowboys bow-legged; sometime going so far as to refer to cowboys as “bowlegs.”

This association of cowboys with bowleggedness in the arts carries over to real life as well. According to Hyde, customers in cowboy clothes shops initially stand with their knees out, imitating the stereotypically bow-legged posture of cowboys.

Diagnosis
There are several symptoms that should be noted when diagnosing genu varum. Shortened limbs relative to the trunk suggests a dwarfing condition. Both limbs should be checked for asymmetry and alignment in the frontal and sagittal planes. Passive rotation of the hips may also be indicative of genu varum. In a patient with genu varum, there is often an angular deformity which will be visible in the distal femur, the knee, or the proximal tibia. The presence of genu varum past the age of two is considered abnormal.

Blount's Disease
Blount's disease is a deformity in the legs, mostly from the knees to the ankles. This disease is due to osteochondrosis that inhibits bone growth on the medial side of the tibia. This leads to asymmetric growth on the medial and lateral sides of the bone. As a result, the affected bone curves outward and forms the usual "archers bow" which is sometimes called "bow-legs."

There are two main types of Blount's disease: infantile and late-onset, based on the age of onset. The first type is infantile or early-onset, where children under four years of age are diagnosed with the disease. The second type of Blount's disease is late-onset, found mostly in older children and teenagers. Both of these are acquired growth disorders, but the age of onset can determine the course of treatment.

Rickets
Rickets is a disease that results in softening and weakening of bones in children. It arises from a multitude of factors, most notably nutritional deficiency of calcium and vitamin D, a prohormone essential in the absorption of calcium in the gut. Non-nutritional causes include renal tubular acidosis and inherited genetic defects.

Causes of rickets are characterized in two ways: calcipenic rickets and phosphophenic rickets. Calcipenic (hypocalcemic) rickets results from deficiency of calcium or vitamin D usually as a result of diet. A mineralization defect as a result of calcium deficiency results in the accumulation of osteoid within bone tissue and leads to its weakening. Vitamin D deficiency is the most common cause of rickets rather than mineral deficiencies alone. Phosphenic (hypophosphatemic) rickets results from phosphate deficiency (in the case of renal tubular acidosis) in which poor mineral resorption in the kidneys leads to deficient bone mineralization. Because of deficient mineralization of calcium and phosphate at the open growth plate, bones fail to properly mature and harden, which leads to weakening and bowing due to compression over time.

Osteomalacia
The adult equivalent of rickets is osteomalacia and it can cause severe skeletal deformities that include genu varum

Skeletal Dysplasias (Osteochondrodysplasias)
The skeletal dysplasias are associated with abnormalities in the development and maintenance of the appendicular and axial skeleton. Abnormality due to Metaphyseal Chondrodysplasia can cause progressive bowing of the legs.

Bacterial Infection and Bone Deformity
Although rare, osteomyelitis can lead to the development of genu varum.

Occupational Causes and Physical Trauma
The remaining causes are occupational, especially among jockeys, and from physical trauma, the condition being very likely to supervene after accidents involving the condyles of the femur. [1]

Jockeys
The popularity of sports among adolescents has brought attention to occurences of genu varum in jockeys. Genu varum is prevalent in adolescent soccer players during the last two years of their skeletal growth. Playing a sport during a time of growth in adolescence can impose high amounts of stress and strain on the knee joint. Movements such as a sudden change of direction while running will increase the amount of strain on the knee joint. The amount and the duration of stress due to intensive sport training can intensify the severity of growth deformities such as genu varum.

Childhood
Children display a degree of genu varum until the age of three-to-four. A child sits with the soles of the feet facing one another; the tibia and femur are curved outwards; and, if the limbs are extended, although the ankles are in contact, there is a distinct space between the knee-joints. During the first year of life, a gradual change takes place. The knee-joints approach one another; the femur slopes downward and inward towards the knee joints; the tibia become straight; and the sole of the foot faces almost directly downwards.

While these changes are occurring, the bones, which at first consist principally of cartilage, are gradually becoming ossified. When the child is able to stand, gravity pushes on the lower limbs. This results in either inward or outward tibial and femoral bowing, which is known as genu valgum and genu varum, respectively. Even prior to an infant starting to walk, the forces placed on the limb bones can result in bone deformation. By the time a normal child begins to walk, the lower limbs are prepared, both by their general configuration and by the rigidity of the bones which form them, to support the weight of the body.[1]

Risk Factors
Minor genu varum (<2°) does not have any adverse effects on the foot as long as the subtalar joint is normal. Severe genu varum is the most frequent deformity seen in patients with osteoarthritic knees. An ACL rupture caused by the loss of medial meniscus can lead to genu varum. The medial meniscus can be damaged if the center of rotation of the knee is shifted medially. There is currently no solid evidence as to whether or not genu varum predisposes athletes to any specific lower limb injuries, but there is an association between genu varum and pain. However, genu varum along with genu valgum, genu recurvatum, and excessive Q-angle may be associated with an increased risk of overuse training-related injury.

