7 lower limb positional variations

Although many issues related to walking are benign, early recognition of these classic clinical presentations is essential for initiating further workup when indicated.

“Is it normal for my child to walk like that?” “Are my daughter’s legs supposed to turn in that way?” Concerns regarding the appearance of a child’s lower extremities are a common reason for visits to the pediatrician and a frequent source of orthopedic referrals.¹ Musculoskeletal exam findings change as a child grows and develops. It is crucial for the pediatric clinician to be able to recognize normal pediatric orthopedic variants in order to differentiate conditions that can be treated with reassurance and education from those warranting further evaluation and workup. The aim of this article is to provide guidance on the diagnosis and management of 7 common lower limb positional variations in children and adolescents (Table).

Evaluation

Accurate diagnosis of rotational and angular problems starts with a detailed history. Is there a family history of pediatric orthopedic or neurologic issues? Does the limb appearance or the way the child walks resemble anyone else in the family? Oftentimes, a sibling walked the same way or a parent will describe having bowed legs or knock knees as a child but outgrew it. How long has this been a concern, and does it seem to be improving or worsening over time? Are there any systemic signs such as fever or fatigue? Ask about pain, falls, and tripping. Inquire about underlying nutritional issues, growth concerns, developmental delay, and history of injury.² These can be red flags of something other than a normal variant.

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Physical examination includes a generalized musculoskeletal examination, and should always include observation of gait and rotational profiles of the legs.3 Key assessment points are: 1) foot progression angle; 2) internal and external rotation of the hips; 3) thigh-foot angle; 4) heel bisector; and 5) limb position and arch appearance while standing in bare feet.

The foot progression angle (FPA) describes the inward or outward position of the foot relative to the direction of ambulation. Watch the child walk. Focus on 1 foot at a time and observe them walking toward you as well as walking away from you. Inward FPA is quantified in negative degrees (ie, internal tibial torsion [ITT] has an FPA more negative than -10°) or outward (positive value). Normal FPA ranges from -5° to +15°.⁴ Slight out-toed gait is most common. Keep in mind that FPA does not identify the source of limb rotation, however, it helps quantify severity and can be monitored for change.

Rotational profile of the lower limbs is best assessed with the patient in the prone position with the pelvis flat to the table. Internal rotation, external rotation, and thigh-foot angle should be evaluated. Internal rotation increases over childhood, peaking in mid-childhood at ages 6 to 8 years.⁴ This explains the normal variant of femoral anteversion during that time. External rotation is greatest in the newborn and then declines rapidly. This also explains the common finding of outtoeing in infants/toddlers.

Thigh-foot angle (TFA) compares the axis of the thigh with the axis of the foot (heel bisector). With the patient prone and knees flexed to 90°, the ankle is put into a natural position. If the foot points outward, the angle is positive, and if it points inward, the angle is considered negative-just as is done with the foot progression angle. A thigh-foot angle that is inward at least -10° is consistent with internal tibial torsion.³

Examination should include inspection of the lower limbs and feet both at rest and during motion. While seated, the heel bisector can be determined by drawing a line through the mid-heel up through the forefoot. A normal heel bisector should go between toes 2 and 3. Metatarsus adductus will present with a heel bisector that extends more laterally through toes 3, 4, or 5, and the lateral border of the foot will be convex rather than straight.

Red flags include an asymmetrical deformity, leg length discrepancy, limitation in joint movement, tenderness, pain with range of motion, and short stature (<25th percentile).⁵ In these situations, consider further evaluation including but not limited to radiographs and lab work (calcium, vitamin D, alkaline phosphatase, phosphorus, for example).

NEXT: Intoeing

Intoeing

Intoeing gait is the most common parental concern regarding how children walk. Nearly 2 in 1000 children have intoeing gait and it is typically bilateral.⁶ The 3 most common reasons for intoeing are metatarsus adductus, internal tibial torsion, and femoral anteversion. The conditions classically present in that order: metatarsus adductus in an infant, internal tibial torsion in a toddler, and femoral anteversion is seen most commonly in a school-aged patient.

