Thread: Bow Legs and Knock Knees

Knock knees and bow legs are relatively common in
infants and children but are usually no cause for concern.
They are stages that children pass through and it
is important to remember that most legs are perfectly
straight by the teenage years.
Bow legs (genu varum)
Bow legs are very common up to the age of three
years. In fact they are quite normal up to the age of
2-3 years. This means that when the ankles are touching
the knees are apart. Bow legs usually correct
themselves when the child starts walking, so much so
that from about the age of four there is a tendency for
the child to develop knock knees.
How can you check progress?
If we are concerned about the extent of the bow legs the
problem can be monitored by measuring the distance
between the knees (DBK). If this is greater than 6cm
and not improving at four years and older it would be
advisable to have them checked by your doctor.
Knock knees
Knock knees are also normal in children and most
have these between the ages of three and eight
years.
The rule for normal three year olds is:
• 50% have 3-5cm between the ankles (DBA).
• 25% have more than 5cm.
These invariably straighten nicely after eight years.
How can you check progress?
For any concerns about the degree of knock knees,
measure the distance between the ankles (DBA). It
should be checked by your doctor if the DBA is
greater than 8cm after the age of eight and not
improving.
Rules in summary
These states are normal:
• Bow legs 0-3 years.
• Knock knees 3-8 years.
• Legs straight by adolescence

What is it?

Bowleg (or genu varum) is a condition where the legs are bowed outwards in the standing position. The bowing usually occurs at or around the knee, so that on standing with the feet together, the knees are far apart.

Knock-knee (or genu valgum) is a condition where the legs are bowed inwards in the standing position. The bowing usually occurs at or around the knee, so that on standing with the knees together, the feet are far apart.


Fig I: Knock-knee (genu valgum) intermalleolar distance
Fig II: Bowleg (genu varum) intercondylar distance


What causes it?

Most people have some degree of bowleg or knock-knee and is considered within the limits of normal structure and function. During development in the first few years of life, because of rapid and differential growth around the knees, most children are bowlegged from birth till age 3, then become knock-kneed till age 5, then straighten up by age 6 or 7. In most children, even as they grow through these phases, the bowleg and knock-knee are not severe, and do not engender concern on the part of the parents. In some instances, the bowleg or knock-knee gets quite obvious, and becomes worrisome for the parents.



Fig: Normal evolution from bowlegs (age 2) to knock-knees (age 3) to normal valgus (age 5)


There are, of course, more serious causes of bowleg and knock-knee. They include the following:
Blount’s disease - a condition of severe bowleg that occurs usually in black children that is progressive, and may require surrgery.
Growth disturbance - or epiphyseal dysplasia, which may be a part of a generalized bone growth disturbance.
Post-trauma - where injury to the knee causes damage to the growth plate (also called the epiphyseal plate) and abnormal growth around the knee.
Rickets. Lack of vitamin D intake, or inability to metabolize Vitamin D due to kidney disease can cause growth disturbance of the bones in the body, including the knee.

What does your doctor do about it?

In the majority of children with bowlegs or knock-knees, the cause is physiological, if they fall within the age range mentioned above. A good rule of thumb to follow is the measure of the intercondylar distance for bowlegs and the intermalleolar distance for knock-knees. In a young child, if the distance is less than 2 inches, there is no need for concern that something is amiss. Periodic observation and measurements are all that is needed.

More detailed work up may be needed under the following circumstances:
If the bowleg or knock-knee appears outside the age range mentioned above, i.e., bowleg beyond age 3 and knock-knee beyond age 7.
If it is unilateral.
If the intercondylar or intermalleolar distance is more than 2 inches, or is rapidly progressing, i.e., more than ½ inch within six months.
Associated symptoms like pain or limp, or signs of Blount’s disease, rickets, or other disease syndromes.


Treatment


Surgery is the only way to change the knee angle -- for braces, shoe inserts and physical therapy are ineffective. Since normal leg development goes from bowlegs to knock-knees, surgery should be postponed until the child is at least 10 years old.

Two bones meet at the knee joint: the femur (thighbone) and the tibia (shinbone). Surgical treatment depends upon the maturity of the child. In younger children, whose growth plates are open and still growing, knee alignment can be changed by tethering the growth plates of the femur or tibia using staples. As the growth plate grows on the untethered side, the knee will grow out of its excessive angle.

In older children, who no longer have open growth plates, treatment consists of cutting, straightening and then holding the bones of the knee in place while they heal with metal implants, including pins, plates and screws.

Although both treatments have high success rates, they should be done only if clearly necessary and at the appropriate age.

Antibiotics
In **EDITED**bow legged adults,certain bone infections such as bacterial infections that result in disfigured bones can be treated with antibiotics.