R E S E A R C H
A R T I C L E
A Pilot Study to Profile the Lower
Limb Musculoskeletal Health in
Children With Obesity
Grace O’Malley, MSc, BSc; Juliette Hussey, MSc, PhD; Edna Roche, MD, FRCPI
Physiotherapy Department, Children’s University Hospital (Ms O’Malley), Dublin, Ireland; Discipline of Physiotherapy,
School of Medicine, University of Dublin Trinity College (Dr Hussey), and Department of Paediatric Endocrinology,
Adelaide, Meath and National Children’s Hospital (Dr Roche), Dublin, Ireland.
Purpose: Evidence suggests a negative effect of obesity on musculoskeletal health in children. A pilot study
was undertaken to investigate the presence of musculoskeletal impairments in children with obesity and to
explore the relationships among body mass index, physical activity, and musculoskeletal measures. Methods:
Lower limb musculoskeletal health (pain, power, balance, flexibility, and range of motion), physical activity,
and screen time were assessed using standardized methods. Results: Seventeen children (mean age = 12.21
years) participated. Mean values for lower limb musculoskeletal measures are presented. Moderate negative
correlations were found between body composition and range of motion, flexibility, and strength. Genu
valgum deformity was moderately positively correlated to body mass index. Conclusions: The results of this
pilot study suggest that children who are obese may present with musculoskeletal impairments of the lower
limb. Clinicians working with children who are obese should conduct a thorough musculoskeletal assessment
and consider the presence of impairments when promoting physical activity. (Pediatr Phys Ther 2012;24:292–
298) Key words: adolescence, body mass index, body weight, child, correlational study, muscle strength,
musculoskeletal system, obesity, overweight, pain, physical activity, physical fitness, postural balance, range
of motion
INTRODUCTION
The effect of obesity on the musculoskeletal system
has been described for adults who are overweight, but
limited data exist regarding the musculoskeletal health of
children who are obese.1-6 Musculoskeletal fitness encompasses parameters such as joint range of motion (ROM),
muscle strength, muscle flexibility, balance, and coordi-
0898-5669/110/2403-0292
Pediatric Physical Therapy
C 2012 Wolters Kluwer Health | Lippincott Williams &
Copyright Wilkins and Section on Pediatrics of the American Physical Therapy
Association
Correspondence: Grace O’Malley, MSc, BSc, Physiotherapy Department,
Children’s University Hospital, Temple Street, Dublin 1, Ireland ([email protected]).
Grant Support: This work was supported by postgraduate funding granted
to GO’M via the Hussey-Gormley Studentship at the University of Dublin,
Trinity College.
This work was completed as part of an MSc in research for Ms O’Malley.
The authors declare no conflict of interest.
DOI: 10.1097/PEP.0b013e31825c14f8
292
O’Malley et al
nation. Impairments of the musculoskeletal system can
lead to pain and discomfort and subsequent activity restriction. All of these parameters are of particular interest
to physical therapists whose practice and therapeutic interventions aim to reduce physical limitations of clients
who are overweight. Identifying physical impairments and
removing barriers to activity assist a client who is overweight in participating in the lifestyle changes necessary
for overall good health.
ROM parameters are commonly used as indicators
and predictors of physical function.7 Joint ROM is influenced by bony structure and the extensibility of soft tissue
structures. Restrictions of lower limb soft tissue are physical impairments commonly associated with musculoskeletal conditions.7-10 In addition, impaired muscle flexibility may predict the presence of future musculoskeletal
symptoms.11 Previous investigators have observed that
children who are obese present with less flexible hamstrings than children of healthy weight12 ; reduced hip joint
ROM, reduced hamstring flexibility, and increased body
mass index (BMI) have each been identified as predictors of low back pain.8,13-15 In addition, restricted ROM
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has been reported to adversely affect standing balance,2
postural adjustment,12 and movement efficiency.16 Furthermore, appropriate muscle strength is essential to ease
the loading of joints, and it is thought that in individuals
who are overweight, the dampening capability of muscles
is impaired because of muscle weakness and the resistance offered by body weight, thus increasing the rate of
joint loading.17 Finally, gait studies of children propose
that obesity leads to increased postural sway, and that gait
and postural adaptations contribute to the development of
lower limb varus/valgus deformities.18,19
Purpose
Against the backdrop of previous investigations, the
current pilot study was designed to profile the lower limb
musculoskeletal health of children who are obese to guide
practice and appropriate therapeutic intervention. In addition, the study was designed to identify any relationships
that existed between musculoskeletal measures, BMI, and
physical activity (PA) level.
