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U N I T 1 2
Musculoskeletal Function
Angular andTorsional Deformities
All infants and toddlers have lax ligaments that become
tighter with age and assumption of the weight-bearing
posture. The hypermobility that accompanies joint
laxity coupled with the torsional, or twisting, forces
exerted on the limbs during growth are responsible for
a number of variants seen in young children. Torsional
forces caused by intrauterine positions or sleeping and
sitting patterns twist the growing bones and can pro-
duce deformities as a child grows and develops.
In infants, the femur normally is rotated to an ante-
verted or forward position with the femoral head and
neck rotated anteriorly with respect to the femoral con-
dyles. Normally this angle is approximately 40 degrees
at birth and declines to 15 to 29 degrees by 8 to 10 years
of age.
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A second source of rotation is found in the tibia.
Infants can have 30 degrees of medial rotation of the
tibia, and by maturity the rotation is between 5 degrees
of medial rotation and 15 degrees of lateral rotation.
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Abnormalities of rotation may include excessive adduc-
tion (turning in or toward the body) or abduction (turn-
ing out or away from the body).
Intoeing and Outtoeing.
The foot progression angle
describes the angle between the axis of the foot and
the line of progression.
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It is determined by watching
the child walking and running, although it is usually
less noticeable when the child is running or barefoot.
Figure 43-13 illustrates the position of the foot in
intoeing and outtoeing. Inward rotation of the foot
is assigned a negative value and outward rotation is
assigned a positive value. The normal value in children
and adolescents is 10 degrees (range −3 to 20 degrees).
Skeletal Disorders in
Children
During childhood, skeletal structures grow in length
and diameter and sustain a large increase in bone mass.
Alterations inmusculoskeletal structure and functionmay
develop as a result of normal growth and developmental
processes or as a result of impairment of skeletal develop-
ment caused by hereditary or congenital influences.
Variations of Normal Growth
and Development
Infants and children undergo changes in muscle tone and
joint motion during growth and development. Intoeing,
outtoeing, bowlegs, and knock-knees occur frequently in
infancy and childhood. They usually cause few problems
and are corrected during normal growth processes. The
normal folded position of the fetus in utero causes phys-
iologic flexion contractures of the hips and a froglike
appearance of the lower extremities (Fig. 43-12). The
hips are externally rotated and the patellae point out-
ward, whereas the feet appear to point forward because
of the internal pulling force of the tibiae. During the 1st
year of life, the lower extremities begin to straighten out
in preparation for walking. Internal and external rota-
tions become equal, and the hips extend.
Musculoskeletal assessment of the newborn is impor-
tant to identify abnormalities that require early inter-
vention, facilitate treatment, establish baselines for
future reference, and educate and counsel parents.
53–56
There are many clinical deviations that are easily cor-
rectable in a newborn. Many others correct spontane-
ously as the child grows.
FIGURE 43-12.
Position of fetus in utero, with tibial bowing
and legs folded. (From Dunne KB, Clarren SK.The origin of
prenatal and postnatal deformities. Pediatr Clin North Am.
1986;33(6):1277–1297; with permission from Elsevier Science.)
A
C
B
Line of
progression
Foot
progression
angle
FIGURE 43-13.
(A)
Intoeing,
(B)
outtoeing,
(C)
intoeing and
outtoeing can be determined by watching a child walk and
comparing the long axis of the foot with the direction in which
the child is walking. If the foot is directed inward, the angle
is negative and indicative of intoeing; if it is positive, it is
indicative of outtoeing.