Signs and Symptoms
Signs of bow-leggedness are easily recognized visually and are most apparent in children at six months old. The most obvious sign is a convex shape of the legs, where legs are bowed outward and the knees are further apart than usual. In general, children and adults with genu varum have asymmetry or misalignment as examined from the front or the side. A more subtle sign in children and adults is the crease behind the knee not being parallel to the ground, also known as obliquity of the popliteal crease. In children, an awkward gait and turning in of the feet are other common signs. However, genu varum should not cause any developmental delays for toddlers to walk.

There are usually no symptoms of genu varum in children, outside of occasional tripping. In adolescence and adulthood, genu varum may cause discomfort or pain in hips, outer parts of the knees, and ankles due to uneven stress. If left untreated in adults, the abnormal wear and stress on knees may lead to early onset arthritis.

Blount's Disease
Detecting Blount’s Disease in children is a similar process to detecting genu varum. Usually, an orthopedist will perform a physical examination and an X-ray of the legs (Neal, 2017). In determining diagnosis, one distinguishing feature is the growth patterns at the top of the tibia. Blount’s disease will put pressure on the tibia’s growth plate, which leads to abnormal growth of the tibia, and later bow-leggedness. However, Blount’s disease can be more serious in older adolescents, as the varus deformity for adolescents can be greater than that of infants. Therefore, if not diagnosed early enough, adolescents may experience more discomfort as a result of untreated Blount’s disease.

When using an X-ray for diagnosis, several measurements are taken of the angles of the leg in the radiograph of the patient. These measurements are useful for distinguishing Blount’s disease from typical bone growth, as well as measuring how far the disease progresses over time. These angles include the anatomic lateral distal femoral angle (aLDFA), anatomic lateral distal tibial angle (aLDTA), and tibiofermal angle (TFA) (Myers, Fishman, McCarthy, Davidson, Gaughan 2005). These angles are calculated by drawing lines along the anatomic axis (that is, parallel to) of the femur and tibia, called mid-diaphyseal lines. There are also lines drawn along the knee joint axis and ankle joint axis. The aLDFA is measured as the angle between the mid-diaphyseal line through the femur with the knee joint axis. The TFA is measured as the angle between the tibial and femoral disphyseal lines, and the aLDTA is measured as the angle between the mid-diaphyseal line through the tibia with the ankle joint axis. Other methods of diagnosis from an X-ray include looking for signs of sclerosis and fragmentation of the tibia.

Prevention
There are several ways that genu varum manifests. The most common manifestation is physiologic genu varum, which is a normal stage of development in children that in most cases requires no treatment, and resolves over the course of the child’s maturation. Genu varum may pose a more serious threat to overall health when it presents in its pathological forms, the most common of which is Blount’s Disease. Because these forms have different causes and require varying degrees of treatment, there are distinct methods for preventing each.

Physiological
Some degree of bow-leggedness is a natural part of the growth process in children. In the majority of cases, this bow-leggedness will resolve on it’s own over the course of the child’s development. It is important to differentiate between benign genu varum, and its pathological counterpart, as unnecessary treatment may actually be harmful to the patient. Typically, physiological bow legs may be present anytime between the ages of 1.5 to 2 years old. There is no need to prevent the onset of genu varum during this time, because it is a natural part of child development.

It is possible that factors over the course of a child’s development may cause their bow-legs to persist beyond this phase, however, and so it is important that they be managed and evaluated. The most prominent risk factor for genu varum is athletic participation, although research has shown that a diet deficient in vitamin D may also pose a risk.

Athletics
The most common cause of physiological genu varum is participation in athletics. Studies have shown that participation in soccer is positively associated with genu varum, as well as numerous other sports.

There are several practices that can help reduce the incidence and severity of genu varum in child athletes, such as participation in multiple sports. In addition to a diverse set of activities involving different types of movement, taking steps to reduce the risk of overuse injuries stemming from athletic participation can reduce the incidence of genu varum.

The American Academy of Pediatrics recommends, among other things:


 * at least one-to-two days of rest from activity each week
 * taking two-to-three months off from a particular sport each year
 * participating on only one team each athletic season
 * focus on good nutrition, proper hydration, and adequate sleep
 * and a robust education of parents, coaches and athletes about the risks of overuse

Pathological
There are several factors that might cause genu varum to persist beyond the range of normal development. Pathological genu varum is most likely to be a result of Blount’s disease. While the early diagnosis of Blount’s disease may mitigate its worst effects, there is no known method to prevent it. There is some discussion as to whether factors such as walking, age, race, weight or gender might present a higher risk of Blount’s disease, but there is currently no definitive proof that any such link exists.