METHODS
Subjects
Consecutive patients attending the Outpatient Pediatric Endocrinology Clinic in Adelaide, Meath and National Children’s Hospital in Dublin, Ireland, were recruited for this study between January and August of 2006.
Children were included in the study if they presented with
exogenous obesity, a BMI greater than the 97th percentile
for age, and were between 10 and 15 years of age. Subjects
were excluded from the study if they had sustained any
musculoskeletal injury in the previous 6 months or were
unable to take part in the study procedures. Ethical permission was obtained from the Research Ethics Committee of Saint James Hospital/Adelaide, Meath and National
Children’s Hospital. The study procedure was explained
to parents and children, and written informed consent was
obtained from parents, who were present with their children at all times during data collection.
Procedures
Musculoskeletal History. A subjective history was
taken from children and parents relating to past musculoskeletal events involving the lower limb that required
medical treatment. Medical records were reviewed to confirm these events. Eligible participants completed a pain
profile and a visual analogue scale relating to reported
lower limb complaints.
Demographics and Anthropometry
Patient details such as gender, age, height, and weight
were collected. Height (to nearest 0.1 cm) was measured in
triplicate using a wall-mounted stadiometer (Holtain Ltd,
Pediatric Physical Therapy
Crymmych, PENBS, UK). Weight (to the nearest 0.1 kg)
was measured in triplicate using an electronic scale (Seca
Ltd., Birmingham, UK). Waist circumference was measured (to nearest 0.1 cm) using a measuring tape placed
midway between the distal margin of the rib cage and
the proximal margin of the iliac crest. BMI was calculated
(BMI = weight (kg)/height (m)2 ), and the BMI standardized deviation score was calculated as recommended by
Cole.20 Children were classified as moderately obese (BMI
= 25-29.99 kg/m2 ) or severely obese (BMI > 30 kg/m2 ).
Physical Activity and Sedentary Levels. Physical activity levels were measured using the Modifiable Activity Questionnaire for Adolescents (MAQA), which yields
a reasonable estimate of habitual PA in adolescents and
can be used to calculate metabolic equivalents (METs) per
hour per week.21 Sedentary time was assessed by measuring screen time, the number of hours spent using a screen
per day (eg, watching television, playing video games, and
using a cell phone for entertainment).
Joint ROM and Muscle Flexibility. Measures of passive
joint ROM of the hip, knee, and ankle were taken using
standardized techniques and using a universal goniometer (MedFaxx Incorporated, Wake Forest, North Carolina)
and an angle finder for hip rotation (Dasco Pro, Inc, Rockford, Illinois).22 Muscle flexibility was measured by assessing the muscle length of quadriceps, hamstrings, and
the gastrocnemius, using the quadriceps angle test, the
popliteal angle test, and the gastrocnemius length test.
Intramalleolar gap distance was measured in centimeters
using calipers (MedFaxx Incorporated) and served as a
surrogate measure of genu valgum.
Balance Testing. Standing balance was assessed using
timed unipedal static and dynamic measures as recommended by Emery et al.23 Subjects were asked to stand on
1 leg with the opposite knee held at 90◦ of flexion and with
the upper limbs relaxed. Subjects performed a timed (to
the nearest 0.1 second) static single-leg stance on a hard
floor, with their eyes open followed by eyes closed. A timed
dynamic single-leg test was performed standing on foam of
uniform density measuring 16.4 × 20 × 2.5 with eyes
open and closed. Each test was performed 3 times.
Isokinetic Muscle Strength. The lower limb concentric muscle strength of knee flexors and extensors was
measured using isokinetic dynamometry (Biodex System
3, Biodex Corp., Shirley, New York), which yields valid
and reliable results. Specialized pediatric attachments and
additional seat padding that allowed the lower leg to hang
freely from the edge of the seat were used. Test velocities
of 60◦ per second, 90◦ per second, and 180◦ per second
were employed.
