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technical note



A New Device for Assessing
Ankle Dorsiflexion Motion:
Reliability and Validity


linical and epidemiological studies have identified limitation
in ankle dorsiflexion and increased ankle stiffness as key
contributors to the evolution of foot and ankle pathology.8,16,26 A
lack of robust measurement techniques to quantify ankle range
of motion (ROM) and stiffness, however, has limited our ability to assess
TTSTUDY DESIGN: Clinical measurement.

TTOBJECTIVE: To determine the validity and reli-

ability of measures obtained using a custom-made
device for assessing ankle dorsiflexion motion and

TTBACKGROUND: Limited dorsiflexion has

been implicated in the evolution of foot pain in
a number of clinical populations. Assessment
of ankle dorsiflexion range of motion (ROM) is,
therefore, commonly performed as part of a foot
and ankle examination. Conventional goniometric
assessment methods have demonstrated limited
intertester reliability, while alternative methods of
measurements are generally more difficult to use.
The Iowa ankle range of motion (IAROM) device
was designed in an attempt to develop a simple,
clinically relevant, and time- and cost-effective tool
to measure ankle dorsiflexion range of motion and

TTMETHODS: Validity and intertester reliability of

dorsiflexion range-of-motion measures using the
IAROM device were assessed at 10, 15, 20, and
25 Nm of passively applied dorsiflexion torque,
with both the knee extended and flexed approximately 20°. Stiffness (change in torque/change in
dorsiflexion angle) values were determined using
the angular change obtained between the 15- and

25-Nm torque levels. Convergent validity (n =
12) was assessed through comparison of ankle
dorsiflexion angles measured simultaneously with
the IAROM device and an optoelectronic motion
analysis system. Intertester reliability (n = 17) was
assessed by 2 testers who took measurements
within the same day.

TTRESULTS: Validity testing demonstrated excel-

lent agreement (intraclass correlation coefficient
[ICC] values ranging from 0.95 to 0.98). Reliability
testing demonstrated good to excellent intertester
agreement (ICC values ranging from 0.90 to 0.95).
The ICCs for ankle joint dorsiflexion stiffness were
.71 and .85 for the knee in an extended and flexed
position, respectively.

TTCONCLUSION: The IAROM device provides valid
and reliable measurement of ankle dorsiflexion
ROM. The IAROM device also allows calculation
of stiffness by measuring ROM at multiple torque
levels, although the reliability of the measurement is not optimal. J Orthop Sports Phys Ther
2011;41(4):274-280. doi:10.2519/jospt.2011.3397

TTKEY WORDS: IAROM, plantar flexors, stiffness,
talocrural joint

the functional consequences of relatively
small changes in ankle ROM. Treatment strategies ranging from stretching
exercises to surgical lengthening of the
gastrocnemius-soleus complex are prescribed based on assessments of dorsiflexion ROM, despite the less-than-adequate
reliability of these assessments.5,9,20,22,35
Recent research has identified the importance of being able to accurately measure
relatively small changes in ankle ROM to
accurately identify impairments.8,17,24,34
Currently used methods to obtain ankle
ROM may be broadly classified into 3
categories: goniometry (based on tester’s
perception of end feel),6,9 weight-bearing
(based on the individual’s perception of
end feel),4,21 and instrumented (torquereferenced) techniques.3,25,32 The primary
objections to obtaining ROM measures
using goniometry are that it is not adequately reliable, it is tester dependent,
and recording angular displacement
alone does not allow the calculation of
stiffness.9,22,35 Better measures of ankle
dorsiflexion must, therefore, be developed
to allow simultaneous assessment of stiffness and to make appropriate decisions
about treatment options and outcomes.
To address the less-than-optimal reliability and validity of handheld goniometric measurements, several alternative

Director, Military Performance Laboratory, Center for the Intrepid, Brooke Army Medical Center, Fort Sam Houston, TX. 2Assistant Professor, Department of Physical Therapy,
New York University, New York, NY. 3Research Assistant, Graduate Program in Physical Therapy and Rehabilitation Science, The University of Iowa, Iowa City, IA. 4Professor and
Chairman, Department of Orthopaedics, University of Utah School of Medicine, Salt Lake City, UT. 5Associate Professor, Graduate Program in Physical Therapy and Rehabilitation
Science, The University of Iowa, Iowa City, IA. This protocol for this study was approved by The University of Iowa Human Subjects Office, Institutional Review Board. We, the
authors, affirm that we have no financial affiliation (including research funding) or involvement with any commercial organization in any matter included in this manuscript.
This project was supported through departmental funding. Jason Wilken received partial support from the Foundation for Physical Therapy, Inc during the time the study was
completed. Address correspondence to Dr Smita Rao, Department of Physical Therapy, New York University, 380 2nd Ave, 4th Floor, New York, NY. E-mail: smita.rao@nyu.edu

