Efficacy of a biomechanically-based yoga exercise program in knee osteoarthritis: A randomized controlled trial
Efficacy of a biomechanically-based yoga exercise program in knee osteoarthritis: A randomized controlled trial
Alexander B. Kuntz 0 1
Jaclyn N. Chopp-Hurley 0
Elora C. Brenneman 0 1
Sarah Karampatos 0
Emily G. Wiebenga 0
Jonathan D. Adachi 0
Michael D. Noseworthy 0
Monica R. Maly 0 1
Andrea Martinuzzi, IRCCS E. Medea, ITALY
0 Community in Southwestern Ontario , Canada
1 Department of Kinesiology, McMaster University , Hamilton, Ontario , Canada , 2 School of Rehabilitation Sciences, McMaster University , Hamilton, Ontario , Canada , 3 Department of Medicine, McMaster University , Hamilton, Ontario , Canada , 4 Department of Electrical and Computer Engineering, McMaster University , Hamilton, Ontario , Canada , 5 Department of Kinesiology, University of Waterloo , Waterloo, Ontario , Canada
Funding: Project funding was received through a
Canadian Institutes for Health Research (CIHR)
Bridge Grant #137147 (MRM). Funding for certain
equipment used in this research was received
through the Canada Foundation for Innovation and
the Ontario Research Fund. Alexander Kuntz was
supported by the Joint Motion Program (A CIHR
training initiative) and the Ontario Graduate
A convenience sample of 31 women with symptomatic knee osteoarthritis was recruited
through rheumatology, orthopaedic and physiotherapy clinics, newspapers and
word-ofParticipants were stratified by disease severity and randomly allocated to one of three
12week, supervised interventions. YE included biomechanically-based yoga exercises; TE
included traditional leg strengthening on machines; and NE included meditation with no
exercise. Participants were asked to attend three 1-hour group classes/sessions each
Scholarship. Jaclyn Chopp-Hurley was supported
through the Michael G. DeGroote Fellowship Award
in Clinical Research at McMaster University and a
CIHR fellowship award. Elora Brenneman was
supported by an Ontario Graduate Scholarship.
Monica Maly was supported by a CIHR New
Competing interests: The authors have declared
that no competing interests exist.
Primary outcomes were pain, self-reported physical function and mobility performance.
Secondary outcomes were knee strength, depression, and health-related quality of life. All were
assessed by a blinded assessor at baseline and immediately following the intervention.
The YE group demonstrated greater improvements in KOOS pain (mean difference of 22.9
[95% CI, 6.9 to 38.8; p = 0.003]), intermittent pain (mean difference of -19.6 [95% CI, -34.8
to -4.4; p = 0.009]) and self-reported physical function (mean difference of 17.2 [95% CI, 5.2
to 29.2; p = 0.003]) compared to NE. Improvements in these outcomes were similar between
YE and TE. However, TE demonstrated a greater improvement in knee flexor strength
compared to YE (mean difference of 0.1 [95% CI, 0.1 to 0.2]. Improvements from baseline to
follow-up were present in quality of life score for YE and knee flexor strength for TE, while both
also demonstrated improvements in mobility. No improvement in any outcome was present
The biomechanically-based yoga exercise program produced clinically meaningful
improvements in pain, self-reported physical function and mobility in women with clinical knee OA
compared to no exercise. While not statistically significant, improvements in these
outcomes were larger than those elicited from the traditional exercise-based program. Though
this may suggest that the yoga program may be more efficacious for knee OA, future
research studying a larger sample is required.
Knee osteoarthritis (OA) is associated with pain, mobility limitations, and a variety of
comorbidities such as cardiovascular, gastrointestinal, and metabolic diseases, as well as depression
]. Conservative treatment options are necessary to make meaningful use of time spent using
analgesics and, for some, the multi-year gap between diagnosis and joint replacement. Exercise
provides equivalent pain relief to medication while also improving physical function,
comorbidities, and quality of life [2±4]. However, some features of common exercises can exacerbate
symptoms and contribute to disease progression. For example, exposure to elevated
magnitudes of the knee adduction moment (KAM), a mechanical variable reflecting the ratio of
medial to total knee loading, predicts disease progression [5±8], with repetitive exposure
linked to pain severity in OA [
]. Therefore, it is critical to ensure that exercise prescriptions
for knee OA minimize exposure to KAM.