Data Analysis
Anthropometric measures (height and weight) were
collected in triplicate, BMI, and the mean value for each
of these measures was calculated. The mean results for
ROM and balance testing were calculated and raw isokinetic data were normalized to body weight. Thereafter,
Musculoskeletal Health in Children With Obesity
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the mean torque/body weight scores for both lower limbs
were computed. All data from measured variables were entered into SPSS for Mac OS X version 11.0.2. Descriptive
statistics were used to elucidate the mean and standard
deviation for all measures. Kolmogorov-Smirnov Z tests
were performed to assess whether data approximated a normal distribution. In addition, correlational tests (bivariate
Pearson correlation coefficients) were used to investigate
the relationships between variables, and differences between groups were investigated using nonparametric tests
(Mann-Whitney U test and Wilcoxon W). An α level of
0.05 was used as the criterion of statistical significance.
Joint ROM and Muscle Flexibility
Table 2 presents the results for joint ROM. The mean
popliteal angle for the cohort was 43.59◦ ± 6.61◦ , and
for boys and girls, respectively, were 42.93◦ ± 8.66◦ and
44.1◦ ± 5◦ . The mean measure of quadriceps length for
the cohort was 116.91◦ ± 12.23◦ , and for boys and girls,
respectively, were 121.93◦ ± 12.93◦ and 113.4◦ ± 11◦ . The
mean length of gastrocnemius for the cohort was 91.41◦ ±
5.06◦ , and for boys and girls, respectively, were 92.78◦ ±
2.64◦ and 90.45◦ ± 6.20◦ .
Standing Balance
RESULTS
Study Cohort
Table 1 describes the participant characteristics. Six
children (boys: n = 4; girls: n = 2) were classified as
moderately obese and 11 children (boys: n = 3; girls:
n = 8) were classified as severely obese. The mean age
of children was 12.41 years and the mean BMI was 32.45
kg/m2 (95% confidence interval [CI]: 29.35-36.09 kg/m2 ).
The mean bilateral balance measures for the group
were 30.84 ± 33.35 seconds and 13.47 ± 9.66 seconds for
static standing balance with the eyes open and closed, respectively. For dynamic balance, the mean values obtained
were 22.05 ± 21.06 seconds and 3.09 ± 1.20 seconds with
the eyes open and closed, respectively.
Isokinetic Muscle Strength
Mean torque/body weight values measured for knee
flexion and extension are described in Table 3.
Previous Orthopedic History and Current Pain
Fifty-three percent of the group (n = 9; 2 boys) had
sustained a previous fracture or soft tissue injury of the
lower limb that required a hospital attendance in the past
(between 6 and 18 months prior to the study) and 72%
(6 boys) reported having pain in their lower limbs.
Physical Activity Levels and Sedentary Levels
Children were spending 20.46 ± 16.8 hours per week
(boys 17.4 ± 6.6; girls 22 ± 20 hours per week) in habitual PA as measured using the MAQA. Children reported
engaging in screen time for 3 ± 1 hours every weekday
and for 3.5 ± 2 hours on weekend days.
The Relationship Between BMI and
Musculoskeletal Measures
When measures of BMI were correlated to musculoskeletal indices (Table 4), moderate relationships with
statistical significance significant were found for hip flexion ROM (r = −0.65, P < .001), hip abduction ROM
(r = −0.65, P < .001), knee flexion ROM (r = −0.69,
P < .001), knee flexion strength (r = −0.55, right leg;
r = −0.58, left leg, P < .05), and flexibility of quadriceps (r = −0.51, P < .05) and gastrocnemius (r =
−0.57, P < .001). Positive correlations were observed between BMI measures and measures of knee hyperextension
TABLE 1
Anthropometric Characteristics of Participants, Mean (95% Confidence Interval)
Age (y)
Height (cm)
Weight (kg)
BMI (kg/m2 )
BMI SDS
BMI P
WC (cm)
Male
n=7
Female
n = 10
Total
n = 17
10.95
(9.34, 12.56)
148.2
(137.14, 160.2)
64.28
(51.59, 76.96)
28.82
(25.82, 31.82)
2.25
(2.09, 2.41)
98.76
(98.21, 99.19)
95.32
(84.40, 103.23)
13.44
(12.07, 14.82)
164.30
(158.40, 170.20)
96.07
(80.46, 111.67)
35.45
(30.43, 40.47)
2.31
(2.12, 2.51)
98.84
(98.19, 99.08)
116.17
(104.52, 127.83)
12.41
(11.29, 13.55)
157.33
(151.38, 164.36)
82.98
(70.40, 95.55)
32.45
(29.35, 36.09)
2.28
(2.17, 2.41)
98.81
(98.38, 99.08)
106.55
(97.15, 115.94)
Abbreviations: BMI = body mass index; BMI SDS = BMI standardized deviation score;
BMI P = BMI percentile; WC = waist circumference.
