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J Musculoskelet Neuronal Interact 2017; 17(3):197-208
Original Article
Intertester and intratester reliability of a movement control
test battery for patients with knee osteoarthritis and controls
P.T. Kaukinen1,2, J.P. Arokoski3, E.O. Huber4, H.A. Luomajoki4
1Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland; 2Department of Physical and Rehabilitation Medicine,
Kuopio University Hospital, Kuopio, Finland; 3Department of Physical and Rehabilitation Medicine, Helsinki University Hospital, Helsinki,
Finland and University of Helsinki, Helsinki, Finland; 4Institute of Physiotherapy, School of Health Professions, Zurich University of
Applied Sciences, Winterthur, Switzerland
Introduction
Knee osteoar thritis (OA) is a disease of multifactor ial origin
with pain and disability1-3. It is characterized by unbalanced
equilibrium between dynamic degenerative and regenerative
structural changes seen in all joint tissues around the knee,
including cartilage, bone, synovium, and periarticular soft
tissues4-6. However, the structure-symptom discordance
have been widely noted with approximately 50% of persons
with structural changes in plain radiographs consistent with
OA being asymptomatic3, 5 ,7,8 suggesting that other processes
including peripheral and central neurophysiological
mechanisms contribute to pain and disability9.
Besides muscles strength, other aspects of muscle
functio n are also affected by th e OA disease pr ocess, including
activation patterns and proprioceptive acuity10. A recent
study showed consistent differences in knee proprioception
between groups with and without knee OA across all knee
movement directions (varus, valgus, flexion and extension)11.
In dynamic knee stability during activities movement control
seems to be a critical factor12.
Movement control (MC) is defined as an ability to perform
active movements while remaining balanced alignment of
the body and lower extremities with an appropriate muscle
response13. MC impairment means a reduction of active
control of movement14,15. The underlying hypothesis is that
impaired MC and lack of awareness of maladaptive movement
patterns sustains pain16,17. In acute pain the central nervous
system can change the motor behavior of the body to remove
further threat of tissue damage and to support healing
which has short-term benefits18. However, in the chronic
phase the motor response may be less meaningful with
potential consequences to the quality of movement and load
on tissues, which, for its part, may lead to tissue irritation
and continuous pain18,19. Furthermore, concerning knee OA,
Abstract
Objectives: To develop a test battery of movement control (MC) tests and assess its intertester and intratester reliability.
Methods: 29 subjects with knee OA with mean age of 64.7 (SD 8.7) years and 12 controls without either knee pain or
previous diagnosis of OA (mean age 36.6 (SD 16.2) years) were included. Two experienced physiotherapists rated the
filmed test performance of six MC tests blinded to the patients and to each other on 3-point scale as correct, incorrect
or failed. Weighted kappa coefficient (wK) with 95% confidence interval (95%CI) and the percentage of agreement were
calculated for each test. Results: One-leg stance, one-leg squat 30 degrees and step down tests showed moderate to
excellent inter- and intratester reliability with wK ranging between 0.43-0.85 for intertester and 0.51-0.80 for intratester
reliability. The reliability of the 90 degrees squat test, small squat and step up tests was poor (wK ranging between 0.09-
0.50). Conclusions: One-leg stance test, one-leg squat 30 degrees and step down test are reliable in the subjects with
knee OA and controls. Further studies are needed to evaluate the discriminative validity of the reliable tests.
Keywords: Movement Control, Reliability, Knee, Osteoarthritis
The authors have no conflict of interest.
Correspond ing author: Päivi Kaukinen, Kuopio University Hospital, PL 100,
FIN-70029 KYS, Finland
E-mail: paivi.kaukinen@kuh.fi
Edited by: F. Rauch
Accepted 26 June 2017
Journal of Musculoskeletal
and Neuronal Interactions
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P.T. Kaukinen et al.: Movement control reliability in knee OA
observational data support the importance of loading in the
progression of the disease19.
Several stud ies have assessed the tests of MC of the lum bar
spine22,23, hip24, neck15 or head and eyes coordination25
showing good reliability and validity. It has been suggested
that movement control impairment (MCI) represents a
subgroup of low back pain and that group-specific treatment
interventions may be more efficient than non-specific
interventions26. To our knowledge MC tests have not yet been
investigated in subjects with painful knee OA.
