Dr. Sam Hassan from Mediclinic sheds some light on what bow leg is, and what it means as your child grows.
Usually babies stand for the first time at the age of around nine to 10 months and they walk by the age of 13 to 16 months. These milestones of standing and walking are happening progressively and not without normal variation between children. There are two important (normal) physiological developments however, which might lead to excessive concerns for parents; Genu Varum (Bow leg) and Genu Valgum (Knock knees). Although both are part of normal development, some conditions may lead to problems.
Babies are normally born with bow legs but it is more noticeable when they start to stand and walk. Around the age of 1.5 to 2 years the legs become straighter, however they change into knock knees around the age of 3 years, before they become straight at the age of 6 to 7 years. These changes are normal and more obvious in overweight children. They are different from other normal conditions of in toeing and out toeing.
In normal developmental bow legs, the distance between the knees while the child is standing or lying is not more than 5 to 6 cm, while the normal distance between the ankles of feet in knock knees is less than 5 to 6 cm. Signs of problems arise if the distance in both conditions is more than 7 cm and 10 cm at the ages of 3 years and older. These distances are usually measured when your child is assessed by a specialist doctor to make sure that in the follow up that they reduce and not increase. Parents themselves, if concerned, may take photos at different ages of the knee of the child while standing in the same way in order to notice the improvement in the knees or not. Photos can be taken every three months in order to see any changes.
Usually and if the measurements are normal there’s no need for further tests, however if the specialist is concerned, then knee and hip X Rays might be required. This is required for rare conditions only and in all circumstances risks have to be weighed against benefits for any radiological or blood tests in children. In the past doctors used to see many cases of vitamin D deficiency leading to rickets but this is very rare today due to the addition of vitamin D to milk and supplements to breastfed babies. However, although vitamin D deficiency is very common it is rarely the cause of leg deformities. In fact recent research in medicine showed that vitamin D is a very important element in many physiological and immunological conditions. Vitamin D deficiency may lead to recurrent respiratory infection similar to asthma, affect the status of blood glucose and diabetic control, reduce the immune system function, cause leg pains and tiredness, may affect the concentration and the cognitive abilities and many other functions.
Children with normal bow legs or knock knees need no treatment as this is a natural development. There is no evidence that special shoes or splints or other supports are of any help. However, if there are any associated conditions with it, such as hypermobile joints or flat feet or excessive out and in toeing then special boots may be advised as well as physiotherapy. There is one condition called Blount’s disease which can cause bow legs and it generated by a defect in the growth of the tibia bone. In this condition, the bow legs usually get worse with time. It is also known to cause asymmetrical bow legs and happen more quickly and progress more rapidly. Usually the knee x ray can show the Blount’s disease by the age of three. Children with Blount’s disease are usually referred to the paediatric orthopaedic doctors to treat them with braces initially. If not effective, surgery may be required.
Other rare causes of bow legs are fractures, abnormal bone development and very rarely fluoride and lead poisoning.
If you are concerned about excessive bow legs or knock knees it is better to get your child assessed yet bear in mind that the commonest cause is only normal development and treatment of further investigation is rarely necessary. Only a few cases require special attention and this should be decided by clinicians.