Reliability of Goniometric Measurements and Visual
Estimates of Knee Range of Motion Obtained in a
Clinical Setting
Michael A Watkins, Dan L Riddle, Robert L Lamb and
Walter J Personius
PHYS THER. 1991; 71:90-96.
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Research Report
Reliability of Goniometric Measurements and
Visual Estimates of Knee Range of Motion
Obtained in a Clinical Setting
The purpose of this study was to examine the intratester and intertester reliability
for goniometric measurements of knee flexion and extension passive range of
motion (PROM). In addition, parallel-forms reliabilityfor PROM measurements of
the knee obtained by use of a goniometer and by visual estimation was examined. The intertester reliabilityfor visual estimates of the PROM of the knee was
also examined. Repeated measurements were obtained o n 43 patients in a clinical setting. The intraclass correlation coeficients (ICCs)for intratester reliability of
measurements obtained with a goniometer were .99forflexion and .98for extension. Intertester reliabilityfor measurements obtained with a goniometer was .90
f o r m i o n and .86for extension. The ICCs forparallel-fom reliabilityfor measurements obtained with a goniometer and by visual estimation ranged from .82
to .94. The intertester reliabilityfor measurements obtained by visual estimation
was .83for flexion and .82for extension. Results suggest clinicians should use a
goniometer to take repeated PROM measurements of a patient's knee to minimize
the error associated with these measurements. (Watkins MA, Riddle DL, Lamb RL,
Personius WJ Reliability of goniometric measurements and visual estimates of
knee range of motion in a clinical setting. Pips Ther. 1991;71:90-9 7.1
Michael A Watklns
Dan L Riddle
Robert L Lamb
Walter J Personius
Key Words: Kinesiolo~/biomechanics,lower extremity; Lower extremity, knee;
Tests and measurements, range of motion.
Physical therapists frequently assess
passive range of motion (PROM) of
the knee as part of their examination
of patients with knee complaints. The
universal goniometer is frequently
used to measure PROM of the knee.
M Watkins, MS, PT, is Director of Physical Therapy, Glens Falls Hospital, 100 Park St, Glens Falls,
NY 12801 (USA). This study was completed in panial fulfillment of the requirements for Mr Watkins's Master of Science Degree in Physical Therapy. Department of Physical Therapy, School of
Allied Health Professions, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA. Address all correspondence t o Mr Watkins.
D Riddle, MS, PT, is Assistant Professor, Department of Physical Therapy, School of Allied Health
Professions, Medical College of Virginia, Virginia Commonwealth University, PO Box 224, MCV Station, Richmond, VA 23298.
R Lamb, PhD, PT, is Associate Professor and Chairman, Depanment of Physical Therapy, School of
Allied Healtk. Professions, Medical College of Virginia, Virginia Commonwealth University.
W Personius. PhD, PT, is Professor and Chairman, Department of Physical Therapy, Shenandoah
College and Conservatoly-Winchester Medical Center, Winchester, VA 22601.
This study was approved by the Institutional Review Board at Virginia Commonwealth University.
Many times, however, a visual estimation of the PROM is made in lieu of
using a goniometer. If PROM measurements are to be useful to the
physical therapist, the reliability of the
measurements must be established.
Reliability is defined as the consistency of a measurement.' Because
PROM measurements are taken on a
patient several times, and often by
different therapists, intratester and
intertester reliability are essential if
the measurements are to be
meaningful.'
Few studies have examined the reliability for PROM measurements of the
knee taken in a clinical setting.
Rothstein and colleagues3 examined
This article was submitted May 18, 1990, and was accepted September 24, 1990.
Physical Therapy /Volume 71, Number 2 /February 1991
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90 / 15
the intratester and intertester reliability of PROM measurements taken on
12 patients' knees. Twelve randomly
paired physical therapists measured
passive knee flexion and extension on
patients who required knee PROM
measurements as part of their physical therapy examination. Therapists
were allowed to use their own techniques while taking measurements.
The authors reported good intratester
reliability for measurements of flexion
and extension and good intertester
reliability for flexion measurements.
Intertester reliability for knee extension measurements was reported as
being poor.
Apost hoc analysis revealed intertester
reliability for knee extension measurements improved when paired
therapists used the same patient position during the measurements. This
finding suggests patient position
needs to be controlled during knee
extension measurements to minimize
error. However, as the authors indicated, because the study was done in
one clinical setting on a small sample,
the results may not be generalizable
to other clinics.