Yoga may be an ideal exercise option for knee OA. If the correct postures are selected,
exposure to end-range joint positions and large KAM can be reduced [
]. Yoga also involves
cultivating ªmindfulnessº; that is, paying deliberate attention in a non-judgmental manner to
one's experience of the present moment . Mindfulness practice can ameliorate pain in
chronic conditions like arthritis [
]. This is an important paradigm for interventions
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aimed to address the symptoms of OA that are both physiological and psychological [
Although a lack of high quality evidence exists, existing literature suggests yoga is a promising
and safe treatment for OA [
]. In a 12-week cohort study of women with knee OA, we
previously demonstrated that yoga reduced pain, increased knee muscle strength, and improved
physical function and mobility performance . It remains unclear how the improvements in
symptoms, mobility and physical capacity compare between this novel yoga exercise program
based on biomechanical principles [
] versus a traditional exercise program prescribed for OA.
The purpose of this study was to compare the effectiveness of a biomechanically-based yoga
exercise intervention to traditional exercises for knee OA, and an attention-equivalent no
exercise control group in women with clinical knee OA. The primary outcomes were pain,
selfreported physical function and mobility performance. We also investigated knee muscle
strength, depression, and health-related quality of life. It was hypothesized that the yoga group
would experience greater improvements in all outcomes compared to the no exercise group;
and equal or greater improvements compared to traditional exercise group.
Materials and methods
Setting and participants
This study was a single-blind, three-arm, parallel, randomized controlled trial.
This trial (NCT02370667) was conducted at McMaster University in Hamilton, ON, Canada
and was approved by the Hamilton Integrated Research Ethics Board (#15±021) where all
participants provided written informed consent.
A sample size calculation for an analysis of covariance (ANCOVA) designed to detect
significant differences in three primary outcomes between three groups with one covariate (baseline
values) was performed. A systematic review of yoga as a therapeutic intervention for adults with
chronic pain concluded yoga is capable of reducing pain by a standard mean difference of -0.74
(95% CI, -0.97 to -0.52; P < 0.0001) [
]. Given this moderate effect size, high correlation
between outcomes, a 5% chance of type one error (two-sided) and 15% attrition, a sample of 60
participants was recommended to yield 80% power to detect between group differences.
Participants were recruited through rheumatology, orthopaedic, and physical therapy
clinics, as well as by word-of-mouth and newspaper advertisements in the Hamilton, Ontario,
Canada region between April and June 2015. The sample included ambulatory,
communitydwelling women, 50 years of age or over, who met the diagnostic criteria for clinical knee OA
according to the American College of Rheumatology [
]. Clinical OA diagnostic criteria were
chosen given that radiographic disease severity does not appear to influence the effectiveness
of exercise [
]. Exclusion criteria consisted of other forms of arthritis, history of osteoporotic
fracture, patellofemoral pain, non-arthritic knee disease, knee surgery, unstable heart
condition, neurological conditions, physician-advised physical activity restrictions, skin allergy to
medical tape, lower limb trauma in past three months, ipsilateral hip or ankle conditions,
undergoing cancer treatment, and pregnancy.
Randomization and interventions
Participants were randomized to one of the three study interventions after stratification for
disease severity. Disease severity was determined using the Lower Extremity Functional Scale
] a 20-item measure addressing lower extremity physical function limitations
associated with musculoskeletal conditions affecting the lower extremity. This tool is scored out
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of 80, where higher scores indicate better function. It was designed such that it is easy to
administer and score and applicable to a wide range of people with lower limb conditions. Mild
limitation was regarded as LEFS scores between 51 and 65, and those between 30 and 50 were
moderate . After stratification, randomization was performed using custom Matlab1
software, with a block size of n = 6 and 1:1:1 allocation ratio. The intervention arms included a yoga
exercise (YE) experimental group, a traditional exercise (TE) active treatment comparison
group, and a no exercise (NE) attention-equivalent control group. Participants received group
allocation information in an opaque envelope. This process was completed by an investigator
who was not involved in data collection. All data collection was led by an investigator who was
blind to group allocation and uninvolved in the interventions. Participants and exercise
instructors were blinded to the study hypothesis. All three interventions were 12-weeks in duration.
For each of the three interventions, participants were asked to attend three of four available
one-hour classes/sessions each week. The classes/sessions were supervised. The interventions
took place between June and September 2015 in Hamilton, Ontario, Canada.