There is no gold standard for MCI assessment in lower
extremities. It has been suggested that the diagnosis of
MCI should be based on the visual observation of active
movements and functional activities in different starting
positions17,27-3 0 . Therefore, we developed a test battery of
six motor tasks. Because clinical tests are vulnerable for
mistakes, bias and different perceptions, it is important to
evaluate their reliability. Thus, the aim of this study was to
assess intertester and intratester reliability of MC tests in
patients with knee OA and subjects without either knee pain
or previous diagnosis of OA.
Materials and methods
Study design
Six active movement control tests were developed
based descriptions by Sahrmann, Cook and Comerford and
Mottram16,17,3 0 , and in accordance with earlier studies in low
back pain23, and intertester and intratester reliability study
was conducted. The test performance by each participant
was filmed in a standardized manner. Two experienced
physiotherapists rated the test performance blinded to
the patients and to each other on 3-point scale as correct,
incorrect or failed. The study was conducted according to
Helsinki Declaration and approved by The Ethics Committee
of Kuopio University Hospital. All participants gave written
informed consent prior enrollment.
Study sample
The sample size requirement for comparing coefficients
of intertester agreement was calculated by selecting the
level of significance as alpha=0.01 and power [beta=0.80]
for testing hypothesis 0 (H0): kappa (k)1 ≥0.4 versus H1: k1
≤0.4, the required sample size for group testing would be
36 cases for good [k index 0.40] strength of agreement31
[31]. The sample size was set as n=40 to cater for a potential
drop- out rate of 10%.
It was considered important to include in to the study
sample subjects who would perform the tests well in order
to increase variability and thus avoid a possible bias of the
results of too many incorrect or failed test performance31.
Twenty-nine (29) subjects with knee OA and 12 volunteers
without either knee pain or previous diagnosis of OA (later in
the text: controls) participated. The inclusion and exclusion
Tabl e 1. Inclusion criteria for knee OA subjects and exclusion criteria for all subjects.
Inclusion criteria for knee OA subjects:
1Pain within and/or around the knee (WOMAC pain subscale for 24 h prior to study entry >0)
2Kellgren-Lawrence 1-4 radiographic knee OA1
3Pain within the last year in and/or around the knee occurring on most days for at least a month
4Age > 18 years
Exclusion criteria for knee OA subjects and controls:
1Other present pain problem or a central or peripheral nervous system condition causing sensory dysfunction (e.g., stroke, multiple
sclerosis, spinal cord disorders or peripheral nerve lesion)
2History of radicular pain from lower back (L3-S1) during the previous year
3History of total arthroplasty of knee or hip joint
4Severe depression or other severe psychiatric disorder
5Indemnity problems
6Cognitive impairment
7Fibromyalgia or other widespread pain disorder
8Any other unstable disease (e.g., cancer, acute trauma or infection)
9Inflammatory arthritis or other systemic connective tissue disease
10 Inability to come to the hospital for evaluations
11 Inadequate knowledge of the Finnish language (inability to understand the standardized instructions)
12 Current use of analgesics or drugs that modify central pain modulation (e.g. tricyclic antidepressants, serotonin-norepinephrine
reuptake inhibitors and gabapentinoids)
13 Inability to be without any pain medication for 24 h before the investigation
1Please, see Materials and methods. The radiographs were evaluated according to Kellgren-Lawrence (K-L) grading in which 0 means no
OA and 4 refers severe OA33.
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P.T. Kaukinen et al.: Movement control reliability in knee OA
criteria are presented in Table 1. Knee OA diagnosis was
based on clinical symptoms and knee radiographs32. The
knee OA subjects were recruited via local primary health care
providers and from the outpatient clinics of orthopaedics and
physical and rehabilitation medicine of Kuopio University
Hospital, and the controls from colleagues, friends and family
members of the research team.
Evaluation of knee radiographs
The standard plain radiograhps from the symptomatic
knee joint(s) were obtained from the knee OA subjects
on clinical basis as a part of usual clinical practise. The
radiographs were evaluated by two readers experienced in
clinical radiographic evaluation (PTK and JPA) according to
Kellgren-Lawrence (K-L) grading in which 0 means no OA and
4 refers severe OA33.
Test protocol
At the beginning of the test visit, the knee OA subjects
completed a validated Finnish version of the Western
Ontario and McMaster Universities Arthritis Index (WOMAC)
questionnaire34, 35. Knee pain severity of both knees was
recorded by using 100 mm visual analogue scale (VAS).