Based on our experience, therapists
frequently visually estimate the PROM
of their patients' knees. Therapists
also may take goniometric measurements and visual estimates of a patient's knee PROM during the course
of treatment. Goniometry and visual
estimation of a patient's range of motion (ROM) are parallel forms of the
same test. Parallel-forms reliability is
determined by comparing the measurements taken with two methods
and describes the extent to which
measurements obtained with two
methods are interchangeable.4 The
parallel-forms reliability for goniometric measurements and visual estimates
of the PROM of the knee has not
been examined.
Opinions regardng the usefulness of
visual estimates of PROM vary. The
American Academy of Orthopaedic
Surgeons (AAOS)5 and Rowe6 have
suggested that visual estimation is
more accurate than using a goniometer to measure ROM when bony land-
marks are not easily seen or palpated.
By contrast, Moore,' Minor and Minor: and Salter9 have stated that goniometric measurements are more reliable than visual estimates. None of
these authors provided data to support their arguments.
There has been only one study that
has examined the reliability of visual
estimates of PROM of the knee. Marks
and associates1° investigated the reliability for visual estimates of knee
ROM taken by three physicians on
rheumatoid arthritic patients. Marks et
a1 reported good intratester and intertester reliability. Although this
study was done in a clinical setting,
the measurements were obtained by
physicians, which may not reflect the
reliability of measurements taken by
physical therapists.
The reliability for visual estimates of
knee PROM has not been examined
in a physical therapy setting. In addition, the parallel-forms reliability of
goniometric measurements and visual
estimates of the PROM of the knee
has not been examined. Finally, even
though Rothstein et a13 reported the
reliability for goniometric PROM measurements of the knee taken on patients, the sample size was small. A
study that examines the reliability of
goniometric measurements and visual
estimates of knee PROM obtained on
a large sample of patients would further elucidate the usefulness of these
measurements.
Our study was divided into two parts.
Part 1 was designed to replicate part
of the study of Rothstein et al? but to
use a different statistical test. Rothstein
et a13 used a less conservative form of
the intraclass correlation coefficient
(ICC), which, we believe, underestimates error.11 In part 1,we examined
the intratester and intertester reliability for goniometric PROM measurements of the knee. The purpose of
pan 2 of our study was to examine
the parallel-forms intratester reliability
for goniometric measurements and
visual estimates of knee flexion and
extension. In addition, the parallelforms intertester reliability of goniometric measurements and visual esti-
mates of the knee was examined. The
intertester reliability for visual estimates of knee flexion and extension
was also examined. Because we believed that therapists would likely be
biased by their first measurements,
we chose not to examine the intratester reliability for visual estimates of
the knee.
Method
Subjects
Subjects for this study were 43 patients referred to the Physical Therapy
Department, Medical College of Virginia Hospital (MCVH), Virginia Commonwealth University, Richmond, Va.
Criteria for admission to this study
were that each patient was at least 18
years of age and that the patient's examination would normally include
PROM measurements of the knee.
Both knees of 7 of the 43 patients
were measured; therefore, a total of
50 sets of measurements were
obtained.
The subjects consisted of 29 males
and 14 females. The ages of the subjects ranged from 18 to 80 years @=
39.5, SD=15.0). Age, sex, height,
weight, diagnosis, and extremity
tested were recorded for each subject
(Tab. 1). These data were collected
for a posteriori analyses to determine
whether any of these factors may have
influenced reliability. All subjects
signed a consent form prior to participation in the study.
Testers
All testers were full-time staff physical
therapists who treated adult patients
at MCVH. The 14 therapists had a
mean of 7.2 years of experience (SD
=4.0) and had graduated from 12
different physical therapy schools. Additional information collected was the
age, sex, area of specialty, and the
number of times per week each therapist visually estimated the PROM of
the knee and recorded the value on
the chart (Tab. 2). These factors were
collected for a posteriori analyses to
determine whether any of these variables may have influenced reliability.
Physical Therapy /Volume 71, Number 2/February 1991
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%
Table 1
. Characteristics of Patient Sample (N=43)
Variable
Number of subjects
Male
Female
therapist was given a different random
list of names of the other therapists.