Metatarsus adductus

Metatarsus adductus (MA) is a typically flexible deformation that is believed to occur from intrauterine positioning. It occurs in 1 in 5000 births and is more common in males, twins, and preterm babies.⁷ There is medial deviation of the forefoot relative to the hindfoot, resulting in a curved foot appearance. The heel bisector will be at the 3rd toe or more lateral. The majority of children improve on their own. More than 90% of children diagnosed before age 1 will self-resolve.^8,9

Management depends on whether the adductus is flexible or rigid. Flexible MA is either actively correctable (the child can make his/her foot point straight) or passively correctable (foot can be stretched to/past neutral by the clinician). Flexible MA is typically managed with observation, gentle stretching, and reassurance. It is best to stretch multiple times/day, such as with each diaper changing or feeding. In some cases, children with flexible MA can benefit from treatment with bracing, orthopedic footwear, or serial casting to more aggressively improve flexibility and position at rest.

Families can be reassured that surgery to straighten the foot is seldom required. Surgery may be considered if metatarsus adductus is diagnosed late or if there is a rigid deformity. This is typically pursued after age 4 years.

Internal tibial torsion

Internal tibial torsion (ITT) occurs when the tibia twists inward. This can occur before birth as the legs rotate to fit in the confined space of the womb. After birth, an infant’s legs should gradually rotate to align properly. If the lower leg remains turned in, the result is ITT. When the child begins walking, the feet turn inward because the tibia in the lower leg points the foot inward.

Internal tibial torsion typically is bilateral and presents in toddlers aged 1 to 4 years.³ Parents may describe the child as frequently tripping, being clumsy, or stepping on his/her own feet while walking. Torsional issues such as ITT become more obvious with fatigue or fussiness.

Rotational issues can be seen during gait observation. Children with ITT will have knees directed straight ahead while walking, but inward rotation of the lower leg(s) causing intoed gait. Physical examination shows a thigh-foot angle of at least -10° and an inward foot progression angle.¹⁰ No imaging is needed.

As the tibia grows longer, it usually untwists on its own. Tibial torsion almost always improves without treatment, and usually before school age. Ninety-five percent of children will spontaneously resolve, usually by preschool or kindergarten.¹¹ Splints, special shoes, and exercise programs have not been shown to speed the process. Surgery to reset the bone (tibial rotational osteotomy) may be done in a child who is aged at least 8 to 10 years and has a severe twist that causes significant functional issues. This is rare.

Femoral anteversion

Femoral anteversion occurs when the femur is medially rotated on its long axis from birth. The shape of the proximal femur allows the hip joint to have significantly more internal rotation than external. As a result, both the knees and the feet point inward. It is often most obvious in children aged about 5 or 6 years.

Rotational profile shows the hips to have at least 60° of internal rotation. Families may describe the child as having “poor turnout” in ballet class or may say the child doesn’t like to sit “crisscross applesauce” in school. Children often sit in the W position, with their knees bent and their feet flared out behind them.

They also may complain of their knees bumping into each other while walking-a finding casually referred to as “kissing knees.”¹²

Femoral anteversion is also nearly always a benign condition that improves gradually in most children (>80%) by age 10 years, although it may not ever resolve completely.¹³ Mild to moderate femoral anteversion should also be considered a variant of normal anatomy, rather than a pathologic entity. There are no braces or exercises that will improve or correct this problem. Imaging typically is not needed. Furthermore, there is no evidence that sitting position, such as W-sitting, impacts this condition, and thus children should be allowed to sit in whatever position they find comfortable. If the femoral anteversion is severe and persists, the only definitive treatment would be rotational osteotomy of the femurs after age 10 years. This surgery is performed very rarely-less than 1% of children with this condition.¹⁴

NEXT: Knock knee, flatfoot, and pronation

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

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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

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.

Next: Detecting developmental dysplasia of the hip

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.

Summary

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.

REFERENCES

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