The group YE intervention was led by a certified, trained yoga instructor. YE consisted of
alignment-based postures that activate the lower limb musculature while maintaining a low
]. The selected weight-bearing, static poses were performed barefoot and included
squats and lunges with varying foot, trunk, and arm positioning. Careful attention was given
to ideal alignment of the leg throughout the exercises. The classes began with a body-awareness
exercise performed in supine followed by the strengthening postures and concluded with a
closing deliberate relaxation exercise performed in supine. Exercise difficulty was progressively
increased over the 12-week intervention period.
The TE intervention reflected the current gold standard of strengthening exercise for knee
]. The program emphasized knee strengthening but also involved an aerobic warm-up,
balance exercises, and stretching. TE was designed and supervised by kinesiologists and
physical therapists and took place at a physical activity center. The sessions involved a ten-minute
warm-up performed on a treadmill or cycle ergometer. Then, lower extremity strengthening
was performed on pneumatically-resisted exercise machines (HUR USA, Inc., Northbrook, IL,
USA). Exercises included all major muscle groups of the lower extremity. The quadriceps were
targeted at every session. Participants also completed balancing activities and static stretching.
There was a progressive increase in the number of sets and resistance during strengthening
exercises over the course of the intervention.
In both YE and TE, participants were asked to exercise at an intensity of seven out of ten on
the Borg Perceived Exertion Scale [
]. Participants were also asked to rate their knee pain on
a visual analog scale [
] prior to each session and ensure that pain levels were not exacerbated
by more than two points. In the event that pain increased more than two points during a
session, participants were asked to notify the instructor for an appropriate modification [
The NE intervention consisted of group-based, guided meditative relaxation classes led by a
certified yoga-instructor. These sessions included non-physically active somatic awareness
exercises including breath and body-scan meditation practices performed in passive postures
fully supported by the use of yoga props.
Strategies to enhance participant adherence included a gift bag after the initial data
collection visit, rewards for best attendance halfway through intervention, and a $50 stipend upon
study completion. Session attendance and program adherence was monitored.
Outcomes and follow-up
All outcomes were measured before and immediately after the 12-week intervention and led
by the same blinded assessor. The primary outcomes were pain, self-reported physical function
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and mobility performance. Multiple primary outcomes were selected to ensure that both
selfreported and performance-based measurements were included, since these outcomes reflect
unique elements of OA disease [27±29]. Further, mobility performance was assessed using the
set of tools that is recommended for interventional studies of knee OA [
outcomes included muscle strength, symptoms of depression, and health-related quality of life.
Because OA affects multiple elements of health [
]; and the mechanisms by which yoga
improves health appears multifactorial [
], these broader constructs relevant to health and
well-being were explored. Adverse events were tracked by having participants complete a
report at follow-up that asked whether they experienced an event that may have affected their
quality of life or function since the last visit. This report was standard across participants.
Primary outcomes. Pain was assessed using the pain subscale of the Knee Injury and
Osteoarthritis Outcome Score (KOOS) and the Measure of Intermittent and Constant
Osteoarthritis Pain (ICOAP). The KOOS pain subscale yields a score of pain intensity during a
variety of movements and activities. It is a nine-item tool answered on a five-point Likert scale.
Scores are normalized out of 100; lower scores indicate more extreme and troublesome
symptoms. In contrast to the KOOS, the ICOAP provides information on pain intensity and
frequency, and the consequent effects on aspects of life independent of the effects of pain on
physical function. The ICOAP is an 11-item questionnaire where higher scores are indicative
of more severe pain. The tool was designed to distinguish the OA pain experience into
constant pain and intermittent pain, and yields scores for the most troublesome joint and the
resulting impact on mood, sleep, and quality of life. Both the KOOS and ICOAP produce valid
and reliable data in adults with knee OA [
Self-reported physical function was assessed using the LEFS, as well as the function in
activities of daily living (ADL) and sport and recreation (SR) subscales of the KOOS. The LEFS has
20 items that assess difficulty during mobility tasks. This tool avoids ceiling effects in high
functioning samples and has superior sensitivity and discriminant validity than KOOS
]. Low LEFS scores represent poor mobility [
]. The ADL and SR subscales are
17-item and 5-item tools respectively; where higher scores indicate better function.
