Presented by: Jeffrey Young, MD
Clinical Assistant Professor, Orthopedic Surgery
Stanford University Medical Center
March 20, 2014
For many children, growth of the lower limbs does not always follow the straight and narrow. Children can have temporary deformities like bowlegs, knock knees, in-toeing (pigeon toes), and out-toeing, especially in their early years. “A deformity is anything that doesn’t conform to normal or expected shape,” said Jeffrey Young, MD, a clinical assistant professor of orthopedic surgery, who spoke at a presentation sponsored by the Stanford Hospital Health Library. “Some of these conditions correct themselves without treatment over time. Many are just normal variations of human anatomy.”
Bow Legs and Knock Knees
If your child stands with his toes forward and his ankles together but his knees don’t touch, he’s bowlegged. If his knees touch but his ankles don’t, he’s knock-kneed (genu valgum). These conditions are known as frontal plane deformities because they are visible from the front.
An X-ray is can be taken to determine the extent of the condition. The knees are positioned directly forward. A static image is taken of the hips, knees, and ankles and a line is drawn to assess the alignment and to determine the extent of the deformity and its progression over time.
In most children under age 2, bowing of the legs is simply a normal variation in leg appearance and is referred to as physiologic genu varum. The bowing begins to slowly improve at about 18 months; by about age 3 or 4, the legs can develop a knock knees appearance and is referred to as physiologic genu valgum. By about age 8, the legs will typically have their adult appearance.. Bow legs usually show up at an early age—up to age 2— and knock knees appear later, at around age 3 to 5 years.
“Kids change gradually over time,” said Dr. Young. “But in some cases, the change can be substantial and definite.”
Bones grow from the end, which is known as the growth plate, or physis. The physis is made out of cartilage, which is weaker than bone, and allows the bone to lengthen and grow. Genetic or external forces can cause the growth plate to grow unevenly. Also trauma, fracture, or infection can sometimes affect the bone’s growth plate, so that the bones grow asymmetrically. Deformities also can stem from a metabolic bone disease like rickets, caused by a lack of vitamin D, or Blount’s disease, a growth disorder associated with obesity that affects the bones of the lower leg, causing them to bow outward. Some children are born missing the fibula, one of the lower leg bones, which can lead to knock knees.
Generally, initial treatment involves careful observation and tracking changes over a period of time.
“You don’t want to act too quickly on something that may get better on its own,” said Dr. Young, who treats children, adolescents, and adults with conditions carried over from childhood. “There’s no real reason to be too aggressive, especially in young children. But if treatment is needed, it should be done by puberty, while the bones are still growing.”
Bracing used to be a common approach. Most physicians these days are skeptical that it is necessary, although it appears to be helpful in cases of Blount’s disease affecting very young children.
Hemiepiphysiodesis is a surgical procedure aimed at slowing growth on one side of the growth plate so that continued growth on the other side will straighten out the limb. A tether is held in place on one side with small plates and screws as the bone continues to grow. This approach is best while the child is still growing, and in fact, can show rapid results during a child’s sporadic growth spurts, Dr. Young said.
A more drastic approach is required after the bones are fully developed, usually by the mid- to late-teenage years, by a procedure known as an osteotomy, in which the bone is cut, straightened, and allowed to heal in a new position. Internal and external hardware can be used to keep the bone in place during the healing process.
In-Toeing and Out-Toeing
Extreme angles of the feet pointing in in or out are called transverse plane deformities because they can viewed from above. Young kids with pigeon toes often trip, but in time this usually improves. Out-toers might be slow runners, as the angle can alter the biomechanics of the feet.
Children often grow out of these conditions over time, and there is a wide variance of what is considered “normal.” Compensating for these angles occurs, but it is uncertain if this actually causes any orthopedic problems as an adult.
“The goal in these conditions to isolate where they are coming from,” said Dr. Young. “What is twisted? It could be the foot, the leg, or the thigh.”
A thorough physical exam is the primary means of diagnosing the cause of in-toeing or out-toeing. In-toeing can be caused by faulty alignment in the foot (metatarsus adductus), a twisted shin (tibial torsion), or a twisted thighbone (femoral anteversion).
The first step is to use a heel bisector to measure the angle of twist in the foot; a normal measurement falls between the second and third toes. If the line falls close to the fifth toe, it might be an indication of metatarsus adductus.
The exam will then measure the angle between the thigh and foot to determine the twist of the shin bone. Comparing the degree of internal and external twist in the thighs helps determine the twist of the thigh bone. These measurements make up the rotational profile of the legs. An internal twist in the feet with an external twist in the thighs is a common position in newborns. Both an internal tibial rotation and an external femoral rotation generally improve on their own. The foot progression angle—the angle of the footsteps—can vary by as much as 30 degrees in either direction.
“These deformities also change over time,” Dr. Young said. “The change is very slow but steady, and the range of ‘normal’ is quite broad.”
A more thorough assessment is done using motion and gait analysis in a special lab. The test uses mathematics and 3-D imaging to analyze how a patient walks and may help to identify abnormal walking patterns. “You get a dynamic sense of what’s going on,” he said.
Treatment for in-toeing and out-toeing is limited, and usually involves either observation or surgery with very few options in between. Osteotomy procedures will cut the bone and lock it in place using pins or a metal plate.
There are some other situations that can affect a child’s stance that require more immediate attention, said Dr. Young. Hip dysplasia, a dislocation of the hip, can lead to early hip arthritis if left untreated.
Slipped capital femoral epiphysis, or SCFE, occurs when the ball at the upper end of the thigh bone to separates from the main part of the bone. It usually arises during the growth spurt of adolescence, leading to hip or knee pain and a limp. It’s often treated by holding the bone in place with an internal screw.
Miserable malalignment syndrome causes knee pain because the thighbones are twisted internally and the shin bones are twisted externally. A child who tends to sit in a W position, with the knees facing in and the feet splayed behind, might exacerbate the problem and should be gently discouraged, advised Dr. Young.
About the Speaker
Jeffrey Young, MD, is a clinical assistant professor in the Department of Orthopedic Surgery. He received his MD from the University of Pennsylvania, and did a residency in orthopedics at McGaw Medical Center of Northwestern University in Chicago. He completed a fellowship in limb lengthening and reconstruction at the Sinai Hospital of Baltimore and in pediatric orthopedics at Royal Children’s Hospital in Melbourne, Australia. He has volunteered his expertise on surgical missions to Haiti, Columbia, Nicaragua, and Guatemala. He joined the Stanford faculty in 2011.
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