When a therapist identified a patient
as being appropriate for the study,
that therapist would take the first set
of measurements. The second tester
was then determined from the first
tester's random list. This method provided a random pairing of therapists
for each patient admitted to the study.
Age (Y)
x
A recorder (MAW) was responsible
for reading and recording all measurements and for recording the patient position used for each measurement. Patient position was recorded
for a posteriori analyses to determine
whether positioning influenced
reliability.
SD
Range
Weight (kg1
X
SD
Range
Height (cm)
X
SD
Range
Number of right knees measured
Number of left knees measured
Diagnostic categories
" Fractures
(2) o r other injury (1) not requiring surgery.
Arthroscopies (1 I), anterior cruciate ligament reconstructions (5),fractures ( 4 ) , knee replacement
(I), medial collateral ligament repair ( I ) , osteochondroma excision (1).
'Head injuries ( 5 ) , spinal cord injury (I), cerebrovascular accident ( I ) , nlultiple sclerosis (1).
'Hemophilia (6), rheumatoid arthritis (I), diabetes (I), burns (1)
'Below-knee amputees.
Instrumentation
Three plastic goniometers,* each with
a 12.7-cm (5-in) moveable arm and a
scale marked in 1-degree increments,
were used to take measurements. We
chose this size of goniometer because
we believe these types of goniometers
are frequently used on patients with
knee problems. The accuracy of each
goniometer was assessed prior to the
beginning of the study by measuring
10 randomly selected angles drawn by
use of a protractor. The three goni-
ometers measured all angles accurately. The goniometer scales were
covered with contact paper on the
side facing the testers so they could
not read the measurements. The
other side was left uncovered, which
allowed the recorder to read the
measurements.
Procedure
The procedure chosen for this study
was a modification of the procedures
described by Rothstein et al.3 Each
'ConvaCare Inc, PO Box 19747, Raleigh, NC 27619.
Physical Therapy /Volume 71, Number 2 /February 1991
When an appropriate patient was
identified, the therapist who identified
the patient (the referring therapist)
notified the recorder. The recorder
then identified the second tester by
proceeding down the random list of
the referring therapist to the name of
the next available therapist. The referring therapist first visually estimated
the PROM of the knee flexion and
extension, in that order. Visual estimates were done first because we felt
that if the goniometer was used first,
the angle made by the goniometer
arms might influence the visual estimate. The therapist recorded the measurements on a piece of paper provided by the recorder and then
handed the paper to the recorder.
The referring therapist then used the
blinded goniometer to measure passive knee flexion twice and knee extension twice, in that order. When the
arms of the goniometer had been
aligned to the therapist's satisfaction,
the goniometer was handed to the
recorder. The recorder read the value
from the goniometer and recorded
the value. After recording each measurement, the recorder positioned the
goniometer arms back to the zerodegree position. After each measurement, the subject's limb was repositioned in its starting position.
After the referring therapist obtained
the six measurements, the second
tester (retest therapist) took the six
measurements in the same order as
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-
calculated by comparing the first and
second goniometric measurements
taken by each tester. The referring
therapists and the retest therapists
each obtained 50 paired measurements for each motion; therefore, a
total of 100 paired measurements
were obtained for each motion. The
ICCs for intertester reliability for goniometric measurements of knee flexion and extension were calculated by
comparing the first goniometric measurements for each pair of testers.
Table 2. Characteristics of
Participating Therapists (N=14)
Variable
Range
Experience (y)
X
Range
MCVHa experience (y)
K
SD
Range
Visually estimateb 1 timelwk
Visually estimate >1 timelwk
Did not visually estimate
Therapist specialty
General
Orthopedic
-
" Medical College of Virginia Hospital
Number of times per week a therapist reported visually estimating knee passive range
of motion and recording the value on the
chart.
the referring therapist. To minimize
bias, the retest therapist did not observe the referring therapist taking
measurements. Throughout the study,
all therapists were allowed to use
their own methods for positioning the
patient and the goniometer.
Part 2. The ICCs for parallel-forms
intratester reliability for measurements obtained by use of a goniometer and by visual estimation were calculated by comparing the visual
estimate and the first goniometric
measurement obtained by each tester.
