Straight” legs are normal, although not all children have completely straight legs. We say that they have genu valgum when the knees come together and the feet are separated, with an “X” shape.
The genu valgum is an abnormal distribution of loads on the knee and the alteration of the kinematics of the patella, which could end in osteoarthritis.
What are the causes?
From the age of 1.5-2 years, children’s legs begin to “deform” in valgus, it is a physiological process (the medical reference for “normal”). They reach the maximum of valgus at 3 years of age, and from that moment on, as they grow, they become straight. A minimum of deviation compared to the “straight” position is normal.
However, cases of idiopathic genu valgum occur when genu valgum persists above certain standards and upon reaching adolescence can no longer be corrected on its own.
We also have cases of genu valgum secondary to metabolic pathology, congenital and as a consequence of fractures.
How and when is it diagnosed?
In the office we use as a clinical measurement the distance between the two ankles in standing position and with the knees together. Another way is to measure the angle between the thigh and the leg (between femur and tibia), which is relatively easy nowadays with angle measurement apps.
If it goes beyond a physiological range and we consider the possibility of needing correction, we do an X-ray of the legs.
This is a special X-ray that is done by overlapping images of a front X-ray of the hips, knees and ankles with the patient standing. The mechanical axis of the extremity, the deformity corresponding to the femur and the deformity corresponding to the tibia are measured on this X-ray.
What treatment is carried out and how is it corrected?
We consider correcting it when it exceeds the “normal” deviation and may pose a mechanical problem for the knee. Depending on how far the axis passes from the center of the knee, we will consider more or less the need for correction. We divide the area through which the axis of the knee passes into I, II and III. The III are operated, the I are not and the II are evaluated individually.
For the correction the orthoses are NOT valid. The use of insoles or special boots for genu valgum correction are not supported by current science.
In children we can guide their growth. Just as brackets on the teeth are placed over the months, the “brackets” that we put on the knee are putting it straight within 10-18 months, depending on the magnitude of the deformity and speed of growth. This technique can be performed reversibly (hemiepiphysiodesis plates) or irreversibly (definitive hemiepiphysiodesis).
In mature patients, where the remaining growth does not allow guided growth techniques, it is necessary to perform a somewhat larger corrective surgery by means of an osteotomy (cutting the bone, turning it into place and fixing it with plate and screws). It is frankly much more messy than doing guided growth, so it is better to correct this in pre-adolescence, around the growth spurt.
What guidelines should we follow if we are diagnosed?
Diagnosis at an early age, around 3 years of age, is not a cause for concern as it is part of the physiological development of the child. We will pay attention to the fact that it decreases during childhood until pre-adolescence.
If there is no associated deformity in the ankles or feet, the use of insoles will not be necessary. Overweight seems to be related to the increase of genu valgum, so it will be another factor to control.
We should consult a specialist in pediatric traumatology when a preadolescent maintains a still striking genu valgum, at around 10 years of age in females and 12 years of age in males. This would allow for follow-up and possible surgery in females at around 12 and males at around 14 years of age.