Mobility performance measures included those recommended by the Osteoarthritis
Research Society International: the six-minute walk (SMWT), 40-meter walk (40mW),
30-second chair stand (30sCS), timed up and go (TUG), and stair ascent (SA) tests [
]. In the
SMWT test, participants were instructed to walk as far as possible in six-minutes; the distance
travelled was recorded. Time spent walking the initial 40 meters of the SMWT was used as
40mW score. The number of times participants were able to rise from and return to a chair in
30 seconds was the 30sCS score. The TUG test involved measuring the duration of time
required for participants to rise from a chair, walk three meters, and return to their seat. All of
these mobility performance measures produce valid and reliable data in individuals with knee
OA [35±38]. Lastly, time taken to ascend a 9-step staircase as quickly as possible, with or
without the use of a handrail, was recorded for the SA test. This stair climbing assessment produced
reliable data (ICC 0.72±0.88, SEM <0.4s) in 29 healthy adults in our laboratory.
Secondary outcomes. Muscle strength was represented by peak torque of the knee
extensor and flexor muscle groups of participants' most symptomatic knee during maximal
voluntary efforts. Participants were positioned on a dynamometer (Biodex System 2, Biodex
Medical Systems, Shirley, NY, USA) with the knee joint center aligned with the device axis of
rotation and in 65Ê of flexion relative to full extension. Torso, pelvis, thigh, and lower leg
restraints were used to minimize the contribution of other muscle groups. Apparatus settings
were recorded for each participant at baseline and replicated during follow-up for consistency.
Participants completed five maximal voluntary isometric muscle actions following a
submaximal, isotonic warm-up and familiarization. Each effort lasted five seconds, with five seconds of
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rest between bouts. Participants were provided with verbal encouragement and visual feedback
to maximize voluntary effort. The peak torque value obtained during these five efforts was
expressed relative to body mass (Nm/kg).
Symptoms of depression were evaluated using the Center for Epidemiological Studies
Depression Scale (CESD). The CESD is a 20-item tool inquiring about affect (mood, guilt,
worthlessness, helplessness, appetite, and sleep) that produces valid and reliable data in the
general population and individuals with rheumatoid arthritis [
]. Quality of life was
assessed using the four-item knee related quality of life (QoL) subscale of the KOOS.
Descriptive statistics were calculated. A one-way ANOVA was used to detect whether
differences in age, BMI and LEFS score existed between groups baseline. An ANCOVA comparing
mean change scores across the intervention (follow-up minus baseline), with baseline data
used as covariates in the models were used to detect between-group differences for each
outcome. Sidak adjustments were performed to account for multiple comparisons between
groups; alpha values of 0.05 were used. Assumptions of ANCOVA were tested and met [
Data distribution was assessed visually and using Shapiro-Wilk tests; homoscedasticity was
assessed using Levene's test for equality of error variance; independence of covariate and
treatment effect was assessed using a one-way analysis of variance (ANOVA); and homogeneity of
regression slopes of covariates versus dependent variables was assessed visually and by testing
group allocation by baseline score interactions in an ANOVA. Paired (two-tailed) t-tests
between pre and post intervention group means were also calculated to detect within-group
differences. A Bonferroni correction was used to adjust for multiple within-group
comparisons; an alpha value of 0.0167 was used. Statistical analyses were conducted using SPSS v. 23
(IBM, IL, USA). Additionally, to evaluate clinical significance, outcomes were interpreted
relative to the minimal clinically important differences (MCID) and patient acceptable symptoms
states (PASS). The MCID represents the smallest increment of change that a patient would
identify as important. The PASS values are those in which scores equal or above are deemed
ªunacceptableº to live with by individuals with OA [
Participant recruitment, retention, and adherence
Participant recruitment began in April 2015 and follow-up data collection was completed by
September 2015. A total of 59 individuals were screened for eligibility; of these, some did not
meet the inclusion criteria (n = 19), or declined to participate (n = 9). Thirty-one individuals
were stratified by LEFS score and randomly allocated to either YE (n = 10), TE (n = 11), or NE
(n = 10) (Table 1). One participant in TE completed only two training sessions and was lost to
follow-up; therefore data from 10 participants in this group were available for per-protocol
analysis. A CONSORT diagram is illustrated in Fig 1. Mean ± standard deviation session attendance
was 3.0±0.75, 2.7±0.52 and 2.7±0.62 sessions per week for YE, TE, and NE, respectively. One
participant in TE was unable to complete the intervention due to an unrelated health diagnosis;
nonetheless, follow-up data was obtained and included in analysis. There were no significant
differences in age (p = 0.17), BMI (p = 0.25), or LEFS scores (p = 0.94) between groups at baseline.