Two trained physicians (PTK and JPA), who were
not involved in test performance rating, performed the
MC testing protocol using standardized instructions
including a demonstration of each test. The standardized
instructions, and criteria for correct, incorrect and failed
performance for the tests are presented in Figures 1-6.
Each test performance was explained and demonstrated
by the examiner (either PTK and JPA) to the subject and
after that the subject was allowed to try the test once
before the actual test performance. The tests were as
follows: small squat to 30 degrees knee flexion (Figure
1), squat to 90 degrees knee flexion (Figure 2), one-leg
stance (Figure 3), small squat on one-leg stance (Figure
4), step up (Figure 5) and step down (Figure 6). The test
performance using both index knee (i.e. more symptomatic
knee in the subjects with knee OA and randomly selected
knee in the control subjects) and contralateral knee (i.e.
less symptomatic or asymptomatic knee) were filmed
except for squat to 90 degrees knee flexion -test in which
the performance was videoed and evaluated from the
side of the index knee and thus the performance of the
contralateral knee could not be assessed. The order of
the tests was randomized for each participant. Half of the
participants were tested by one examiner and the other
half by the other. The same examiner (either PTK or JPA)
videotaped the test performances. Videos were taken
Fi g ure 1. Α-Β. Small Squat to 30 Degrees Knee Flexion (frontal visual evaluation, right and left sides separately). Standardized
instructions: “First, take some steps staying on the place you are standing, and then remain standing on both feet for ward, feet aligned
about hip-width apart. Then from this position, perform a small squat with flexing your knees approximately 30 degrees (so that you
cannot see your foot tips). Repeat the movement four times, and on the fourth squat, please stay in the squat position for ten seconds.”
A) Correct performance (0 points): Pelvis stays horizontal, hips are aligned, knee stays aligned, knee gap is aligned to foot and foot
stays straight. B) Incorrect performance (1 point): Pelvis is not horizontal, hips do not stay symmetrical, knee is giving away and knee
gap is not pointing to the foot but e.g. medially) and foot is giving in (eg. there is a strong pronation).The performance is unsecure. Failed
performance (2 points): the subject cannot perform the movement.
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P.T. Kaukinen et al.: Movement control reliability in knee OA
Figure 2. A-B. Squat to 90 Degrees Knee Flexion (visual evaluation from the side; only the site of the index knee was evaluated).
Standardized instructions: “First, take some steps stationary staying broadside between the lines marked on the floor so that your
more symptomatic (or randomly selected) knee is closest to the videocamera, and then remain standing on both feet forward, feet
aligned about hip-width apart. Then, from this position, perform a squat with shifting your pelvis and hips backwards and downward to
approximately 90 degrees of flexion of the hips and knees so that your fingertips touch the knee caps. The position of the spine should
not change during the movement. Repeat the movement four times, and on the fourth squat, please stay in the squat position for ten
seconds”. A) Correct performance (0 points): Hip is flexing without flexion of the lumbar spine. There is 90 degrees flexion in both hip and
knee joints. Movement is easy. B) Incorrect performance (1 point): Lumbar spine is flexing strongly. There is not enough flexion in the hip
or knee joint but both joints flex at least 30 degrees. Failed performance (2 points): There is not at least 30 degrees flexion in the hip or
knee joint, or the subject cannot perform the movement.
Figure 3. A-B. One-Leg Stance (frontal visual evaluation, right and left sides separately). Standardized instructions:”First, stand between
the lines marked on the floor facing forward (towards the videocamera), feet aligned about hip-width apart. Then perform a one-leg stance
with your right leg (the left foot has to be entirely lifted in the air) for ten seconds. The pelvis and the upper part of the body should not
move and stay straight. Afterwards the test is performed with your left leg”. A) Correct performance (0 points): Stance is stable and easy.
Alignment of the hip, knee and foot are good (no varus or valgus). No compensating movements. B) Incorrect performance (1 point):
Insecurity or helping with hands in the air. Pelvis does not stay horinzontal. Alignment of the hip, knee or ankle/ foot is not good (eg. there
is varus or valgus in the knee, or the hip is tilting in adduction or the foor is giving in). The subject is tipping slightly to the ground with other
foot. Failed performance (2 points): The subject cannot perform the movement or cannot stay on one leg for at least 5 seconds.