274  |  april 2011  |  volume 41  |  number 4  |  journal of orthopaedic & sports physical therapy

methods of assessing ankle dorsiflexion
ROM have been recently proposed. One
functional approach for assessing ankle
ROM has been to ask patients to perform a controlled lunge.4,21 While this
approach has been shown to be reliable,4
weight-bearing methods of assessing dorsiflexion may have limited applicability
in certain clinical situations, such as the
early phases of ulcer healing or in postsurgery or conditions in which weight
bearing is restricted.
An alternative, relatively direct method of assessing ankle dorsiflexion ROM
has been to photograph the foot and leg
as a given force is applied to the metatarsal heads, then to measure the orientation
of the foot relative to the leg.18 Beyond the
practical difficulties of applying this technique in a clinic, failure to stabilize the
foot and the localized application of force
may not adequately replicate loading of
the foot during functional tasks. Computerized approaches that isolate ankle joint
motion and measure the applied external
torque, making it possible to measure
not only ankle ROM but ankle stiffness
(changes in ankle dorsiflexion angle as
a function of applied external torque),
have also been proposed.3,7,8,10,32 However, the increased accuracy of these more
sophisticated measurement approaches
comes at a financial cost. These systems
also tend to be difficult to transport and
complicated to use, raising questions as
to their clinical usefulness and cost effectiveness. Most importantly, few of these
ROM devices have demonstrated reliability,4,18 and none, to our knowledge,
has demonstrated validity. Further, while
most studies report ankle ROM data
from an average of 3 readings, none has
quantified the potential benefit of single
versus average measures of ROM.
Given the shortcomings of these previous techniques, the Iowa ankle range of
motion (IAROM) device was designed in
an attempt to develop a simple, clinically
relevant, and time- and cost-effective
measurement technique. The purpose
of this project was, first, to assess intratester reliability of single versus average

FIGURE. The Iowa ankle range of motion testing
device positioned with the knee flexed. Key features
of the device include the ability to alter knee flexion
angle (A) and device axis of rotation (B), as well as
determine angular displacement (C) at known torque
levels (D).

measures (as to answer the question,
“Do I need to take and average of 3 measures, or is 1 sufficient?”) and, second, to
determine the intertester reliability and
convergent validity of measures obtained
with a new, portable, practical, and costeffective device for testing ankle dorsiflexion ROM and stiffness.



his study was approved by The
University of Iowa Institutional
Review Board for Experimentation
on Human Subjects, and consent was
obtained from all participants. For validity testing, 12 participants (6 male, 6
female; mean  SD age, 23  3 years;
height, 1.7  0.1 m; body mass, 72  12
kg) were simultaneously evaluated using
the IAROM device and a motion analysis system (Optotrak 3020; Northern
Digital Inc, Waterloo, ON, Canada). To
evaluate intertester reliability, dorsiflexion ROM was assessed in 17 participants
(7 male, 10 female; mean  SD age, 52 
15 years; height,1.7  0.1 m; body mass,
88  21 kg). Patients receiving orthopaedic care for unilateral foot or ankle injury
or pathology at the University of Iowa
Hospitals and Clinics were recruited to
participate in the study. The limb contralateral to the one requiring orthopaedic
care was tested.

The IAROM device (FIGURE 1) was de-

signed to be easy to assemble, inexpensive to produce, and easy to use. The
device consisted of a 30-by-30-cm Plexiglas footplate, attached to a 30-by-40cm base plate. Two 10-cm-wide Velcro
straps, passed through lateral slots in
the base plate, secured the lower leg during testing. A 3-cm-high semirigid foam
block was placed under the distal leg to
support the tibia in a position perpendicular to the foot plate. Adjustable supports
on the proximal end of the device allowed
knee flexion angle to be increased to approximately 20° during testing.

