Many of us have seen a lot of children with knock knees or bowed legs, however, parents do not have an idea if this lies within a normal range or not. In this article, I will try to answer how much varus or valgus is normal, at what stage do you need to see pediatric orthopedics.
First things first, the word genu means knee and valgum denote the position where feet are placed away and the knee is placed closer, to each other. In common words we call this deformity as knock knees when the reverse happens, it is called genu varum or bowed legs.
When the child is born, there is varum at the knee joint. However, this becomes neutral at around 18 months of age which then progresses to valgum, till the angle between the thigh and legs (Valgus Angle) reaches a maximum of 15 deg at the age of 4 years. After that, it starts decreasing and finally stabilizing at 7 deg, which is the normal range after 7 years of age. This growth pattern is based on the salenius curve, so anything that does not follow the curve comes under abnormal. In other words, this becomes, pathological genu valgum/varum.
The cosmetically unappealing appearance of the knee is the most common reason that compels the concerned parents to bring their kids to us. Sometimes, there is a history of repeated falls while playing due to problems in balancing. Most of the children come under a normal pattern of growth except a few who need constant supervision and may require surgery.
Why does deformity occur?
The deformity happens due to differential growth of both the sides of the knee joint, which means that if more growth happens in bones around the knee joint on the inner side, the leg will go into valgus and vice versa. This can happen in case of traumatic injury, metabolic disorders like rickets, dysplasias, physical injuries. As far as treatment is concerned, we follow the guided growth principles, whereby, we reduce the side which is growing fast so that the other side catches up and thereby leading to correction of the deformity. This procedure is called Hemiepiphysiodesis. It is a very simple procedure with minimal incision. But the catch is that the child needs to be of growing age. Normally the growth takes place until 16 years in girls and 18 years in boys. The children need to be reviewed periodically to make sure that the deformity does not recur. If the child has completed the growth, the only option left is to cut the deformed bone and to realign it and fix it, we call that osteotomy.
The take-home message is that most of the knee deformities are asymptomatic that need medical supervision only except for a few ones which need surgical intervention. And in those knees, the timing of surgical intervention becomes crucial because the deformity can be managed easily when the problem is detected at a younger age. Hence, whenever, there is a doubt, consult pediatric orthopedics as soon as possible.