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O’Malley et al
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TABLE 2
Passive Joint Range of Motion for the Lower Limb, Mean (95% Confidence Interval)
Hip flexion
Hip abduction
Hip extension
Hip internal rotation
Hip external rotation
Knee flexion
Knee extension
Ankle dorsiflexion
Ankle plantarflexion
Male
n=7
Female
n = 10
Total
n = 17
110.36
(102.00, 118.72)
54.79
(49.94, 59.63)
25.64
(20.69, 30.60)
45.57
(36.99, 54.15)
58.5
(46.05, 70.95)
135.29
(131.18, 139.39)
3.21
(1.41, 5.02)
92.78
(90.34, 95.23)
41.28
(34.71, 47.86)
103.45
(91.15, 115.75)
42.5
(36.76, 48.24)
23
(20.03, 25.97)
44.65
(37.26, 52.04)
68.1
(63.43, 72.77)
128.45
(122.31, 134.59)
2.1
(0.50, 4.64)
90.45
(86.01, 94.89)
43.95
(36.94, 50.96)
106.29
(98.85, 113.73)
47.55
(42.81, 52.31)
24.08
(21.66, 26.51)
45.02
(40.08, 49.98)
64.15
(58.62, 69.68)
131.26
(127.25, 135.28)
2.56
(1.03, 4.09)
91.41
(88.81, 94.02)
42.85
(35.40, 47.30)
(r = 0.55, P < .001) and genu valgum (intramalleolar gap
[r = 0.67, P < .001]). Nonparametric independent samples tests (Mann-Whitney U tests) revealed that children
who were severely obese had less knee flexion (P = .015)
than those who were less obese.
The Relationship Between PA and Musculoskeletal
Measures
A positive relationship was observed between PA and
muscle strength (peak torque/body weight) for knee flexion/body weight at 60◦ per second (r = 0.76, P < .001),
90◦ per second and 180 per second (r = 0.62, r = 0.55,
respectively, P < .05). Further positive correlations were
observed between PA and static balance (r = 0.64, right
leg; P < .05, left leg) for eyes closed and (r = 0.70,
P < .001) for eyes open.
Significant correlations were observed between sedentary activity measured by screen hours per weekday and
peak torque/body weight for knee flexion (r = −0.59 at
60◦ per second.; r = −0.60 at 90◦ per second and r =
−0.49 at 180◦ per second, P < .05) and extension at 60◦
per second. (r = −0.50, P < .05) and 180◦ per second
(r = −0.62, P < .001). Children who reported spending
more than 2 hours engaging in screen time per day had
significantly lower knee extension strength at 90◦ per second (P = .007) and 180◦ per second (P = .003) than those
children who engaged in less than 2 hours of screen time
per day.
DISCUSSION
The current pilot study was designed to profile the
lower limb musculoskeletal health of children who are
obese in order to guide practice and appropriate therapeutic intervention. In addition, the study was designed
Pediatric Physical Therapy
to identify any relationships that existed between musculoskeletal measures, BMI, and PA level.
