Medical: Genu varum

English : bowleg, out knee, genu varum


The O-legs are among the axis misalignments. These are deviations from the normal axis. O-legs are characterized by the fact that the axle deviation of the legs is directed laterally outwards. Viewed from the front, the impression of an "O" is created by the deformity.


The O-leg in infancy and neonatal age is part of normal development. If the erection of the body does not occur in the subsequent development period, then the O-shaped legs will remain. However, there is a high rate of spontaneous correction in childhood O-legs.


O-legs can be both innate (see above) and acquired.

Congenital O-legs

At the beginning of every life (until the end of the 2nd year), O-legs are completely normal. Of course, all infants and toddlers have O-legs (Genu varum). However, these develop at the latest in the course of the third year of life and are even tilted in the course of natural skeletal development for some time in the other extreme, to X-legs (genu valgum). Unphysiological X-legs require surgery. From about the age of 10 then the normal leg axis is designed largely finished.

Even with congenital connective tissue weakness or systemic diseases O-legs are present as symptoms.

Acquired O-legs

1. Acquired O-legs can be symptoms of various underlying diseases:

  • Rickets (vitamin D deficiency)
  • hormonal imbalances
  • Bone fragility (osteoporosis) after menopause
  • Overload (for example due to overweight)
  • inflammation
  • tumor
  • Trauma (eg broken bones)

If strong O-legs occur in childhood and persist, rickets are often the cause. Rickets is a disorder of bone growth caused by a lack of vitamin D and calcium. This leads to poor bone mineralization, the growth joints are restructured and it comes to a deformation of the long bones.
In the industrialized countries, a supply of the most important minerals is usually ensured, so that it comes in a balanced diet with plenty of fruits and vegetables, and healthy oils (cold-pressed linseed oil, olive oil) does not lead to a shortage of infants in children. In addition, a moderate stay in the sun (caution, avoid sunburn!) Promotes a sufficient supply of vitamin D.

But other bone diseases than rickets can lead to O-legs. Here come the so-called achondroplasia, osteogenesis imperfecta, but also tumors or accidents (traumas) as possible causes in question. Especially when these influences the growth joints of the bones are affected, there may be a shift in growth, causing the axis "skewed" straightens.

2. Even in paralysis O-legs can arise when the growth direction is changed by an asymmetric muscle.

3. It is also possible that O-legs are completely congenital and one-sided training in adulthood can still cause a subsequent misalignment of the leg axis and thus lead to O-legs.

Some sports favor the formation of O-legs. These are above all sports in which the muscle group of the so-called adductors on the inner side of the thigh during training is more demanding and thus more trained than the outer abductors. For this, the best known example is football. Also, paralysis, which then lead to a muscular dysbalance, can cause the formation of O-legs.


Generally speaking, pain primarily occurs. Due to the misalignment of the legs, there is a constant strain on the knee.
In the case of the O-legs, especially the inside of the knee joints is loaded. This leads to an increased and above all to an early wear of the knee joint on the inner side.
Here, especially the meniscus (esp. The inner meniscus) and the cartilage suffer. Not only in the knee joint problems arise.

Even kink-lowering feet can train. This also serves to compensate, so the compensation, the malposition of the legs. The foot bends outward so that the inside of the foot is too far down. In the clinical examination of the knee joint, tensile and pressure pain, especially of the outer ligament, and typical symptoms of osteoarthritis ( joint effusion, rubbing in the knee joint, movement and stress pain ) can be detected.

If the so-called genu varum is present only on one side, this can lead to a lateral skewing of the spine via a pelvic obliquity in order to compensate for the pelvic obliquity.
Due to these deformities, children must be presented to a doctor (preferably a specialist in orthopedics).

Diagnosis of O-legs

Of course, the diagnosis is made clinically in pronounced forms. Here is from the outside without any problems to recognize the malposition well.
For lighter forms, x-rays may be helpful. Here, the femur and knee joint are x-rayed to the ankle in a so-called axis recording.
To objectively record the extent of the deformation, an imaginary line is drawn from the femoral neck of the femur through the knee joint to the ankle joint.
Normally, this line goes right through the knee joint.
In O-legs this connecting line hits the knee joint too far inside, ie towards the other leg. Another diagnostic option is a run analysis.


Infants and children often have O-legs that "grow together" in development.