Participants were positioned in the device with the long axis of their tibia perpendicular to the foot plate, with the foot
vertical and the sole in contact with the
transparent Plexiglas foot plate. The axis
of rotation of the device was then adjusted in the anterior/posterior and superior/
inferior directions to approximate the
ankle axis of rotation, as determined by
palpation of the distal tips of the medial
and lateral malleoli.12 To ensure that the
participant was properly aligned in the
device, to precondition the soft tissue,
and to minimize potential measurement
variability due to previous activity, 25
Nm of external dorsiflexion torque was
applied approximately 20 times prior to
testing. The rate of external torque application was kept extremely low to replicate
the quasi-static testing procedures used
clinically6 and to avoid eliciting a stretch
reflex. The total time for each torque repetition took up to 5 seconds.
Angular measurement was performed
using a digital inclinometer (Checkpoint
Inc, Torrance, CA), zeroed on the middle
third of the tibial crest to provide a consistent anatomical reference point (perpendicular to the crest was used as 0°
dorsiflexion) and then mounted on the
foot plate. The moment of force (torque)
about the ankle joint was controlled by
applying 45, 67, 89, and 111 N of force (10,
15, 20, and 25 lb of force) perpendicular
to the foot plate with a handheld force
gauge (FDK 40; Wagner Instruments,

journal of orthopaedic & sports physical therapy  |  volume 41  |  number 4  |  april 2011  |  275



technical note


Intrarater Reliability of Single Versus the Average of 3 Measures and 95%
Confidence Intervals for Ankle Dorsiflexion Measured by the 2 Raters
10 Nm

15 Nm

20 Nm

25 Nm

Single measure
Rater 1

0.964 (0.859, 0.990)

0.978 (0.883, 0.995)

0.988 (0.898, 0.997)

0.992 (0.957, 0.998)

Rater 2

0.946 (0.775, 0.985)

0.985 (0.882, 0.987)

0.963 (0.906, 0.988)

0.988 (0.946, 0.997)

Average of 3 measures
Rater 1

0.988 (0.948, 0.997)

0.992 (0.920, 0.998)

0.996 (0.963, 0.999)

0.997 (0.985, 0.999)

Rater 2

0.981 (0.912, 0.995)

0.985 (0.933, 0.996)

0.987 (0.967, 0.996)

0.996 (0.981, 0.999)

Greenwich, CT) at a distance of 22.5 cm
from the axis of rotation. Testing was performed by using one hand to apply the
external torque, and placing the other
hand on the participant’s lower leg to palpate for any muscle activation and ensure
participant relaxation. The sequential application of external dorsiflexion torque
from 10 to 25 Nm was considered a single
trial. Following 3 trials, with the knee in
an extended position, the device was inclined to approximately 20° of knee flexion. Flexing the knee reduced the ability
of the bi-articular gastrocnemius to passively resist dorsiflexion of the ankle
relative to the unaffected mono-articular
soleus muscle. Inclination of the IAROM
base alters the orientation of the tibia,
which serves as the reference point for
calculating ankle position. To account for
this change in position, the inclination of
the tibial crest was remeasured with the
digital inclinometer.

Reliability Testing
To evaluate intertester reliability, participants were tested by a physical therapist and a research assistant who was
trained in the use of the measurement
system but had no previous experience
in ROM assessment. Training for the inexperienced tester consisted of a total of
approximately 1 hour of data collection,
under direction, and discussion of proper
alignment and data recording using the
device. Same-day reliability testing was
performed such that tester order alternated with each consecutive participant
to minimize any potential order effect.
To assess intratester reliability of single

versus average measures, each tester
performed 3 consecutive trials (each including all 4 force levels), first with the
knee extended, then repeated the testing
with the knee flexed. Testing was then
performed by the second tester, after the
device was completely removed and reset
so that cues could not be taken from prior

Validity Testing
For validity testing, ankle dorsiflexion motion was simultaneously evaluated using the IAROM device and an
optoelectronic motion analysis system
(Optotrak 3020; Northern Digital, Inc,
Waterloo, ON, Canada). Three markers
on the tibial crest and 3 markers on the
foot (fifth metatarsal, dorsum, and lateral
heel) were used to generate a rigid-body
representation for both segments, to
determine the dorsiflexion angle of the
foot relative to the tibia. Markers were
placed over bony areas, where movement of underlying soft tissue could be
minimized, to provide accurate measures
of ankle ROM. Simultaneous measurements of ankle dorsiflexion ROM were
acquired with the IAROM device and
motion analysis system for 3 trials (all 4
force levels) at each of the 2 knee flexion
angles. Using motion analysis as a reference, we assessed the convergent validity
of our dorsiflexion ROM measures using
the IAROM.