It was observed that half of the group had previous
lower limb injury, with more than 40% having sustained
a fracture of the lower limb. Currently, in Ireland, no national data are available pertaining to the incidence of musculoskeletal injury in children and therefore comparison
to normative data is not possible. As the study did not
include a control group, previous reports of greater musculoskeletal injury in children who are obese cannot be
supported. In this study, lower limb pain was reported
by 72% of the group. Without the inclusion of a control
group, it is unknown whether children who are obese report more musculoskeletal pain than their peers who are
leaner; however, the work by Bell et al24 observed a greater
likelihood of musculoskeletal pain in children who are
overweight and obese compared with lean controls. Children who were obese were 4.09 times more likely to report
pain than controls (odds ratio, P < .05). Similarly, Krul
et al25 observed more self-report musculoskeletal problems in adolescents (12-17 years) who were obese when
compared with counterparts who were lean (odds ratio =
1.69; P < .05). As pain may act as a barrier to the lifestyle
changes necessary to facilitate effective obesity management, it is vital that musculoskeletal discomfort is screened
during the assessment of children with obesity. Previous
work has identified knee pain as the most common symptom reported by children who are overweight.2,24 In the
current study, foot pain (53%) was the most commonly reported symptom followed by knee pain (12%). The effect
of childhood obesity on foot function warrants attention as
flattening of the medial longitudinal arch may place greater
strain on soft tissue structures of the medial lower limb and
thus increase the potential for musculoskeletal injury. Krul
et al observed greater self-reported ankle and foot problems
(odds ratio = 1.89; 95% CI: 0.85, 4.17) compared with hip
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TABLE 3
Mean (%) Isokinetic Torque/Body Weight for the Knee Joint
Mean (95% CI)
Gender
Boys
Girls
Total
Flexion, 60◦ /s
Flexion, 90◦ /s
Flexion, 180◦ /s
Extension, 60◦ /s
Extension, 90◦ /s
Extension, 180◦ /s
63.79 (55.60, 72.19) 58.24 (48.92, 70.17) 53.20 (40.89, 65.50) 117.94 (101.24, 138.56) 117.76 (93.39, 142.13) 95.17 (72.14, 118.24)
59.35 (49.96, 68.73) 53.88 (44.01, 63.75) 41.94 (33.26, 50.60) 142.15 (120.81, 163.48) 120.32 (101.03, 139.61) 88.01 (72.97, 103.05)
61.18 (54.99, 67.11) 55.68 (49.35, 62.67) 46.01 (39.30, 53.01) 132.18 (133.80, 119.08) 117.53 (106.12, 132.60) 89.79 (79.52, 101.86)
Abbreviation: CI, confidence interval.
TABLE 4
Correlations Between Musculoskeletal Measures, Body Mass Index (BMI), and Physical Activity
Hip flexion
Hip abduction
Hip IR
Knee flexion
Knee extension
Ankle DF
Popliteal angle
Quadriceps angle
F, 60◦ /s
F, 90◦ /s
F, 180◦ /s
E, 60◦ /s
E, 90◦ /s
E, 180◦ /s
IM gap
BMI, kg/m2
BMI SDS
BMI P
− 0.652a
− 0.609a
− 0.539b
− 0.646a
− 0.168
− 0.695a
0.551b
− 0.570a
− 0.172
− 0.510b
− 0.567b
− 0.584b
− 0.546b
0.031
− 0.164
− 0.096
0.670a
− 0.441
− 0.324
− 0.525b
0.733a
− 0.348
− 0.377
− 0.311
− 0.328
− 0.245
− 0.310
− 0.129
− 0.045
0.258
0.585b
− 0.280
− 0.348
− 0.441
0.633a
− 0.150
− 0.318
− 0.244
− 0.420
− 0.352
− 0.162
− 0.164
− 0.144
0.180
0.476
Waist
Circumference
(cm)
MET, h/ wk
Screen, h/d
− 0.445
− 0.492
0.129
− 0.660b
0.334
− 0.593b
0.191
− 0.701a
− 0.425
− 0.494
− 0.653b
0.119
− 0.261
− 0.328
0.562b
− 0.099
0.123
− 0.429
0.135
− 0.631b
0.477
0.127
− 0.209
0.264
0.290
0.318
0.528
0.671a
0.499
− 0.096
0.230
− 0.096
0.733a
0.076
0.203
− 0.277
− 0.194
− 0.219
− 0.628a
− 0.597b
− 0.493
− 0.465
− 0.637a
− 0.599b
− 0.223
Abbreviations: BMI P, body mass index percentile; BMI SDS, body mass index standardized deviation score; DF, dorsiflexion; E, mean torque/body
weight for extension; F, mean torque/body weight for flexion; IM, Intramalleolar; IR, internal rotation; MET, metabolic equivalent.