The treatment of O-legs is strongly dependent on the age of the patient, as well as their causes and extent of malposition. In infancy, O-legs are normal development. Excessive malformations are often due to disruption of bone growth (rickets) due to lack of vitamin D or calcium intake in the gut. The therapy therefore consists of a high dose of calcium or vitamin D.

Conservative therapy

If the knee deformity is only slightly pronounced, it is possible to treat it conservatively, ie non-surgically. Most custom shoe insoles are used. These are ultimately wedge-shaped elevations of the shoe outer edges, which forces the knee in a tilted-to-center position and thereby the leg axis is straightened altogether. Especially in children, but also in adults, the long-term daily wearing of these insoles promises good therapeutic success. This therapy is often supplemented by physiotherapeutic exercises.

Invasive correction

Since there is a risk of severe and painful long-term damage (signs of wear) of the knee joint, conservative therapy is usually no longer sufficient for more pronounced O-legs ( Genu varum ).

An operative procedure, the so-called Umstellungsosteotomie is necessary to permanently correct the malalignment of the leg axis can. The tibia is severed and the leg is brought into a straight position by the removal of a wedge-shaped piece of bone on the tibia outside or the spreading of the bone end on the inside of the bone. Titanium plates and screws stabilize the tibial bone. The separate bone ends grow together scarless in the next months to years.
A full load of the leg is possible again after about 3 months.

  • O-legs therapy
  • O-leg operation


Unfortunately, in addition to avoiding the underlying diseases or the other triggering factors, the development of the O-legs can not be prevented.


After the surgery usually a hospital stay of about 7 days is scheduled. Partial loading of the bone from the beginning is not only allowed, but also important to strengthen the bone structure.
After 6 weeks at the latest - depending on the X-ray findings - the leg is then fully loaded again. To speed up the healing process and strengthen the leg, physiotherapy should be used. Many patients go about their normal daily routine after about 2 weeks on crutches.

Sport can also be operated by the patients. In the first time, however, not too stressful sports. For example, swimming is an option.

Problems with O-legs

In the long term, all higher-grade leg deformities, whether X-legs or O-legs lead to premature wear of the articular cartilage, so that with increasing age with a gonarthrosis ( knee osteoarthritis) must be expected. In the case of the X-legs, especially the outer knee joint is affected, while in the case of O-legs an internal knee osteoarthritis comes into play.
However, the extent of osteoarthritis depends on other risk factors such as obesity, connective tissue weakness, accident and injuries, etc.

O-legs in babies

As the child grows, his lower extremities undergo some development. Already at birth, but at the latest at the beginning of walking, every child shows an O-shape of the legs ( Genu varum ). Over the next few years (usually up to the third year of life), this will balance out and the legs take on a straight shape ( genu rectum ), as found in healthy adults. During the following years, however, the previously found "malposition" of the O-legs will reverse to the opposite, it will form X-legs ( genu valgum ). These in turn will disappear until about the age of 10, so that the child should have a straight leg axis until puberty.

In contrast, very pronounced or increasing O-legs in neonatal and infancy are in need of observation. In most cases, however, this deformity is benign and over the years. Nevertheless, it can be helpful if you document the development of your child's legs with photos, so that the treating pediatrician can always understand the development well.

O-legs in adulthood

Uncorrected malpositions of the joints can lead in the long run to partially serious complaints. Since the inner parts of the knee joints, or more precisely the inner thigh rolling hills, are more heavily loaded in the case of O-legs than the outer ones, they increasingly wear over the years. This promotes the development of osteoarthritis, in this particular case of knee osteoarthritis (internal gonarthrosis), which then comes into play at the latest in old age. At the beginning of this disease are pains in the neck and a recurrent inflammatory activations of gonarthrosis. The already existing malposition of the knee will be further increased as a result of the increasing wear of the inner articular surface and may take on grotesque forms in old age.


O - legs are deviations of the normal straight leg axis to the side outside. O-legs can be both innate and acquired. Especially in newborns and infants, O-legs are completely normal and spontaneously return.
Among other things, trauma can be acquired. Symptoms include pain, which is usually caused by osteoarthritis and uneven wear on the knee joint. If the O-leg occurs only on one side, the spinal column may also develop as a compensation, which the body wants to accomplish.
The therapy is based on the causes and can range from the treatment of the underlying disease to the operation. Depending on the severity of the disease, it is ultimately necessary to resort to the method of surgical therapy. These cases are associated with a good prognosis.
However, patients must strictly adhere to the physician's instructions regarding the allowable load.

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