Adverse events and co-intervention
There were no adverse events related to any of the interventions. There was one case of
cointervention. This participant (TE) received one corticosteroid and two hyaluronic acid
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Co-morbidities include self-reported: heart disease, high blood pressure, lung disease, diabetes, ulcer or stomach
disease, kidney disease, liver disease, anemia or other blood disease, cancer, depression, osteoarthritis/degenerative
disease, back pain, rheumatoid arthritis or other conditions.
injections in the right knee on unknown dates throughout the 12-week intervention. Data from
this participant were included in analysis given this series of injections began prior to study.
Significant differences in intervention-induced improvements between the three groups were
present for certain primary and secondary outcomes (Table 2). YE demonstrated a greater
improvement than NE in both KOOS pain (Table 2; Fig 2) and intermittent pain (Table 2),
while differences between YE±TE, and TE±NE were not significant (Table 2; Fig 2). There
were no differences in the change of constant pain between the three groups (Table 2).
Both groups performing exercise (YE and TE) demonstrated greater improvements in
selfreported physical function as measured by the LEFS while there were no significant differences
between the exercise conditions (Table 2; Fig 3). YE demonstrated greater improvements in
KOOS ADL scores compared to NE (Table 2; Fig 4), while differences between YE±TE and
TE±NE were not significant (Table 2; Fig 4). TE reported greater improvements in KOOS SR
scores compared to NE (Table 2; Fig 4). The differences between YE±TE and YE±NE were not
significant (Table 2, Fig 4). One participant in the TE group was removed from analyses of
mobility performance measures as their data existed beyond three standard deviations from
the group mean. There were no significant between-group differences in mean changes for
any of the mobility performance measures (Table 2).
There was a greater increase in knee flexor strength in TE relative to YE (Table 2). There
were no significant differences between groups in mean changes of KOOS QoL scores, CESD
scores, or knee extensor strength (Table 2).
Improvements from baseline to follow-up were present for primary and tertiary outcomes in
the YE and TE exercise groups (Table 3). There was an improvement in KOOS pain (Fig 2;
Table 3), intermittent pain and constant pain in the YE group (Table 3). An improvement in
intermittent pain was also demonstrated in the TE group (Table 3).
Improvements in the LEFS, KOOS ADL and SR scores, as well as certain mobility
performance measures (6MWT, 30sCS, SA) were present in the YE group (Table 3).
Improvements in all mobility measures with the exception of the TUG were present in the TE group
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With respect to secondary outcomes, YE demonstrated an increase in KOOS QoL, while
TE demonstrated an increase in knee flexor strength (Table 3). No other within-group
differences were present in tertiary outcomes.
Fig 1. Consolidated standards of reporting trials (CONSORT) diagram of participant flow throughout recruitment, allocation, data collection and analysis.
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Mean difference (YE minus NE) P value
Mean difference (YE minus TE) P value
Mean difference (TE minus NE) P value
A Sidak adjustment for multiple comparisons was used. Significant differences are denoted with an asterisk .
YE = Yoga Exercise; TE = Traditional Exercise; NE = No Exercise; KOOS = Knee Osteoarthritis Outcome Score; ADL = activities of daily living; SR = sport and
recreation; QoL = quality of life
(/100), n = 5; CESD, n = 1).
Note: due to baseline values of zero, percent difference could not be calculated for certain participants and measures (KOOS Function in SR, n = 2; Constant Pain
9 / 18
Fig 2. Mean ± standard error change (baseline minus follow-up values) in pain scores of the Knee Osteoarthritis
Outcome Score relative to the minimal clinically important difference (MCID) and moderate improvement
values. Significant between-group differences are denoted with and within-group change with .
No significant within-group differences from baseline to follow-up were present for any of
the primary or secondary outcomes in NE (Table 3).
This study featured a direct comparison of a biomechanically-designed yoga program with the
current gold standard of exercise, and a no exercise attention equivalent control in women
Fig 3. Self-reported physical function measured using the Lower Extremity Functional Scale. Data are presented as
mean ± standard error change (follow-up minus baseline values) in scores relative to the minimal clinically important
difference (MCID) values. Significant between-group differences are denoted with and within-group change with .