Significant correlations are noted in bold.
a Correlation is significant at 0.01 level (2-tailed) using Pearson product moment correlations.
b Correlation is significant at 0.05 level (2-tailed).
and knee problems (odds ratio = 1.70; 95% CI: 0.80, 3.58)
in children who were overweight and obese compared with
controls who were lean.25 Although Krul and colleagues
did not objectively assess participants, the results indicate
an increased prevalence of lower limb discomfort in children who are obese. In addition, the authors reported that
children aged 12 to 17 years who were overweight and
obese consulted a family physician with lower limb complaints more frequently than peers who were lean (odds
ratio = 1.92, 95% CI: 1.05, 3.51; P < .05). Significant associations have been observed between obesity and low back
pain, lower limb pain, genu valgum, knee hyperextension,
and tight quadriceps.26 Obesity may have a negative effect
on the osteoarticular health of children through the promotion of biomechanical changes in the lumbar spine and
lower limbs, and for this reason musculoskeletal examination in the assessment of children who are overweight is
recommended. The results of this pilot study confirm that
musculoskeletal discomfort should be screened in children
who are obese.
Activity was measured and results indicated that children were spending more than 20 hours per week in
habitual PA. Therefore, it would appear that the study
cohort was reaching recommended guidelines of 60 min-
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O’Malley et al
utes per day of moderate activity. These results should
be interpreted with caution, as the MAQA is a self-report
questionnaire and may not accurately reflect the actual
amount or intensity of activity performed. Children in the
study reported engaging in screen time more than the recommended cutoff level of 2 hours per day.
Another objective of this study was to profile the objective lower limb musculoskeletal fitness of the cohort.
Normative data for joint ROM and flexibility measures
in children are limited. Therefore, whether joint ROM was
reduced in this cohort is unclear. Work by Bell et al24 compared lower limb ROM in children who were overweight
and obese with counterparts who were lean and reported
no observed differences.24 The authors did not describe
the methods used to assess ROM and as such these results
should be considered with caution. Our results suggested
that children who are obese have less gastrocnemius flexibility than reported normative values,26 and as reduced
gastrocnemius flexibility can affect ankle dorsiflexion and
balance, this finding should be investigated in future controlled trials. Goulding et al18 suggest that boys who are
overweight have significantly impaired balance compared
with controls of healthy weight. Future research is recommended to investigate the influence of obesity on balance.
Pediatric Physical Therapy
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Impaired muscle strength and subsequent functional
limitation in children who are obese has been reported.28
We have presented data regarding the isokinetic strength
of children who are obese, but these data should be interpreted with caution because of the lack of information
regarding the pubertal status of our sample. Because of
the influence of lower limb muscle strength on developing peak bone mass and bone strength, it is recommended
that future studies investigate whether children who are
obese have reduced muscle strength compared with children matched for pubertal status, gender, age, and height.
The final objective of this study was to examine the
relationships between BMI, PA, and musculoskeletal measures. Inverse associations were observed between BMI and
lower limb ROM. These findings have not been reported
elsewhere. A reasonable assumption, however, is that in an
individual who is obese, joint excursion would likely be
limited by excess deposits of subcutaneous adipose tissue.
The finding that children who were severely obese had less
knee flexion ROM than those who were moderately obese
supports this hypothesis. Similarly, such limitation of ROM
might affect the flexibility of lower limb musculature. Using the femur as a lever, the hamstrings influence pelvic
tilt, which is particularly important in the growing child,
where muscle tightness can affect posture, gait, and low
back discomfort.12 In this study, significant negative relationships were observed between body composition and
lower limb flexibility, supporting previous findings.12,26
Whether flexibility is impaired in children who are obese
compared with children who are of healthy-weight requires
further investigation, and such study should also assess the
functional implication of these impairments.
Our results suggested that children who are obese
might present with lower limb misalignment. The significant positive relationship between body composition
and knee hyperextension concurs with previous work,26
in which a greater incidence of knee hyperextension in
children who were obese compared with those of healthy
weight was observed. Considering that knee hyperextension may influence proprioception and the peak joint moments associated with joint loading,29,30 future research
should examine whether children who are obese and
present with knee hyperextension may be at greater risk of
injury compared with controls. The positive relationship
observed between BMI and genu valgum has also been described by Shim et al,31 who reported greater intramalleolar distance in a cohort of children with Prader-Willi syndrome who were obese compared with those who were
not obese. We do not currently understand whether being
overweight during childhood negatively affects developing
joints. Considering the associations between bony anomalies (Blount’s disease and slipped upper femoral epiphysis)
and childhood obesity,27 further study is warranted to investigate the effect of obesity on joint loading, ligamentous
stability, and bony development.