Controlling for Bias
We controlled for selection bias by recruiting a random selection of patients
who were seeking care from a foot and

ankle orthopaedic specialist. Both the
digital inclinometer and handheld dynamometer in the IAROM device can be zeroed to a person’s specific reference prior
to starting data collection, thus eliminating the introduction of calibration errors
or instrument bias. Expectation bias was
minimized by having the testers use the
device in random order, and by blinding
the second tester to the measures obtained by the first tester. Verification bias
was minimized by testing the contralateral ankle of patients who were seeking
care from an orthopaedic foot and ankle
specialist, and by not restricting recruitment to patients with a specific pathology
or diagnosis. In addition, bias was minimized through randomization, blinding, prospective design, and consecutive

Dependent Variables
Ankle dorsiflexion angle values were recorded for each force application level.
Stiffness was computed as change in
torque divided by change in ankle dorsiflexion angle over the 15-to-25-Nm interval. The 15-to-25-Nm torque interval was
selected for calculating stiffness to avoid
the more nonlinear “toe” region that exists at lower torque levels.19

Data Analysis
Mean, SD, and standard error of the
measurement (SEM) were used to summarize dependent variables. SEM was
calculated as follows: SEM = SD × (1 –
r)1/2, where r is the reliability coefficient.
The 90% confidence bound of the minimal detectable change (MDC90) was used

276  |  april 2011  |  volume 41  |  number 4  |  journal of orthopaedic & sports physical therapy


Intertester Reliability of Ankle Range of Motion (deg) and Stiffness  
(Nm/deg) Measurements, With the Knee Extended and Flexed
Mean ± SD

ICC2,1 (95% CI)



Knee extended
Ankle dorsiflexion at 10 Nm

1.0  8.8

0.924 (0.886, 0.961)



Ankle dorsiflexion at 15 Nm

10.5  7.5

0.943 (0.875, 0.967)



Ankle dorsiflexion at 20 Nm

16.9  6.8

0.901 (0.861, 0.922)



Ankle dorsiflexion at 25 Nm

21.2  6.7

0.943 (0.876, 0.984)



0.711 (0.518, 0.852)




1.04  0.15

Knee flexed
Ankle dorsiflexion at 10 Nm

6.6  7.8

0.904 (0.874, 0.954)



Ankle dorsiflexion at 15 Nm

15.6  8.1

0.951 (0.891, 0.970)



Ankle dorsiflexion at 20 Nm

21.3  8.5

0.944 (0.901, 0.972)



Ankle dorsiflexion at 25 Nm

25.7  8.7

0.952 (0.853, 0.990)



0.851 (0.696, 0.921)




1.00  0.18

Abbreviations: CI, confidence interval; ICC, intraclass correlation coefficient; MDC, minimum detectable change; SEM, standard error of the measurement.

to examine clinically relevant change in
peak dorsiflexion. The MDC90 represents
the minimal change that is not due to
measurement error.11 The MDC90 was
computed as the product of SEM, the z
score for the 90% level of confidence, and
√2. Intratester reliability of single versus
average measures was assessed using intraclass correlation coefficients (ICC2,1
and ICC2,3). To assess convergent validity, ICC2,3 was calculated for comparison
between the values obtained with the
IAROM device and those determined via
motion analysis. To assess intertester reliability, ICC2,1 was calculated for each level
of force application. The ability to determine ankle stiffness in a reliable manner
was also assessed using ICC2,1.
In addition to providing mean data
for both ankle ROM and stiffness, rootmean-square (RMS) error was calculated
to provide information regarding the absolute magnitude of difference that can
be expected between methods of testing
or between testers.