The ICCs for parallel-forms intertester
reliability for measurements obtained
by use of a goniometer and by visual
estimation were calculated in the following way. The visual estimates obtained by the referring therapists
were compared with the first goniometric measurements obtained by the
retest therapists. In addition, the first
goniometric measurements obtained
by the referring therapists were compared with the visual estimates obtained by the retest therapists. The
referring therapists and the retest
therapists each obtained 50 paired
measurements for each motion; therefore, a total of 100 paired measurements were obtained for each motion.
The ICCs for intertester reliability for
visual estimates of knee flexion and
extension were calculated by comparing the visual estimates for each pair
of testers. Therefore, there were 50
pairs of measurements for each
motion.
Results
The means, standard deviations, and
ranges for all goniometric measurements and visual estimates obtained
in this study are summarized in
Table 3.
Part 1
The ICCs for intratester reliability of
measurements obtained with a goniometer were .99 for knee flexion and
.98 for knee extension. The ICC values for intertester reliability of measurements obtained with a goniometer were .90 for knee flexion and .86
for knee extension (Tab. 4).
Table 3. Range-of-Motion Measurements and Visual Estimates (in Degrees) of
Involved Knees of Patients (N=50 Knees)
Tester 1
Measurement
TZ
Tester 2
SD
Range
-
Data Analysis
The ICC (1,1), as described by Shrout
and Fleiss,lZ was used to describe the
degree of reliability of the measurements. We chose this form of the ICC
because we believe it best reflects the
error that can be expected when a
therapist takes a PROM measurement
on a patient."
-
%
- -
SD
-
Range
-
VE flexiona
104
31
35-1 55
108
30
40-1 75
Gon flexion l b
107
26
43-1 49
105
26
46-1 51
Gon flex~on2"
108
26
44-1 49
105
26
49-1 54
VE extensiond
- 10
13
-45-1 0
-12
17
- 75-0
Gon extension 1"
-12
14
-50-7
-13
16
-65-2
Gon extension 2'
-13
15
-5L11
-13
17
-67-1
-
" VE flexion=visual
-
-
estimate for flexion.
Gon flexion 1 =first goniometric measurement for flexion.
'Gon flexion 2=second goniometric measurement for flexion.
Part 1. The ICCs for intratester reliability for goniometric measurements
of knee flexion and extension were
18/93
extension=visual estimate for extension.
" Gon extension 1 =first goniometric measurement for extension.
Gon extension 2=second goniometric measurement for extension.
Physical Therapy /Volume 71, Number 2 /February 1991
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Part 2
The ICC values for the parallel-forms
intratester reliability of goniometric
measurements and visual estimates
were .93 for flexion and .94 for exten.
sion. The ICC values for the parallelforms intertester reliability of goniometric measurements and visual
estimates were .86 for flexion and .82
for extension. The ICC values for intertester reliability of visual estimates
were .83 for knee flexion and .82 for
knee extension (Tab. 4).
Part 1
Goniometric PROM measurements of
knee flexion and extension were
highly reliable when the same therapist took repeated measurements.
This finding of high intratester reliability for goniometric measurements
of knee flexion and extension agrees
with the results of Rothstein et al.3
The intertester reliability for goniometric measurements of knee flexion
and extension was also high, but not
as high as intratester reliability. To
minimize error, PROM measurements
of the knee should be taken on a patient by the same therapist. Although
the additional error associated with
measurements taken by different therapists is small, this small increase in
error may affect the usefulness of
these measurements.
Rothstein et a1 reported "relatively
poor intertester reliability"3@lG13)
for
goniometl-ic PROM measurements of
knee extension, with ICCs ranging
from .59 to .80. Our study demonstrated higher intertester reliability for
knee extension measurements (ICC =
86). The larger sample size could
explain the higher intertester reliability estimate for knee extension measurements. It has also been suggested
that the reliability for measurements
obtained at one facility may not be
eenera1ize:d to all facilities.3J3 Both
"
studies, however, were in agreement
that the reliability of knee extension
measurements was lower than for
knee flexion measurements.
Rothstein et a13 used formula (E4) of
the ICC described by Bartko and Carpenter,l* which is less conservative
than the ICC (1,l) used in our study.l5
Therefore, relative to our study, the
results obtained by Rothstein et a1
provided an overestimation of the
degree of reliability. The results of
our study, however, demonstrated
similar or higher reliability estimates
compared with those reported by
Rothstein et al.
ability for some measurements.3
Rothstein et a13 demonstrated that the
intertester reliability for knee extension PROM measurements noticeably
decreased when different patient positions were used by both therapists. An
a posteriori analysis of our study
demonstrated that the intertester reliability for goniometric measurements
of knee extension decreased only
slightly when patient position was
different for paired therapists (Tab. 5).