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P.T. Kaukinen et al.: Movement control reliability in knee OA
Figure 4 . A-B. Small Squat o n One-Leg Sta nce (frontal visua l evaluation, r ight and lef t sides separa tely). Standardized i nstruction s:”First,
stand between the lines marked on the floor facing forward (towards the videocamera), feet aligned about hip-width apart. Then, from
this position, take a one-leg stance position with your right leg (lifting your left foot entirely in the air) and perform a small squat with
flexing your knee approximately 30 degrees (so that you cannot see your foot tip). The pelvis and the upper part of the body should not
move and stay straight. Repeat the movement four times, and on the four th squat, please stay in the squat position for ten seconds.
Afterwards the test is performed with your left leg”. A) Correct performance (0 points): Movement is stable and easy. Alignment of the
hip, knee and foot are good (no varus or valgus). There are not compensating movements. B) Incorrect performance (1 point): Insecurity
or helping with hands in the air. Pelvis does not stay horinzontal. Alignment of the hip or knee or an kle / foot is not good (eg. there is varus
or valgus in the knee or the hip is tilting in adduction or the foot is giving in). The subject is tipping slightly to the ground with other foot.
Failed performance (2 points): The subject cannot perform the movement or cannot stay on one leg stance.
Figure 5. A-B. Step Up (frontal visual evaluation, right and left sides separately). Standardized instructions: “First, stand behind the
aerobic step facing forward (towards the videocamera), feet aligned about hip-width apart. Then, step up and down (backwards) on
the step starting with your right leg. Repeat the movement four times. Then, perform the movement starting with your left leg”. A)
Correct performance (0 points): Movement is stable and easy. Alignment of the hip, knee and foot are good (no varus or valgus). There
are not compensating movements. B) Incorrect performance (1 point): Insecurity or helping with hands in the air. Pelvis does not stay
horinzontal. Alignment of the hip or knee or ankle / foot is not good (eg. there is varus or valgus in the knee or hip is tilting in adduction
or the foot is giving in). Failed performance (2 points): The subject cannot perform the movement.
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P.T. Kaukinen et al.: Movement control reliability in knee OA
anonymously, without showing the face, so that the person
could not be identified. Each test was videoed separately
and it took approximately 10 minutes per participant to
perform the test set. Participants wore underwear so that
posture and movements of lumbar spine, pelvis, hips and
lower extremities could be observed.
All participants were without any pain medication for
at least 24 h before the testing visits, and any unfamiliar
sporting activity was prohibited for one week prior the
measurements to avoid delayed onset muscle soreness.
Bedside examination including motor, sensory and deep
tendon refl ex testing to exclude (su bclinical) polyneuropathy
was performed36 at the beginning of the first visit and the
participants with abnormal findings were excluded.
Rating of the test performance
Two experienced physiotherapists, EOH and HAL, blinded
to the medical history and to each other rated the test
performance in random order. Both raters are experienced
physiotherapist with 30 years working experience. They
reviewed the protocol thoroughly with each other and
practised the ratings with videos. One physiotherapist (HAL)
re-rated the test performances after 2 months period blinded
to his earlier rates. The test performance was rated on
3-point scale as correct, incorrect or failed (i.e. subject could
not perform the test). The criteria for correct and incorrect
performance are presented in Figures 1-6.
Statistical analysis
Mean values and standard deviations (SDs) were calculated
for all continuous variables. The number of incorrect or failed
test performances was calculated for each test for index knee
and contralateral knee with the exception of the squat to 90
degrees knee flexion in which only the performance of the
index knee could be evaluated. For the controls the index
knee was randomly selected. The sum (0-6) of incorrect test
performances, named as MC score, was calculated for the
index knee and the contralateral knee in both groups and an
average of incorrect tests was calculated separately for knee
OA subjects and controls. Paired samples t test was used to
compare MC score between the index knee and contralateral
knee in both groups. Because these groups were neither age-
or sex -matched nor equal in size, no comparisons between
the groups were performed.
In the reliability analyses the data from both groups
(subjects with knee OA and controls) were treated as a
whole cohort. For intertester and intratester reliability
of each test, weighted kappa (wK) coefficient with 95%
confidence interval (95%CI) and the percentage of
agreement were calculated for each test. WK coefficients
were interpreted according to Landis and Koch37 (0. 81-
1 excellent agreement, 0.61-0.80 good, 0.41-0.60
moderate, 0.21-0.40 fair and <0.20 poor agreement).