ntratester reliability of single
versus the average of 3 measures is
summarized in TABLE 1 and indicates excellent reliability (greater than 0.94) for

single measures.23 Therefore, single measures were used for subsequent analyses.
The mean  SD RMS differences in
peak dorsiflexion between testers at 10,
15, 20, and 25 Nm were 2.5°  0.5°, 2.3°
 0.5°, 2.7°  0.6°, and 2.5°  0.5° with
the knee extended and 2.9°  0.4°, 2.8°
 0.4°, 3.4°  0.4°, and 3.7°  0.3° with
the knee flexed, respectively. Mean  SD,
ICC2,1, SEM, and MDC90 values are presented in TABLE 2, and demonstrate high
levels of intertester agreement. Low SDs
indicate that ankle joint stiffness was
very homogenous within the group of
participants tested. Though intertester
differences were small for the calculation
of ankle joint stiffness, the ICCs (95%
confidence intervals) were 0.711 (0.518,
0.852) and 0.851 (0.696, 0.921) for the
knee extended and knee flexed, respectively (TABLE 2).

For convergent validity, we noted mean 
SD RMS differences in peak dorsiflexion,
at 10, 15, 20, and 25 Nm of 1.7°  0.4°,
1.3°  0.3°, 1.4°  0.4°, and 1.7°  0.4°
with the knee extended and 2.1°  0.3°,
1.8°  0.4°, 1.5°  0.4°, and 1.5°  0.4°
with the knee flexed, respectively, between testing methods. ICC2,3 and 95%
confidence intervals for peak dorsiflexion
measured with the knee extended and

flexed to approximately 20° are summarized in TABLE 3.



he IAROM device was developed
in an attempt to provide a level of
accuracy similar to that of more
technologically advanced ankle ROM
testing systems, while being more affordable and easier to use. We determined
that the IAROM device provides both
valid and reliable assessment of ankle
dorsiflexion ROM. The IAROM’s design
characteristics, which include the application of predetermined levels of external dorsiflexion torque and the ability to
monitor foot positioning and the distribution of surface contact along the sole
of the foot, likely contributed to the high
validity and reliability measures seen in
this study. To our knowledge, this is the
only ankle passive dorsiflexion ROM device that has been evaluated for both reliability and validity.
Preliminary testing with the IAROM
device identified a few difficulties in testing certain populations that are likely
common to other ROM testing methods.
The ability to accurately measure ankle
ROM was compromised in participants
who were morbidly obese (body mass index greater than 50 kg/m2), as it was not

journal of orthopaedic & sports physical therapy  |  volume 41  |  number 4  |  april 2011  |  277



technical note


Convergent Validity of Peak Dorsiflexion, as Determined Using
Optoelectronic Tracking and the Iowa Ankle Range of Motion Device (n = 12)*
10 Nm

15 Nm

20 Nm

25 Nm

Knee extended

0.957 (0.882, 0.973)

0.967 (0.867, 0.997)

0.954 (0.847, 0.983)

0.966 (0.892, 0.979)

Knee flexed

0.971 (0.871, 0.981)

0.968 (0.894, 0.978)

0.967 (0.851, 0.992)

0.977 (0.858, 0.990)

*Values are ICC2,3 and 95% confidence intervals for testing performed with the knee extended and flexed to approximately 20°.

possible to adequately stabilize the leg in
these participants. In addition, a small
subset of participants initially had difficulty relaxing, as detected with palpation
of the dorsiflexor tendons and increased
trial-to-trial variability, and required
some coaching to ensure the absence of
muscle activation. Finally, a few elderly
and frail participants, typically with a
body mass of less than 55 kg, were unable
to tolerate an applied torque of greater
than 20 Nm.
The validity testing demonstrated the
importance of selecting landmarks when
defining segments (APPENDIX). Using the
crest of the tibia, as opposed to the long
axis of the shank, as is typical in goniometric testing, resulted in an offset of approximately 5° between measures, which
has been previously observed by Stebbins
et al.31 After accounting for this offset,
mean values obtained with the knee extended closely matched the goniometric
values reported by Kaufman et al,14 as
well as the device-measured values reported by Moseley et al.18
The IAROM device provided superior
intertester reliability compared to previously reported values (ICCs ranging from
0.50 to 0.80) obtained from goniometric
methods of ankle dorsiflexion ROM assessment.1,2,13-15,20,28 Intertester reliability
noted with the IAROM device was comparable to that of other computerized
systems3,32 and to the weight-bearing
lunge methods.4,21 The poor reliability of
ankle dorsiflexion assessment is problematic when deciding on a treatment or
assessing treatment effects, as it provides
the false perception of intervention effectiveness or obscures actual differences.
The digital inclinometer has a resolution
of 0.1°, and the handheld dynamometer

