There are two possible causes for a malposition of the legs. The bow leg (genu valgum) and the bow leg (genu varum). Both malpositions are usually congenital, but can also be caused by crooked feet (flat feet).
In this case, the feet sink inwards and the growth of the legs is impaired due to the incorrect loading. A lack of vitamin D also causes a defective position of the legs. This is caused by a disease called rickets.
If vitamin D is missing, the important bone substances calcium and phosphate cannot be properly absorbed, the bones soften and are no longer able to bear the increasing body weight during growth. This results in malpositions of the hip joint or knee joints. However, rickets are very rare nowadays.
Other reasons for malpositioning of the legs include hormone disorders, tumours or overweight. Traumatic causes, such as broken bones or injuries to the growth joints, cause leg malpositions especially when they occur in childhood or adolescence, i.e. when the body is still growing. Symptomatic for knock-knees or bow legs is the quickly visible deviation of the legs from the normal body axis.
A leg is considered straight when the axis (carrying axis) runs straight through the femoral head of the hip joint, the knee and the ankle joint. With the bowleg, the knee deviates inwards from this imaginary axis, with the bowleg it deviates outwards. Further symptoms of a leg malposition only appear as late effects.
For example, wear and tear of the knee joint (gonarthrosis) occurs due to the one-sided load. In the knock-knee, the inner parts of the knee joint wear out first; in the bowleg, the outer parts are affected earlier. The arthrosis then results in pain, especially under load, because the joint surfaces no longer slide optimally over each other. In addition to arthrosis, meniscus damage or bone edema play a role as symptoms.
Leg straightening for children
If the leg malposition is to be corrected in children who are still growing, a splint that must be worn at night can be used to counteract the incorrect growth. Elevated insoles on the inner side of the foot can help against buckling flat feet, which are considered the cause of bow legs. These are adapted to this and should be worn in shoes as often as possible.
In addition, special physiotherapeutic gymnastics exercises can be used to compensate for the defective position of the leg and thus counteract possible late effects such as arthrosis. However, if the malposition is pronounced, or if the above-mentioned measures do not work, there is also the possibility for children to straighten the axial deviation surgically. If it is necessary to straighten children’s legs, the so-called epiphyseodesis is used.
The epiphysis (growth plate) is injured on one or both sides. However, only unilateral epiphyseodesis is used to correct knock-knees or bow legs. Unilateral epiphyseodesis serves to control growth and is usually reversible, i.e. it can be reversed.
There are two possibilities for reversible epiphysis. On the one hand, the growth plate can be penetrated so that the growth stagnates for the time being. However, the injury to the joint caused by the penetration, usually caused by a screw or wire, heals and growth continues.
Alternatively, it is also possible to “bridge” the growth joint from the outside and thus temporarily inhibit growth by means of staples or plates. An epiphysiodesis is a massive intervention in the natural growth of the body. Thus, it sometimes happens that growth stops even after removal of the screws, plates or wires.
Excessive or asymmetrical growth has also been described as an after-effect of such an intervention. Especially the latter must be avoided if possible, because the intervention should prevent asymmetric growth, not cause it. Implants placed in the growth groove can also loosen and slip and then affect surrounding structures.
For example, nerve damage or injuries to the periosteum (periosteum) can occur. In very rare cases, temporary manipulation of the growth plate can result in the formation of small bone bridges, which can lead to a permanent stop in growth. Whether or not an epiphysiodesis is really performed on a child should therefore be decided individually in each case. If the deformity can be compensated for by other means, or if it is not very pronounced, one should carefully consider whether an operation is really necessary, because all operations mean great stress for children and should be avoided if possible.