The error associated with knee extension measurements was also slightly
Patient positioning has been considered a factor that may influence religreater when paired therapists used
different patient positions during measurements (Tab. 5). This finding is
different from that of Rothstein et a1
and
suggests that patient position durTable 4. Intratester and Intertester
ing
knee
extension PROM measureReliability for Knee Flexion and
ments contributes only slightly to the
Extension Measurements
error associated with these measurements. Although the error associated
lntratester Intertester
with using different patient positions
-Method
N" ICCb N ICC
during knee PROM measurements is
only slightly greater than the error
present when the same position is
Flexion
used, we recommend standardizing
Goniometer
100 .99
50 .90
patient position to minimize error.
Visual estimation
... ...
50 .83
-
Between methodsC 100
.93
100
.86
Part 2
The parallel-forms intratester reliability for PROM measurements obtained
by use of a goniometer and by visual
estimation was high for knee flexion
and extension measurements. The
reliability, however, was not as high
as the intratester reliability for goniometric measurements of knee flexion
Extension
Goniometer
100
.98
50
.86
Visual estimation
...
...
50
.82
100
.94
100
.82
-
Between methods
a
N=number of paired measurements.
ICC=intraclass correlation coefficient (1,l).
'Visual estimate was compared with first goniometric measurement for each tester.
Table 5. Intertester Reliability When Paired Testers Used the Same and Dzfferenl
Patient Positions
ICC'
Jolnt
Motion
N
Posltlon
Gonlometer
Flexion
35
Same
.92
15
Different
.85
38
Same
.87
12
Different
.84
Extension
a
Visual
Estlmatlon
ICC=intracIass correlation coefficient (1,l).
N=number of paired therapists.
Physical Therapy/Volume 71, Number 2 /February 1991
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94 / 19
and extension. Interchanging goniometric measurements and visual estimates of knee flexion o r extension,
therefore, may introduce a small
amount of additional error. A therapist's ability to detect changes on the
order of a few degrees, on average,
may be compromised when visually
estimating a patient's PROM. The additional measurement error could result
in a therapist making an incorrect
decision when assessing for a small
change in a patient's PROM.
Table 6. Intratester and Intertester Reliability for Measurements Obtained from
Patients Representing Dgerent Diagnostic Categories
Flexlon
Diagnostlc
Category
N"
Goniorneter
Extension
VEb
Between
Methodsc
Gonlorneter
VE
Between
Methods
Nonsurgical
lntratester
6
lntertester
3
Surgical
The parallel-forms intertester reliability for PROM measurements obtained
by use of a goniometer and by visual
estimation was fair for knee flexion
and extension measurements. The
intertester reliability for goniometric
measurements was slightly higher
than the parallel-forms intertester reliability for these measurements. When
different therapists must measure a
patient's knee PROM, error can be
minimized if both therapists use a
goniometer.
lntratester
46
lntertester
23
Neurological
lntratester
18
lntertester
9
Medical-surgical
lntratester
18
lntertester
9
Amputees
lntratester
12
lntertester
6
N=number of paired measurements
The intertester reliability for measurements of knee flexion and extension
obtained by visual estimation was fair,
but better than we expected. Based
on our clinical experience, we would
have expected lower reliability. This
finding, that different therapists can
fairly reliably estimate knee ROM, is
in general agreement with the findings of Marks and colleagues.1° However, the intertester reliability for goniometric measurements was higher
than for visual estimates of knee flexion and extension. Therapists will
minimize error in their measurements if they take measurements on a
patient with a goniometer. This finding supports claims by Moore,' Minor
and MinoP, and Salter9 that measurements obtained with a goniometer are
more reliable than visual estimates of
PROM.
An a posteriori analysis similar to the
study of Riddle et all3 was performed
to determine the effect of different
diagnoses on reliability (Tab. 6). Patient diagnosis did not appear to affect
intratester reliability, except for
parallel-forms reliability of measurements taken on below-knee amputees.
Visual estimation
Reliability comparing first goniometric measurement with visual estimate. The N for intertester
reliability is equivalent to the intratester reliability for these measurements.