The definition of acceptable reliability was set on wK≥0.4
with lower bound of 95% CI≥0.2. Intraclass correlation
coefficients (ICCs) with 95% confidence interval were
Figure 6. A-B. Step Down (frontal visual evaluation, right and left sides separately). Standardized instructions: “First, stand on the
aerobic step facing forward (towards the videocamera), feet aligned about hip-width apart. Then, step down with your right leg so that
the heel touches the floor first. Then, take a couple of steps forward , turn around and walk behind the aerobic step, step up and repeat the
movemen t starting with your r ight leg four times. Afterwards, per form the movement startin g with your left leg”. A) Correct performance
(0 points): Movement is stable and easy. Alingnment of the hip, knee and foot are good (no varus or valgus). There are not compensating
movements. B) Incorrect performance (1 point): Insecurity or helping with hands in the air. Pelvis does not stay horinzontal. Alignment
of the hip or knee or ankle / foot is not good (eg. there is varus or valgus in the knee or the hip is tilting in adduction or the foot is giving
in). Failed performance (2 points): The subject cannot perform the movement.
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P.T. Kaukinen et al.: Movement control reliability in knee OA
Tabl e 2. Characteristics of study subjects.
Knee OA subjects (n=29) Controls (n=12)
Age (years), mean (SD) 65 (9) 37 (16)
Sex
Female, n (%) 22 (76) 4 (33) (33. 3)
Male, n (%) 7 (24) 8 (67) (66.7)
Body mass index (kg/m2), mean (SD) 29 (5) 27 (2) 27.2 (1.5)
Duration of knee pain (years), mean (SD) 7 (7)
Knee pain, VAS (mm) , mean (SD)
Index knee 34 (26)
Contralateral knee 8 (13)
WOMAC
Pain subscale (mm), mean (SD) 35 (17)
Function subscale (mm), mean (SD) 2 7 (16)
Radiographic grades (Kellgren-Lawrence) of the
index knee, n (%)
14 (14)
214 ( 4 8)
310 (34)
41 (3)
Tabl e 3. Number of incorrect or failed test performances for each test and MC score1.
Index2 Knee Contralateral3 Knee
Tes t Knee OA subjects
n=29
Controls
n=12
Knee OA subjects
n=29
Controls
n=12
Small Squat to 30 Degrees Knee Flexion
Incorrect, n (%) 7 (24) 3 (25 25.0) 8 (28 27.6) 3 (25)
Failed, n (%) 0000
Squat to 90 Degrees Knee Flexion
Incorrect, n (%) 9 (31) 1 (8) na na
Failed, n (%) 0 0 na na
One-Leg Stance
Incorrect, n (%) 10 (35) 3 (25) 11 ( 38 ) 3 (25)
Failed, n (%) 4 (14) 1 (8) 3 (10 ) 1 (8)
Small Squat on One-Leg Stance
Incorrect, n (%) 11 (3 8) 3 (25) 13 (4 5) 5 (42)
Failed, n (%) 14 (4 8) 1 (8) 8 (28) 1 (8)
Step Up
Incorrect, n (%) 11 (3 8) 1 (8) 8 (28) 1 (8)
Failed, n (%) 0000
Step Down
Incorrect, n (%) 18 (62 ) 016 ( 55 ) 3 (25)
Failed, n (%) 0000
MC Score, mean (SD) 2.9 (2) 1.1 (2) 2.6 (2) 1.5 ( 2)
1 MC Score = the sum (0-6) of incorrect test performances.
2 Index Knee = symptomatic (or more symptomatic) knee in the subjects with knee OA and randomly selected knee in the controls.
3 Contralateral Knee = asymptomatic (or less symptomatic) knee in the subjects with knee OA and contralateral knee in the controls
na = not assessable: in the squat to 90 degrees knee flexion test only the performance of the index knee could be evaluated.
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P.T. Kaukinen et al.: Movement control reliability in knee OA
used to assess inter- and intratester reliability of MC
score using two-way mixed effects analysis of variance,
type consistency with single measures. ICC values were
interpreted according to guidelines established by
Shrout and Fleiss38 where values >0.75 indicate excellent
reliability, 0.6-0.75 is good reliability, 0.4-0.59 is fair
reliability, and <0.4 is poor reliability.
