Children’s knees bending inward (commonly known as O-shaped legs) or turning outward (commonly known as X-shaped legs) are quite common and annoying to parents, as are inward and outward-facing feet. When they see that their child’s legs are bent and different from other children’s, parents are most worried: Is this normal? Will it get better in the future? If not, how ugly it will be! Should we correct it in time so as not to miss the opportunity of treatment?
Most of the infant’s calves are inwardly curved. To distinguish between normal and abnormal, we should first understand the normal process of lower limb development in children. Before birth, the fetus is flexed in a narrow space in the womb, and the lower limbs, especially the lower legs, are quite inwardly curved. Therefore, nine out of ten newborn babies have inwardly curved and internally rotated calves. First-time parents are often puzzled by this, mistaking it for something abnormal and asking for treatment, which is unnecessary. The inward bending of the knee becomes more apparent when the child begins to walk. When children land on their feet, most of them have a combination of inwardly curved feet that look as if a ball could pass through the middle of their legs. In fact, when the child is lying down for examination, both lower extremities still look bent, and the “O” leg is especially obvious when walking. This is also the time when parents often bring their children to the clinic. In fact, inward curvature is a normal physiological phenomenon around 1.5 years old. At the age of 2, the lower extremities gradually straighten out, and then the knees begin to turn outward and the bones on the inside of the knee appear to bulge, especially in tall, thin children. at the age of 3, this “X” shaped leg reaches its most severe level, and when standing, if the knees are leaning, the feet are spread apart and cannot close. It is very difficult to see when running, and the knees will touch each other internally and trip over themselves. At this stage, it is not uncommon for children to be brought to an orthopedic surgeon. Parents are worried that if they don’t look good in the future, they will have problems in the military because they may not even be able to stand upright! Fortunately, this situation will improve after the age of 4-5 years old, and as they grow, they will show a slight outward bend like adults. So, physiologically, children’s knees go through the normal process of inversion, straightness, valgus, and slightly valgus.
Ligamentous laxity in bent legs will improve as they grow, so why do some children’s legs bend more than others? Most of them can be said to be normal differences, just like people’s height and weight, not everyone is the same. The second is laxity of the ligaments. We know that the ligaments are loose in children just after birth, so they can very gently put their toes in their mouths, bend their bunions to touch their forearms or fold their fingers back to be parallel to their forearms. When lying down, the feet appear to be fairly straight and have arches, but when standing, the knees are bent inward or backward and the phenomenon of flat feet is present, and the phenomenon of “O”-shaped legs is more obvious when walking. The ligaments are slightly looser than those of people with straight legs. Generally speaking, ligament laxity is a physical factor that improves with growth, and only about 4-7% of people still have ligament laxity in adulthood, as we can see from the simple tests mentioned above. Also, some ligament laxity is hereditary, and it is less likely to improve in this group of people. Some people blame diapering or early learning to walk for their children’s bent legs, but we don’t think diapering has anything to do with it.
Calcium or vitamin D deficiency can also bend the legs. A few cases of entropion (X-shaped legs) are caused by disease. We should be suspicious if: (1) The bend in the leg does not match the age: for example, the leg turns outward after 1 year of age, or the leg still turns inward after 2 years of age.
(2) Legs bent especially: Although the direction of the leg bend is consistent with age, but if the excessive bend, we should be suspicious.
(3) asymmetry: that is, only unilateral bending or two legs bending degree, direction is not the same, there must be a big problem. Disease causing leg curvature. The most common is rickets caused by calcium or vitamin D deficiency. This type of child often only eats mother’s milk until about 1 year old, and rarely eats side dishes, cow’s milk or supplements, so they also look unhealthy in appearance. In addition to the legs bending inward, the bony ends also appear to be extraordinarily elevated. There are even multiple bulges at the junction of the rib cartilage in the chest.
In addition, congenital skeletal abnormalities such as dwarfism are often combined with bending deformities of the lower extremities, which are not a problem to identify because the height, upper body, and extremities are abnormal. Rickets can also be caused by congenital abnormalities in calcium and phosphorus metabolism (e.g., hereditary hypophosphatemia) or by acquired kidney disease. The former often has a family history, and the latter is a chronic kidney disease that should not be difficult to diagnose. Acquired factors also include fractures and sequelae of inflammation, osteomas, or bone abnormalities. There is also a disease called “Bronte’s” disease, inversion of both knees is more serious than the average child, is a tibia (calf bone) on the inner bone growth disorder, the cause is still not understood, generally thought to be related to the child is too fat or too early walking. The differential diagnosis between normal and abnormal leg curvature is not difficult, as already mentioned above, with age, family history, and detailed physical examination, more than 90% of people are normal. It is only when pathological factors are suspected that we ask the patient to take x-rays or blood and urine tests. Patients with rickets can see the widening of epiphysis and poor calcification on X-ray, and other diseases also have their special X-ray and blood changes. However, from a biomechanical point of view, a bent knee that persists into adulthood can lead to knee osteoarthritis due to uneven forces. Generally speaking, we do not encourage children to learn to walk too early and not to eat too much, because if children have already learned to walk, it is impossible to prohibit it.