Intertester reliability was generally
poor (ICCs= .03-.76) for measurements taken on below-knee amputees.
Because the involved knees of patients with below-knee amputations
have shorter distal limb segments,
therapists may have difficulty aligning
a goniometer o r estimating the knee's
position during PROM measurements.
The small sample of amputees does
not allow us to make conclusions
about the reliability of PROM measurements taken on these patients. Our
study does suggest that the reliability
for PROM measurements of the knee,
taken on below-knee amputees,
should be investigated further.
This study examined the reliability of
PROM measurements of the knee obtained by use of a goniometer and by
visual estimation. The reliability for
goniometric measurements of the
shoulder, elbow, ankle, and foot have
also been examined on appropriate
patient~.3.~3.~~
However, the reliability
for visual estimates of the PROM present at these joints has yet to be examined. The reliability for goniometric measurements and visual estimates
also needs to be examined for the
wrist, hip, and hand. In addition, an
examination of the reliability for active ROM measurements of joints
measured clinically is needed.
Conclusions
Goniometric PROM measurements of
knee flexion and extension are highly
reliable when taken by the same
physical therapist. Goniometric measurements of the PROM of a patient's
knee taken by different therapists will
not be as reliable as when the same
therapist takes the measurements.
Visual estimates of knee PROM will
add slightly more error to the therapist's measurements than those taken
with a goniometer. The additional
error associated with visual estimates
could affect the usefulness of the mea-
Physical Therapy /Volume 71, Number 2 /February 1991
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surements if a therapist is attempting
to detect small changes in a patient's
different
must
measure a patient's PROM, therapists
can minimize error by using a goniometer and by standardizing patient
position.
Acknowledgments
We would like to thank the entire staff of
the Medical College of Virginia Hospital
Physical Therapy Department, whose efforts made this study possible.
References
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Commentary
We applaud Watkins et al for an excellent contribution to our scientific
body of knowledge. Using a method
originally described in 1983 by
Rothstein et al,' the authors have provided physical therapists with clinically useful information regarding the
reliability of measurements of peripheral joint range of motion (ROM) using convc:ntional goniometric procedures. This study is important because
it replicates, in part, a previous study
that described the intratester and intertester reliabilities of measurements
of passive range of motion (PROM) of
the knee. Watkins et al, however, expanded their current investigation to
include the reliability of PROM measurements of the knee using techniques of visual estimation. Using
controlle~iobservations, the authors
have confirmed the clinical impressions of many, that visual estimation
has greater potential for measurement
error than goniometric techniques
when examiners measure joint ROM
in patients.
A critical review of this article indi-
cates that the investigators were meticulous in describing the characteristics of the subjects and examiners and
in analyzing the data. We were impressed with Table 5, which partitions
the 43 patients into five diagnostic
categories and supplies the reader
with important clinical information.
We have two critical comments that
we would like the authors to consider. First, we believe the intratester
intraclass correlation coefficient (ICC)
values for knee flexion (ICC =.99) and
extension (ICC =.98) are extraordinarily high, if one considers the measurements were obtained on patients
in a busy clinical department and analyzed with a conservative form of the
ICC2 Other investigators3-5 have suggested that peripheral joint PROM
measurements are more difficult to
measure reliably than active ROM
measurements because the stretching
of soft tissue structures at end ranges
is dependent on the force the exam-
Physical 'Therapy /Volume 71, Number 2 /February 1991
iner applies to the limbs. We believe
the small amount of intratester measurement error reported by Watkins
et a1 may be attributed to the method
used to make the repeated measurements. The time interval between two
successive measures of PROM of knee
flexion or extension was so brief
(perhaps less than 30 seconds) that
the examiner could have retained a
mental image of the joint's first end
point, even though the PROM was
obtained with a blinded hand-held
goniometer. This mental image possibly could guide the examiner's second measurement, resulting in an
underestimation of the true measurement error.
Second, we would suggest that Watkins et a1 specifically define their
ranges of ICC values associated with
high, good, fair, or poor reliability.
Such labels and their associated ICC
values would offer the reader a conventional frame of reference for interpreting the data.
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Reliability of Goniometric Measurements and Visual
Estimates of Knee Range of Motion Obtained in a
Clinical Setting
Michael A Watkins, Dan L Riddle, Robert L Lamb and
Walter J Personius
PHYS THER. 1991; 71:90-96.
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