Genu valgum (knock-knee)
Genu valgum is another common normal variant of alignment in children that typically corrects itself with normal growth. While standing, the legs are angled inward so that the knees come close to each other and the ankles are farther apart. The deformity most commonly comes from the femur. Knock knees are most exaggerated in toddlers aged between 2 and 4 years. Genu valgum is considered a normal variant of alignment (physiologic knock knee) until age 7 years. Up to 75% of children aged 3 to 5 years have knock knees, and up to 95% of these children will self-resolve by age 7 years.15
On physical examination, the intermalleolar distance can be measured with the knees approximated; up to 8 cm between the ankles is normal. Make sure to assess thigh-foot angle and hip rotational profile, as the same appearance can be attributed to a combination of increased femoral anteversion and external tibial torsion. Surgical treatment is quite rare, but is considered for severe progressive deformity. Guided growth technique and osteotomy are surgical options.
Genu varum (bowed legs)
Curving of the legs in which the knees are far apart is termed genu varum. In the first 12 months of life, bowed legs are physiologic. They begin to straighten as the child grows. Genu varum typically improves by about age 18 months, but in many children, it persists a little longer. Ninety-five percent of children with bowed legs will improve by age 4 years with normal growth.15
On examination, the legs should appear symmetric and the bowing should appear smooth/gradual along the leg versus an abrupt angular change. Standing intercondylar distance can be measured with the feet together; up to 6 cm is considered normal.6
If a child also has ITT, the ITT can complicate matters by making the bowing appear worse than it really is because the side of the knee is visible relative to the foot rather than the front. Fortunately, both conditions typically improve around the same age with normal growth.
For physiologic bowing, the treatment is generally observation. Special devices/shoes typically are not needed. However, bracing and/or surgery may be indicated for pathologic genu varum because of conditions such as rickets or Blount disease.
Pes planus (flatfoot)
Flexible flatfoot is a normal variant that is often familial and secondary to ligamentous laxity across the arch. Early on, parents can be reassured that almost all babies have flat feet. There is a medial plantar fat pad that obscures the arch from birth. More than 40% of children aged 3 to 6 years have flat feet. About 1 in 7 people have flat feet as adults (roughly 14%).6 Arch development can continue up to age 8 years as the muscles and ligaments in the arch mature and tighten.
Physical examination should be done with and without weight bearing. With the child seated and legs hanging from the exam table, the arch is typically revealed without bearing weight. The Jack toe raise test—passive dorsiflexion/extension of the great toe—can also be done to emphasize a flexible arch. During weight bearing, the arch will flatten but reappears when the child stands on his/her tiptoes. These maneuvers help distinguish flexible flatfoot from rigid flatfoot. Rigid flatfoot warrants further workup, including imaging to rule out other conditions such as tarsal coalition or congenital vertical talus.
Observation is typically recommended in children aged 8 years and younger, as the arch is still developing and symptoms are rare before age 8 years. Occasionally, however, pain can flare with activity or children can have difficulty with shoe wear. Research has shown that the use of orthotics, shoe inserts, special shoes, or exercises do not stimulate arch development. However, they can provide support and comfort. Reconstructive surgery is reserved for the rare severe cases that do not respond to conservative treatment.
Pronation is a normal foot motion that refers to the action of the foot as weight is applied through the gait cycle. Essentially, the heel and ankle roll inward after the heel strikes the ground, and as weight is transferred to the midfoot, the arch flattens out. Pronation is normal; however, problems can arise when there is overpronation. This places increased stress on the muscles and ligaments of the foot. Treatment is almost always nonsurgical.
Careful clinical evaluation can determine if the child is having pain or if pronation is affecting the overall limb alignment. A first step can often be trying an over-the-counter arch supports to provide better foot support, improve alignment, and decrease premature shoe wear/tear. Ankle braces can be used during sports to give additional support.
Variations in the lower limb appearance can raise concern among parents and clinical providers. Whereas the majority of rotational and angular issues are benign in children, recognition of the classic clinical presentations is important in order to diagnose quickly and correctly and initiate further workup when indicated.
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