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U N I T 1 2
Musculoskeletal Function
knees and toes point in (Fig. 43-16). Children with this
problem are encouraged to sit cross-legged or in the
so-called
tailor position
(with the knees touching and
the legs folded under). If left untreated, the tibiae com-
pensate by becoming externally rotated so that by 8 to
12 years of age, the knees may turn in but the feet no
longer do so. A derotational osteotomy may be done in
severe cases or if there is functional disability.
External femoral torsion is an uncommon disorder
characterized by excessive external rotation of the hip.
Bilateral external torsion is usually a benign condition,
and treatment is observational. When the disorder is
unilateral, slipped capital femoral epiphysis should be
excluded (to be discussed).
54
Tibial Torsion.
Tibial rotation is determined by measur-
ing the thigh–foot angle, which is done with the ankle
and knee positioned at 90 degrees (see Fig. 43-15B).
The angle is formed between the longitudinal axis of
the femur and the longitudinal axis of the foot. Inward
rotation, which is assigned a negative value, indicates
internal tibial torsion, and outward rotation, which is
given a positive value, represents external tibial rota-
tion. Infants normally have a mean angle of −5 degrees
as a consequence of normal in utero position.
54
In mid-
childhood through adult life, the mean angle increases
to about 10 degrees.
Internal
or
medial tibial torsion
(i.e., bowing of the
tibia) is a rotation of the tibia that makes the feet appear
to turn inward. It is the most common cause of intoeing
in children younger than 2 years of age.
55
It is present at
birth and may fail to correct itself if children sleep on
their knees with the feet turned in, or sit on in-turned
feet. It is thought to be caused by genetic factors and
intrauterine compression, such as an unstretched uterus
during a first pregnancy or intrauterine crowding with
twins or multiple fetuses. Tibial torsion improves natu-
rally with growth, but this may take several years.
54
External
or
lateral tibial torsion
is a much less com-
mon disorder. It is usually seen between 4 and 7 years
of age, and is often unilateral.
54
The natural growth
rotates the tibia externally, and hence external tibial
rotation can become worse with time.
54,55
Clinically, the
patella faces outward when the foot is straight. There
may be associated patellofemoral instability with knee
pain. Although some correction may occur with growth,
extremely symptomatic children may require surgical
correction, which is usually done after 10 years of age.
GenuVarum and GenuValgum
Genu varum and genu valgum are common pediat-
ric deformities of the knee. As children grow, lower
limb alignment usually follows a predicable pattern
(Fig. 43-17). Genu varum, or bowlegs, is an outward
bowing of the knees greater than 1 inch when the medial
malleoli of the ankles are touching. Most infants and
toddlers have some bowing of their legs up to 18 months
of age. If there is a large separation between the knees
(>15 degrees) after 2 years of age, the child may require
bracing. Genu varum can cause gait awkwardness and
increased risk for sprains and fractures. The child also
should be evaluated for diseases such as rickets or tibia
vara (i.e., Blount disease, to be discussed).
Genu valgum,
or
knock-knees,
is a deformity in
which there is decreased space between the knees.
58,59
The medial malleoli in the ankles cannot be brought
in contact with each other when the knees are touch-
ing. Valgum normally develops after age 24 months
and is most apparent between 3 and 4 years of age (see
Fig. 43-17). By 7 years of age, the lower limb is in slight
valgum and changes very little thereafter. Genu valgum
can be ignored up to 7 years of age, unless it is more
than 15 degrees, unilateral, or associated with short
stature. It usually resolves spontaneously and rarely
requires treatment. Uncorrected genu valgum may cause
subluxation and recurrent dislocation of the patella,
with a predisposition to chondromalacia and joint pain
and fatigue. If genu varum or genu valgum persists and
is uncorrected, osteoarthritis may develop in adulthood
as a result of abnormal intra-articular stress.
Idiopathic tibia vara,
or
Blount disease,
is an abnor-
mal pathologic, developmental bowing that results
from altered growth of the upper medial epiphysis
58,59
(Fig. 43-18). Although the cause of tibia vara remains
unknown, it may occur secondary to growth suppres-
sion from increased compression forces across the
medial aspect of the knee. Blount disease is more com-
mon in obese children who are early walkers. It is also
more common in black children. It may be unilateral, in
contrast to physiologic bowing, which is almost always
Femoral
head
Femoral
anteversion
Internal
tibial
torsion
Femoral
condyles
Tibia
FIGURE 43-16.
Femoral anteversion and internal tibial
rotation. Femoral anteversion normally decreases from about
40 degrees at birth to 15 degrees at maturity, and internal tibial
rotation from 5 degrees at birth to 15 degrees at maturity.