We observed a negative association between BMI and
knee flexion strength. Given the evidence to date regarding
the gait abnormalities observed in children who are obese,
Pediatric Physical Therapy
future investigation should study the relationship between
body composition and the effect of strength indices on
functional capacity. Our results suggested that children
who were more physically active had greater strength and
that a positive relationship existed between PA levels and
standing balance. It cannot be determined from the literature what level of PA is necessary for optimal balance
development in children, but it is reasonable to assume that
for neuromuscular capabilities to develop fully, threshold
levels of physical challenge and external pertubation are
required. Children reporting more screen time had lower
levels of standing balance and greater strength than their
contemporaries who were less sedentary. To date, no studies have reported a negative association between screen
time and muscle strength of children, and therefore this
finding should be investigated further. Our results indicate
that there may be a positive relationship between BMI and
musculoskeletal impairment in children who are obese. In
addition, results suggest an inverse relationship between
PA level and musculoskeletal impairment.
Although this pilot study adds to the current evidence
regarding the effect of obesity on children’s musculoskeletal health, it was greatly limited by a small heterogeneous
sample. Participants taking part in the study were not classified according to Tanner stage of maturity, and in addition, the girls in the sample were older than the boys.
Therefore, the results should be interpreted with caution
as pubertal status may have influenced measures (particularly in the case of muscle strength). Further investigation is warranted using a randomized controlled design
to ensure that no inherent differences between the groups
are confounding the study. Given the limitations of the
study, it is nevertheless recommended that children who
are obese undergo a full musculoskeletal assessment as part
of their general medical assessment and that physical therapy is considered as part of standard care. The presence
of such musculoskeletal impairments as those described
in this small study may adversely affect the time spent in
PA by children who are obese. As increasing PA is a cornerstone of obesity treatment, examining the effect of such
musculoskeletal impairments on PA level is warranted. It is
recommended that physical therapists assess, monitor, and
treat musculoskeletal impairments associated with childhood obesity where appropriate.
CONCLUSION
This small pilot study investigated the presence of
musculoskeletal impairments in obese children and explored the relationships between body composition, PA,
and musculoskeletal measures. The results suggest that
children who are obese may present with musculoskeletal impairments of the lower limb. It is warranted that
children who are obese have a thorough musculoskeletal
assessment to identify such impairments and so that clinicians can prescribe suitable therapeutic exercise to reduce
these impairments.
Musculoskeletal Health in Children With Obesity
297
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REFERENCES
1. Podeszwa DA, Stanko KJ, Mooney JF III, Cramer KE, Mendelow MJ.
An analysis of the functional health of obese children and adolescents
utilizing the PODC instrument. J Pediatr Orthop. 2006;26(1):140143.
2. Taylor ED, Theim KR, Mirch MC, et al. Orthopedic complications of overweight in children and adolescents. Pediatrics.
2006;117(6):2167-2174.
3. Wearing SC, Hennig EM, Byrne NM, Steele JR, Hills AP. The impact of
childhood obesity on musculoskeletal form. Obes Rev. 2006;7(2):209218.
4. Wills M. Orthopedic complications of childhood obesity. Pediatr Phys
Ther. 2004;16(4):230-235.
5. Peltonen M, Lindroos AK, Torgerson JS. Musculoskeletal pain in
the obese: a comparison with a general population and long-term
changes after conventional and surgical obesity treatment. Pain.
2003;104(3):549-557.
6. Lean ME, Han TS, Seidell JC. Impairment of health and quality of life in people with large waist circumference. Lancet.
1998;351(9106):853-856.
7. Hertling D, Kessler RM. Management of Common Musculoskeletal Disorders: Physical Therapy Principles and Methods. 3rd ed. Philadelphia,
PA: Lippincott; 1996.
8. Salminen JJ, Maki P, Oksanen A, Pentti J. Spinal mobility and trunk
muscle strength in 15-year-old schoolchildren with and without lowback pain. Spine (Phila Pa 1976). 1992;17(4):405-411.
9. Smith AD, Stroud L, McQueen C. Flexibility and anterior knee pain
in adolescent elite figure skaters. J Pediatr Orthop. 1991;11(1):77-82.
10. Hills AP, Hennig EM, McDonald M, Bar-Or O. Plantar pressure differences between obese and non-obese adults: a biomechanical analysis.
Int J Obes Relat Metab Disord. 2001;25(11):1674-1679.
