Knockinâ€™ Knees and Bowinâ€™ Legs (and when theyâ€™re okay)
One of the most common questions I am asked by parents is about their child’s knees. Parents bring their child or adolescent into the office concerned with the fact that they are either “knock-kneed” or “bow-legged”. “Is this normal?” they ask with a worried expression on their face. The vast majority of the time I am able to reassure them that the funny angulation of their child’s legs is just a natural part of development. I am asked about this often enough that I thought it warranted a formal blog explanation of when these two conditions are okay and when they deserve further investigation.
Knock-knee, known to the medical community as genu valgum, is a condition when the knees are angled in and touch each other when the legs are straightened. The feet may not be able to touch. This is seen as a normal occurrence in children ages 3-5 and may persist as late as age 8. There is also a second normal episode from ages 12-14. Outside of these age ranges the knees usually straighten up.
Persistent knock-knee can be the result of obesity (most commonly), Rickets (deficiency of Vitamin D, calcium, or phosphate), or an injury to the growth plate in the leg. Over time abnormal genu valgum can lead to problems in the developing foot as well as early onset knee osteoarthritis.
The opposite of knock-knee is bow-leg, known as genu varum in the medical community. In this condition the legs bow outward in relation to the thigh. This is normally seen at birth and can continue for the first 4 years of life. We also believe that chubby babies who walk early (at about 9 months) have bowed legs because of the weight and stress being put on the leg bones which are still partially soft cartilage at this age.
Genu varum, like genu valgum, may be caused by Rickets. Another disease process that should be considered, especially in the case of bowing of only one leg, is Blount’s disease. Blount’s disease is caused by growth arrest of the inside portion of the growth plate just below the knee. The outside of the leg continues to grow but the inside doesn’t. There are two forms of Blount’s, one occurring in infancy and one in adolescence. Bowed legs, like knock-knees can also be cause by traumatic injury to the growth plate of the leg. In adults bowed legs are often seen in certain occupations like jockeys and rodeo cowboys.
As a physician, if I see a patient that I believe has abnormal knock-knees or bowed legs I take a detailed medical history and do a physical exam, taking measurements of the legs. I also get x-rays of both legs and take measurements from them. Both Blount’s disease and Rickets have specific characteristics on x-ray. Also a child with Rickets will appear weak and may have other skeletal abnormalities as well.
In the case of Rickets the first line of treatment should be correction of the underlying deficiency. In a young child with bowed legs, treatment can be as simple as bracing. In persistent cases of either deformity, surgical treatment may be warranted for permanent correction.
I hope this short explanation of these two conditions proves useful. If I help even one parent not lose sleep over their child’s bow-legged appearance then I have done my job. Or at lease saved someone an office visit co-pay J. As always, if you have any further questions or would like your child to be evaluated by a doctor for either of these conditions, at Advanced Foot and Ankle Care we have four willing and able doctors at four convenient locations to meet your needs!