Orthotic Treatment of Flat Feet in Children
with Low Muscle Tone
By Carolyn Kates, MS, PT
What causes flat feet in children with hypotonia?
Low muscle tone, also known as hypotonia, contributes to joint hypermobility (Parker
and Bronks, 1980). Hypermobility, also called ligamentous laxity, allows the foot to roll
inward, giving the appearance of no foot arch. One of the bones in the middle of the
foot arch, the navicular bone, may protrude down and out. This flat foot appearance is
also often termed midfoot pronation. If the flat foot becomes too severe, the child may
start to walk on the inside of the foot rather than the bottom of the foot (Bleck, 1982).
Children with hypotonia also may walk with their feet spread more widely apart and their
hips turned outward (i.e., external rotation) more than other children (Caselli, CohenSobel, Thompson, Adler, and Gonzalez, 1991). This posture is often associated with
decreased balance reactions, a common feature of children with hypotonia (Grossman,
1990). Caselli and his colleagues noted how this wide-based gait with external hip
rotation contributes to further walking instability in the forward direction. Another
common pattern in children with hypotonia is external rotation of the feet. This outward
foot rotation, also known as a toeing-out pattern, further contributes to the flat foot
position (Cusick and Stuberg, 1992).
What are some of the reasons for using foot orthoses for children with
hypotonia?
According to the medical literature, there are three primary reasons for using foot
orthoses with a child with flat feet and hypotonia: (1) prevent future foot deformity; (2)
prevent future pain; and (3) improve stability and energy expenditure during walking.
The young child’s foot has more cartilage and is more flexible than an adult’s foot
(Bleck, 1982). Spencer and Person (1984) noted that a young child whose feet are not
in alignment is usually without pain. According to Bleck (1982) cartilage degeneration
may occur when the joint surfaces are not in proper contact with each other. If one joint
is out of alignment, then other joints above and below the original joint may also lose
alignment (Donatelli, 1996). Over time, as the child ages, the foot’s structure of not
being in alignment tends to become more rigid and arthritic changes and pain may set
in (Bleck, 1982; Caselli, et al., 1991; Miller, Laslowski, and Suman, 1996; Mosca, 1996;
Staheli, 1999). Foot orthoses can provide the external support needed to keep the
child’s foot in better alignment, and therefore prevent future foot deformity and pain.
Another important reason orthoses may be beneficial for young children with flat feet
and hypotonia is to improve efficiency of walking. Researchers who have studied
children with hypotonia noticed these children tend to take shorter steps, walk slower,
and use the toeing-out pattern and a wide base of support compared to children with
normal tone (Parker, Bronks, and Snyder, 1985). The muscles responsible for walking
directly forward are not fully utilized with the toeing-out pattern and do not efficiently
propel the body forward (Calliet, 1983; Donatelli, 1996; Sutherland, 1989; Valmassy,
1994). Shamp (1989) recommended controlling the flat foot gait pattern through the use
of ankle-foot orthotics.
What are some of the precautions and contraindications when using foot
orthothes in young children with hypotonia?
A variety of medical authors urged caution in being too hasty to prescribe orthotic
treatment for children with flat feet. According to medical literature, most young children
with flat feet will naturally improve over time (Barry and Scranton, 1983; Bleck, 1982;
Spencer and Person, 1984; Trott, 1982). Bleck reported that only 5-15 percent of leg
abnormalities persist beyond skeletal maturity, which generally occurs during the
teenage years. Bleck reminds us that joint cartilage needs movement to survive and
repair itself; and that joints that are stabilized for too long become rigid. It is important
to note, however, that these medical authors studied children who were typically
developing. The muscle tone of the children was within the normal range, unlike the
population of children with hypotonia.
Is there research evidence that foot orthoses improves the walking function of
children with hypotonia?
Martin (2004) studied fourteen children with Down syndrome and hypotonia between
the ages of 3-½ years to 8 years. This researcher compared a group of children
wearing orthoses above the ankle, supramalleolar orthoses, with a group of children not
wearing orthoses, over a period of 10 weeks. Standardized motor tests were used to
measure the children’s progress. Joint laxity was taken into consideration as a potential
influence on the treatment response. Significant improvement was observed in the
group of children wearing the orthoses that could not be attributed solely to maturation
and growth. The amount of joint laxity in each individual child did not affect the
outcome.
Selby-Silverstein, Hillstrom, and Palisano (2001) used advanced technological
measurements in a gait analysis laboratory to study 16 children with Down syndrome
and a control group of 10 children without disabilities. All 26 children in this study
ranged in age from 3-6 years. The orthoses in this study were cut below the ankle
(submalleolar orthoses). The children with Down syndrome had more neutral foot
alignment, showed decreased toeing-out during walking, and were more consistent in
their walking patterns while wearing the orthoses compared to not wearing them.
Speed of walking did not change between the two conditions.
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Kates (2000) performed a single subject design study on a 4-year old child with Down
syndrome and hypotonia comparing two types of supramalleolar orthoses and a control
baseline of not wearing orthoses. One type of orthoses had a design at the toe to
control toeing-out, called a gait-plate design, and a rigid, carbon fiber laminate on the
bottom. The other type of orthoses had a regular toe design. The gait-plate design of
orthoses with the rigid bottom was associated with an increased step length and speed
of walking compared to either the orthoses with the regular toe design without the rigid
bottom or the baseline of not wearing orthoses.
Grossman (1990) studied four subjects between the ages of 2.5-5.5 years comparing
hand fabricated, soft plastic, submalleolar orthoses, (Pelite and moleskin) to the
condition of not wearing orthoses. A study of footprints, called pedographs,
demonstrated improvement in three of the four subjects in the areas of decreased
toeing-out and increased step length. Younger children with mild flat feet demonstrated
greater change then older child with moderate flat feet.
What further research needs to be done to evaluate the effect of foot orthoses for
children with hypotonia?
Of the very few studies that have been published on children with low muscle tone and
orthoses, the positive changes noticed have been in foot alignment and walking
patterns. The changes that were documented occurred over a relatively short period of
time. Further research questions that need to be studied include:
(a) Is there a difference in outcomes between supramalleolar (above the ankle)
orthoses compared to submalleolar (below the ankle) orthoses?
(b) Is there a difference in outcomes with different severities of bony alignment in
individual children: mild, moderate, or severe?
(c) What are the benefits and consequences of individuals with hypotonia and flat
feet wearing the orthoses for a long term? Does the correction of the foot alignment last
after the orthoses are removed, or does the individual need to continue wearing the
orthoses throughout life? Does wearing the orthoses over a long period of time prevent
the feet from becoming naturally stronger? If the individual’s feet do not strengthen
from wearing the orthoses, do the benefits of improved foot alignment and efficiency of
walking outweigh the possibility of wearing the orthoses over a long period of time?
Further exploration of these questions may offer suggestions for future research
studies.
References
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