11. Mikkelsson LO, Nupponen H, Kaprio J, Kautiainen H, Mikkelsson M,
Kujala UM. Adolescent flexibility, endurance strength, and physical
activity as predictors of adult tension neck, low back pain, and knee
injury: a 25 year follow up study. Br J Sports Med. 2006;40(2):107113.
12. Jozwiak M, Pietrzak S, Tobjasz F. The epidemiology and clinical manifestations of hamstring muscle and plantar foot flexor shortening.
Dev Med Child Neurol. 1997;39(7):481-483.
13. Jones MA, Stratton G, Reilly T, Unnithan VB. Biological risk indicators for recurrent non-specific low back pain in adolescents. Br J
Sports Med. 2005;39(3):137-140.
14. Sjolie AN. Low-back pain in adolescents is associated with poor
hip mobility and high body mass index. Scand J Med Sci Sports.
2004;14(3):168-175.
15. Feldman DE, Rossignol M, Shrier I, Abenhaim L. Smoking. A risk
factor for development of low back pain in adolescents. Spine (Phila
Pa 1976). 1999;24(23):2492-2496.
298
O’Malley et al
16. Mecagni C, Smith JP, Roberts KE, O’Sullivan SB. Balance and ankle
range of motion in community-dwelling women aged 64 to 87 years:
a correlational study. Phys Ther. 2000;80(10):1004-1011.
17. McGraw WS. Posture and support use of Old World monkeys (Cercopithecidae): the influence of foraging strategies, activity patterns,
and the spatial distribution of preferred food items. Am J Primatol.
1998;46(3):229-250.
18. Goulding A, Jones IE, Taylor RW, Piggot JM, Taylor D. Dynamic and
static tests of balance and postural sway in boys: effects of previous
wrist bone fractures and high adiposity. Gait Posture. 2003;17(2):136141.
19. Mikesky AE, Meyer A, Thompson KL. Relationship between quadriceps strength and rate of loading during gait in women. J Orthop Res.
2000;18(2):171-175.
20. Cole TJ, Bellizzi MC, Flegal KM, Dietz WH. Establishing a standard
definition for child overweight and obesity worldwide: international
survey. BMJ. 2000;320(7244):1240-1243.
21. Aaron DJ, Kriska AM, Dearwater SR, Cauley JA, Metz KF, LaPorte
RE. Reproducibility and validity of an epidemiologic questionnaire
to assess past year physical activity in adolescents. Am J Epidemiol.
1995;142(2):191-201.
22. Cusick B. Paediatric Leg’s and Feet: A Review of Musculoskeletal Assessment Procedures (Video). Telluride, CO: Telluride Community
Television Productions; 1995.
23. Emery CA, Cassudat D, Klassen TP, Rosychuk R, Rowe BB. Development of a clinical static and dynamic standing balance measurement
tool appropriate for use in adolescents. Phys Ther. 2005;85:502-513.
24. Bell LM, Curran JA, Byrne S, et al. High incidence of obesity comorbidities in young children: a cross-sectional study. J Paediatr
Child Health. 2011;47(12):911-917.
25. Krul M, van der Wouden JC, Schellevis FG, van Suijlekom-Smit
LW, Koes BW. Musculoskeletal problems in overweight and obese
children. Ann Fam Med. 2009;7(4):352-356.
26. de Sa Pinto AL, de Barros Holanda PM, Radu AS, Villares SM, Lima FR.
Musculoskeletal findings in obese children. J Paediatr Child Health.
2006;42(6):341-344.
27. Thompson GH, Carter JR.Late-onset tibia vara (Blount’s disease).
Current concepts. Clin Orthop Relat Res. June 1990;(255):24-35.
28. Riddiford-Harland DL, Steele JR, Baur LA. Upper and lower limb
functionality: are these compromised in obese children? Int J Pediatr
Obes. 2006;1(1):42-49.
29. Shultz SP, Sitler MR, Tierney RT, Hillstrom HJ, Song J. Effects of
pediatric obesity on joint kinematics and kinetics during 2 walking
cadences. Arch Phys Med Rehabil. 2009;90(12):2146-2154.
30. Loudon JK. Measurement of knee-joint-position sense in women with
genu recurvatum. J Sport Rehabil. 2000;9(1):15-25.
31. Shim JS, Lee SH, Seo SW, Koo KH, Jin DK. The musculoskeletal manifestations of Prader-Willi syndrome. J Pediatr Orthop.
2010;30(4):390-395.
Pediatric Physical Therapy
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