Statistical tests were performed two-tailed and at the 5%
significance level. All statistical calculations were performed
using the Statistical Package for the Social Sciences (version
22, SPSS Inc., Chicago, IL, USA).
Results
29 subjects with knee OA with mean age of 65 (SD 9)
years (22 [76%] female) and 12 controls (mean age 37 (16)
years, 33% female) were included. The demographic data
of study subjects are shown in Table 2. The mean duration
of symptoms in knee OA subjects was 7 (SD 7) years and
4 (14%) had Kellgren-Lawrence (K-L) 1, 14 (48%) K-L 2,
10 (34%) K-L 3 and 1 (3%) K-L 4 radiographic OA. Mean
pain in the more symptomatic knee was 34 (26) mm and in
the contralateral knee 8 (13) mm. 16 (55%) of the knee OA
subjects had bilateral symptoms.
The number of incorrect or failed test performances for
each test and MC score for both index knee and contralateral
knee are presented in Table 3. On average, knee OA subjects
performed 2.9 out of 6 tests (SD1.5) incorrectly with their
more symptomatic (index) knee compared to 2.6 (1.6) of
their less symptomatic/ asymptomatic (contralateral) knee
(p=0.103). In the control group, on average, 1.1 (SD 1.6) out
of 6 tests in the index knee and 1.5 (1.7) in the contralateral
knee were performed incorrectly ( p = 0.1 875 ).
Intertester reliability
The weighted Kappa (wK) values with 95% CI for
intertester reliability and the percentage of agreement of
each movement control test are shown in Table 4. One-leg
standing test (wK for the index knee 0.60, 95% CI 0.42-0.79
and for the contralateral knee 0.63, 0.44-0.82) showed
good and one-leg squatting test moderate (wK for the index
knee 0.52, 95% CI 0.34-0.69 and for the contralateral
knee 0.43, 0.23-0.62) reliability in both sides and step
down test showed excellent reliability in the index i.e. more
sym ptomatic knee (wK 0.85, 95% CI 0.69-1.00) but only
moderate reliability in the contralateral knee (wK 0.55, 95%
CI 0.30-0.80). Other tests showed fair or poor intertester
reliability (wK range 0.09-0.41).
Table 4. Intertester and intratester reliability of the movement control tests and the percentage (%) of agreement.
Intertester Reliability Intratester Reliability
Tes t Weighted Kappa
(95% CI1)% Agreement Weighted Kappa
(95% CI1)% Agreement
Small Squat to 30 Degrees Knee Flexion
Index Knee 0.38 (0.06-0.71) 78 0.28 (-0.05-0.62) 78
Contralateral Knee 0.30 (-0.02-0.62) 78 0.35 (0.05-0.66) 81
Squat to 90 Degrees Knee Flexion
Index Knee 0.09 (-0.09-0.28) 76 0.50 (0.17-0.82) 85
Contralateral Knee na2na2
One-Leg Stance
Index Knee 0.60 (0.42-0.79) 85 0.65 (0.43-0.86) 78
Contralateral Knee 0.63 (0.44-0.82) 85 0.71 (0.50- 0.91) 81
Small Squat on One-Leg Stance
Index Knee 0.52 (0.34-0.69) 76 0.73 (0.56-0.90) 88
Contralateral Knee 0.43 (0.23-0.62) 73 0.66 (0.46-0.85) 88
Step Up
Index Knee 0.41 (0.12-0.71) 81 0.36 (0.05-0.67) 78
Contralateral Knee 0.38 (0.03-0.73) 83 0.38 (0.03-0.73) 81
Step Down
Index Knee 0.85 (0.69-1.00) 93 0.80 (0.62-0.99) 90
Contralateral Knee 0.55 (0.30-0.80) 78 0.51 (0.24-0.77) 76
1 CI= confidence interval
2 na= not assessable
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P.T. Kaukinen et al.: Movement control reliability in knee OA
Intraclass correlation coefficient (ICC) for intertester
reliability of the sum score of the tests was 0.71 (95% CI
0.51-0.83) for the index knee and 0.64 (0.42-0.79) for the
contralateral knee showing good reliability.