has a resolution of 0.45 kg (1 lb). Given
the high accuracy of the instruments, we
anticipated that between-trial variability would constitute a greater source of
measurement error. Consistent with this
expectation, we noted an overall intertester reliability of 0.96, SEM of 2°, and
MDC90 of approximately 5°. SEM values
obtained during reliability testing of the
IAROM device were less than a fourth
of those determined in the previously
published goniometric study showing
the best intertester reliability,20 which
underscores the greater precision with
the IAROM. One reason for the better
intertester reliability values reported in
this study may be the IAROM protocol’s
standardized application of external dorsiflexion torque. Such control is likely key
to the collection of reliable and clinically
relevant measures, as this study data and
others18 have shown that a 5-Nm change
in torque can result in a 5° to 10° change
in measured ankle dorsiflexion ROM.
This magnitude of difference can represent as much as 25% of the total motion
available in dorsiflexion. The application
of predetermined torque levels, as compared to determining the torque required
to reach the predetermined dorsiflexion
angle, is also more practical for the assessment of a wide variety of patient populations in which ROM may be limited.
The ability to determine ankle dorsiflexion ROM through a range of predetermined force levels also has the
advantage of documenting ankle stiffness.19,32 Ankle stiffness can be calculated from the dorsiflexion angle change
as a function of applied torque. While
the stiffness values obtained using the
IAROM device are in agreement with
those reported in the literature,27,29,30,33

reliability coefficients were not as high
and had wider 95% confidence intervals
(TABLE 2). For stiffness, we noted low SD
and SEM, as well as low ICC values. This
counterintuitive combination of low SD
and low ICCs may be due to the intrinsic
homogeneity of the stiffness measure in
our sample.23 Consistent with this contention, the intersubject variability in
the stiffness measures was less than 10%
in our sample. Perhaps recruiting participants from a population with greater
variability in stiffness, such as individuals with diabetes or other clinical populations, would result in improved ICC
A limitation of this study was that
the reliability data were not obtained
from ankles with a documented pathology. In our experience, the device has
served well in determining ankle ROM
limitations and changes in joint stiffness in patients with diabetes.25 Further
study in participant groups with differing impairments is needed. As in all
other ROM approaches, the measures
obtained with the IAROM device may
be affected by patients who have foot
or ankle pain and/or muscle splinting.
However, because one hand is free when
obtaining the measures, it is possible
to monitor the soft tissue around the
ankle to detect soft tissue changes. The
acrylic footplate also allows the investigator to monitor changes in foot contact
that might be associated with secondary
compensations. We, therefore, believe
that the reliability demonstrated in this
study substantiates the potential value of
this approach for assessing ankle ROM;
however, as with any other assessment,
tester attentiveness is required to obtain
valid results.

278  |  april 2011  |  volume 41  |  number 4  |  journal of orthopaedic & sports physical therapy



nkle dorsiflexion ROM can be
reliably and validly measured in
clinical or research settings using
the IAROM device. The device’s simple
and relatively low-tech design allows
individuals who have minimal previous
knowledge and skill in range-of-motion
assessment to use the IAROM device to
determine ankle dorsiflexion ROM, with
little training, and to do so with a higher
level of reliability and confidence than is
possible with conventional goniometry. t






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journal of orthopaedic & sports physical therapy  |  volume 41  |  number 4  |  april 2011  |  279


technical note



The standard method for measuring ankle dorsiflexion using a goniometer
uses the fibula as a reference for the stationary arm and the plantar aspect
of the heel or fifth metatarsal for the moving arm (solid black lines). The Iowa
ankle range of motion device uses the tibia crest as a reference (dashed black
line), similar to the reference used by Stebbins et al, 31 and the plantar aspect
of the foot for the moving arm. The angular difference between using the lateral aspect of the fibula versus the tibial crest as a reference is approximately
5°. The offset does not affect our measurements but helps in interpreting our
results relative to those reported in the literature.

This image depicts the Iowa ankle range of motion device setup and the
position of the tibial crest, with the knee extended (solid line) and knee flexed
(dashed line). Position of the tibia relative to the device does not change.
However, change in inclination of the IAROM base flexes the knee by about
20° and also changes inclination of the tibial crest relative to the foot plate.

280  |  april 2011  |  volume 41  |  number 4  |  journal of orthopaedic & sports physical therapy

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