Treatment
Generally, no treatment is required for physiological genu varum for children below two years of age, as it is a normal anatomical variant in young children. Treatment is only needed when genu varum persists beyond approximately two years old and the lower limbs have not naturally aligned, or if caused by disease. In the case of unilateral presentation or progressive worsening of the curvature, when caused by rickets or other diseases, it is advised to treat the constitutional disease first in order to correct angular deformities. Surgical treatment for genu varum caused by rickets is generally not needed for children under two years of age for metaphyseal-diaphyseal angles up to 16 degrees. When the deformity arises in older patients, either from trauma or occupation, the only permanent treatment is surgery, but some non-surgical treatment methods may provide relief.

Non-surgical Treatment Methods
There has been little research on non-surgical treatment methods, but many have tried heel wedges, bracing, and physical therapy. Heel wedges are placed on the lateral side of the heel for bow-legs and on the medial side of the heel for knock-knees. These methods are not effective in correcting angular deformities, but potentially useful for providing comfort and reducing pain.

Guided Growth
Guided growth, also known as hemiepiphysiodesis, is a method of correcting angular deformities in the lower extremities of developing children. This minimally invasive surgical method is useful for gently and gradually aligning the limbs of children whose legs were not naturally corrected in the early years of development (or those with diseases/conditions that led to bowed legs). Guided growth is an attractive course of treatment, especially in growing children, compared to the traditional osteotomy since it is far less surgically invasive, and therefore has less risk of complications. There are multiple methods of guided growth. The most common is inserting an eight-plate (8-plate), a plate with two or more holes and two screws, above the physis of the long bone. This method is considered favorable compared to Blount staples because it avoids damaging the physis in children who are still developing, and it is associated with less complications. Previous to the eight-plate, Blount staples were the main method of temporary hemiepiphysiodesis. It involves placing staples on the medial femoral epiphysis and the medial proximal tibial epiphysis. This is a temporary method because it stops growth, but after the staples are removed, growth resumes. However, the eight-plate method has gained popularity because Blount staples have been known to have several potential complications, including easy extrusion from the bone, implant breakage, physeal damage, and physeal fusion. The screws of the eight-plate method make it more resistant to extrusion from the bone compared to the staples, and is simply more flexible, reducing potential physeal damage. The eight-plate method is also known to have better stability and faster correction of angular deformities since the plate allows for continual physeal growth so that overall bone length is maintained, but growth is not completely halted as it is with Blount staples. Other implants based on similar principles to the eight-plate have been introduced, but the eight-plate and Blount staples are the most common methods of guided growth.

Osteotomy
When a surgical treatment of genu varum is required, a high tibial osteotomy is usually performed, where an incision is made to the tibia and a wedge is either inserted or removed. This procedure realigns the mechanical axis of the leg, reducing the load exerted on the medial compartment of the tibia.

A double level osteotomy may also be performed. In a double level osteotomy, a closing wedge (where a wedge is removed) femoral osteotomy is performed in addition to an opening wedge high tibial osteotomy. Compared to a single high tibial osteotomy, a double level osteotomy allows for finer control, preventing an excessively oblique joint line. However, a double level osteotomy is more difficult to perform, only becoming popular recently with the advent of computer-assisted osteotomies.

Osteotomy is ideally performed before the patient is four years old, after which the rate of complication and the possibility of requiring a repeat osteotomy increases significantly. Regardless, it should be performed as early as possible to avoid heavy degradation to the knee and the need for total knee replacement.

Knee Replacement
Knee replacement may be performed in place of, or in addition to an osteotomy, especially in cases of severe osteoarthritis. Knee replacement can be performed as a total, or partial knee replacement. Total knee replacement is a demanding procedure, with a longer recovery time compared to high tibial osteotomy. A previous osteotomy may also lower the success rate of a knee replacement. Compared to total knee replacement, partial knee replacement is less invasive, and has a shorter recovery time. There is no definitive evidence that knee replacement is better than osteotomy, or vice versa.

Prognosis
Bow leggedness is very common at a young age and in most cases corrects itself naturally by age four. The course of action if this condition persists is to understand what is causing the bowing. The most effective course of action is often one of two different surgeries: guided growth or high tibial osteotomy. These treatments are effective and complication rates have decreased over time. It is important to treat bow leggedness early and treat it while an individual is still growing. Obesity has been linked to increasing arthritis and knee complications. If bow leggedness is not corrected at a young age then over time knees can become weak and arthritis will begin to take its course. Unfortunately, many people with bowed legs will eventually need knee replacement surgery due to the pain and immobility caused by arthritis.

Research
Current research related to genu varum mainly focuses on assessing the effects of orthopedic surgery techniques and other forms of treatment, and understanding the causes. In research studies on treatment and surgery, the surgical procedure or treatment is applied to a patient with genu varum, and the outcomes are assessed. Some studies also focus on the effects of sports, diet, or other health conditions. Findings are typically published in orthopedic, pediatric, or sports medicine journals.