Intratester reliability
The weighted Kappa (wK) values with 95% CI for
intratester reliability and the percentage of agreement of
each movement control test are shown in Table 4. One-leg
standing test (wK for the index knee 0.65, 95% CI 0.43-
0.86 and for the contralateral knee 0.71, 0.50-0.91) showed
moderate and one-leg squatting test good (wK for the index
knee 0.73, 95% CI 0.56-0.90 and for the contralateral
knee 0.66, 0.46-0.85) reliability in both sides and step
down-test showed excellent reliability in the index i.e. more
symptomatic knee (wK 0.80, 95% CI 0.62-0.99) but only
moderate reliability in the contralateral knee (wK 0.51, 95%
CI 0.24-0.77). Other tests showed fair or poor intratester
reliability (wK range 0.28-0.50).
ICC for intratester reliability of the sum score of the tests
was 0.68 (0.47-0.82) for the index knee and 0.71 (0.51-
0.83) for the contralateral knee showing good reliability.
Discussion
Our study evaluated the intertester and intratester
reliability of movement control impairment (MCI) tests of
lower extremities in subjects with knee OA and controls
without either knee pain or previous diagnosis of OA. Three
out of six tests (one-leg stance, one-leg squat 30 degrees,
step down test) showed moderate to excellent inter- and
intratester reliability, and both the intertester and intratester
reliability for sum score of the six tests (MC score) was good.
To our knowledge this is the first study to assess the
reliability of MC tests in knee OA. However, similarities can be
found in earlier studies evaluating the reliability of movement
control tests in lower extremities, hip or back in healthy
subjects39-4 3, in hip OA24 and in low back pain22,44 .
Asprion et al.24 assessed the reliability of movement
control tests in the subjects with hip OA in almost identical
setting than ours (movement control test battery consisting
of five tests: small squat 30 degrees, squat to 90 degrees,
one-leg stance, small single leg squat and step up tests) and
found acceptable intertester (weighted kappa, wK 0.52-
0.71) and intratester (wK for experienced rater 0.56-0.87
and for less experienced rater 0.35-0.61, respectively)
Tabl e 5. Quality appraisal of diagnostic reliability (QAREL) checklist48.
Question Answer Explanation
Was the test evaluated in a sample of subjects who were
representative of those to whom the authors intended the
results to be applied?
Yes
The subjects with knee OA represented the subjects to whom the
results are intended to be applied. Both primary and secondary
care patients were included with different stages of the disease. The
control group, however, was not age- and gender-matched.
Was the test per formed by the raters who were
representative of those to whom the authors intended the
results to be applied?
Yes
Were raters blinded to the findings of other raters during
the study? Yes
Were raters blinded to their own prior findings of the test
under evaluation? Yes
Were raters blinded to the results of the accepted
reference standard or disease status for the target
disorder (or variable) being evaluated?
Yes Raters were blinded to the disease status of the subjects.
Were raters blinded to clinical information that was not
intended to be provided as part of the testing procedure
or study design?
Yes
Were raters blinded to additional cues (e.g. history,
imaging, blood tests) that were not part of the test? Unclear It might be possible to conclude from the videotapes whether the
subject is having knee OA for example due to deformity of the knee.
Was the order of examination varied Yes Randomized
Was the stability (or theoretical stability of variable
being measured taken into account when determining
the suitability of the time-inter val between repeated
measures?
Yes
In this study the test-retest (intratester reliabilty) was evaluated
from one videoed test performance in two separate sessions. Thus,
potential variablity over time (for example due to present pain or as
a consequence of learning were eliminated.
Was the test applied correctly and interpreted
appropriately? Yes
The tests are described in detail including rationale, procedure
and interpretation. Interpretation of the tests were discussed and
agreed by the raters.
Was appropriate statistical measures of agreement used? Yes
206http://www.ismni.org
P.T. Kaukinen et al.: Movement control reliability in knee OA
reliability. They suggested the use of squat to 90 degrees,
one-leg stance, small single leg squat and step up tests in
evaluating subjects with hip OA24 . Better reliability in the
90 degrees squat test and step up test in their study may
reflect the differences in our study populations (hip OA
versus knee OA) and better sensibility of these tests to reveal
movement control impairment in the subjects with hip OA.
It can be hypothesised that by hip OA patients the control
and differentiation between hip and low back is much more
critical than by patients with knee problems.
In low back pain, intratester reliability of movement
control tests has been varied from moderate to very good
and intertester reliability from poor to very good23. One-leg
stance test has shown constantly very good agreement22-44.
Despite the similarity of the test performance in the one-
leg stance test, the differences between the use of test are
obvious: in our study the alignment and movement of lower
extremity, i.e. the presence of excessive medial rotation of
the involved femur, knee hyperextension or excessive ankle
pronation were assessed, in addition to pelvic tilt44. The
rotation44 or lateral shift of the pelvis22 was not assessed in
our study like it has been done by patients with low back pain.
In knee OA the one-leg stance test has been used as a
measure of postural balance with high repeatability and
validity45,46 with findings of postural deficits in the knee OA
subjects compared to healthy age-matched controls47,4 8 . To
our knowledge, the control of movement in one-leg standing
position has not been investigated in this population. Even if
a minority of our study subjects failed one-leg stance test
(i.e. was not able to stand in one-leg for 10 seconds), it is,
important to notice that also poor balance may have affected
the subjects’ performance and might be an independent
contributor to the subjects’ pain problem17.
The reliability of one-leg squat test has been evaluated
in healthy subjects with good-to-excellent intertester
reliability39-41,43 and fair-to-excellent intratester
reliability40,41,43. Good intertester and intratester reliability of
one-leg squat test was also reported by Asprion et al.24 in the
hip OA subjects. The evaluation criteria for test performance
have been variable with the criteria of Asprion et al.24,
Poulsen et al.41 and Crossley et al.40 being closest to ours.
It is worth to note that a substantial part (48% compared
to 38% with incorrect performance, respectively) of knee
OA subjects failed (i.e. were unable to perform) the one-
leg squat test in our study. This may be due to aggravating
pain during the activity forcing the subjects to discontinue
their performance. In the future, assessment of the impact
of movement impairment modifications on the pain and
subject’s performance would show whether the activity
might be influenced with such a manner or if the pain severity
is too high for this kind of activity for at least a subgroup
of knee OA patients17. Movement control impairment is not
characterised with intensive pain and extensive limitations17.
Based on our results, in evaluating MC in subjects with knee
OA, the high-level activities such as one-leg squat might be
most useful in subjects with earlier stage of the disease with
less disabling pain.
With the remaining three tests (small squat to 30 degrees,
squat to 90 degrees knee flexion and step up tests) with poor
reliability, the result just shows the complexity of the clinical
evaluation of the MC23. Majority of the subjects with knee
OA performed these tests correctly and one explanation of
poor reliability of the remaining tests might be that they were
too easy to perform and thus incapable to reveal movement
control impaiment17.
Our study has both strengths and limitations. When
observed through the QAREL tool49 (Table 5), the study
protocol was well designed and thus, decreases the risk of
bias. The subjects with knee OA represented the subjects to
whom the results are intended to be applied. Both primary
and secondary care patients were included with different
stages of the disease. The control group was not age- and
sex -matched, but we considered important to include in
to the study sample subjects who would perform the tests
well in order to increase variability of the results and thus
avoid a possible bias of the results of too many incorrect or
failed test performance31. However, as a consequence, even
if there seemed to be a difference between the groups in the
average number of incorrect tests (the subjects with knee OA
performed on average 2.9 tests incorrectly with their index
knee compared to 1.1 incorrect tests in healthy volunteers),
we were not able to assess the discriminative validity of MC
tests reliably because the groups were neither age- and
gender-matched nor equal in size.
Also, it is worth to mention as a limitation that intratester
reliability could be affected by a systematic error as the
analysis was based on re-ratings by only one, not both, raters.
In our study the intratester reliability was evaluated
from one videoed test performance in two separate
sessions and thus the effect of pain variability and learning
on variability of the results was eliminated. However, in the
future studies it is important to investigate the test-retest
reliability of the tests through separate testing sessions
because in clinical practice such tests are commonly used
for follow-up evaluations42.
Conclusions
One-leg stance test, one-leg squat 30 degrees and step
down -test are reliable in the subjects with knee OA and
healthy volunteers. The three further tests showed only
poor reliability. Use of the three reliable tests in the subjects
with knee OA may increase our clinical knowledge of the
mechanisms of pain and help us to create more efficient,
patient-specific treatments. Further research is needed to
evaluate the discriminative validity of these tests.
Acknowledgements
We thank Tuomas Selander, M.Sc, for his advice for the statistical
analyses. Furthermore, we would like to thank all participants of the
study and the person in the photographs. She gave her written consent
allowing their use for publication.
207http://www.ismni.org
P.T. Kaukinen et al.: Movement control reliability in knee OA
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