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Fig 4. Self-reported physical function measured using the Knee Osteoarthritis Outcome Score. Data are presented
as mean ± standard error change (follow-up minus baseline values) in scores relative to the minimal clinically
important difference (MCID) values. Significant between-group differences are denoted with and within-group
change with .
with clinical knee OA. Relative to the NE control group, YE experienced greater improvements
in pain and self-reported physical function. Improvements in such outcomes were similar
between the YE and TE groups. These findings are consistent with the study hypothesis. This
yoga program appears to be an efficacious exercise option that is comparable, and in some
aspects, potentially superior to traditional exercise for alleviating the physically debilitating
symptoms of knee OA in women.
Strengths and limitations
An important feature was the randomized control trial design including an experimental
group, an active treatment comparison group, and an attention-equivalent control group.
However, based on a-priori power calculations this study was underpowered. We aimed to
recruit 60 individuals; however of the 59 individuals we screened for participation, only 31 met
the eligibility criteria and agreed to participate. We did not extend our recruitment period to
boost our sample size to ensure that the group interventions began in a timely manner from
the time of enrolment. Any further delay in commencing the intervention may have resulted
in participant drop-out. As a result of this limited sample, post-hoc analyses revealed observed
power values for the primary outcome measures between 0.32 and 0.81, with all but one over
0.79. We acknowledge this small sample is a key limitation. In future work, we aim to conduct
a larger, multi-site trial to boost our sample size. However, despite this limited sample,
important improvements in pain and physical function were elicited, demonstrating the importance
of exercise for older adults with knee OA. Another limitation is the use of multiple outcome
measures. Knee OA produces multiple sequelae for the person with disease. To capture the
breadth of disease impact as recommended in OA [27±30], we measured pain, self-reported
physical function and mobility performance as primary outcomes. While these measurements
provide insight on the breadth of impact of the interventions, the key focus to improve patient
care should be on pain. As such, pain was used to estimate sample size. Also, due to this small
sample size, we were unable to analyze sub-groups (such as those stratified by age, BMI or
disease severity), and therefore unable to speculate whether the interventions had a greater effect
in some individuals compared to others. These sub-analyzes would be important to consider
in future work. As well, analyses of cartilage morphology, inflammatory markers and
biomechanical analyses were removed because several participants did not consent to and/or
complete these measurements at baseline and follow-up; and cardiovascular fitness and
muscle/fat volume were not measured due to inadequate funding. Further, it is important to
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Significant differences compared using 2-tailed paired t-tests are denoted with an asterisk . A Bonferroni corrected alpha value of 0.017 was used to adjust for multiple
comparisons. KOOS = Knee Osteoarthritis Outcome Score; ADL = activities of daily living; SR = sport and recreation; QoL = quality of life; greater values on KOOS
represent less troublesome scores (including Pain subscale)
consider that while exercises included in the YE intervention were those that imposed a
negligible KAM, knee joint loading incurred during the exercises included in the TE program were
Clinical relevance of findings
The clinical relevance of the measured outcomes was interpreted using MCID and PASS
values. The MCID of LEFS is 5 points [
] and the MCID for KOOS scores is a change of 8 to 10
]. In this sample, clinically important improvements in LEFS scores of 10.6 and 7.6, as
well as KOOS pain scores of 21.5 and 8.3, were observed in the YE and TE groups, respectively.
A change of 15 points is indicative of ªmoderate improvementº for KOOS pain [
]. In the YE
group, all 10 participants demonstrated improvements in pain scores above the MCID with 8/
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10 demonstrating a moderate improvement ( 15 points). For TE and NE groups, 5/10 and 3/
10 participants had improvements above the MCID. For the LEFS, 6/10, 5/10 and 2/10
participants had clinically important improvements in the YE, TE and NE groups, respectively.
Improvements in intermittent and constant pain subscales of the ICOAP met the MCID in
YE only [
]. The PASS values for the ICOAP are reportedly 40 for intermittent pain and 20
for constant pain [
]. At baseline, all three groups reported intermittent and constant pain
scores greater than PASS values; indicating unacceptable levels of pain. At follow-up,
intermittent pain scores were less than the PASS value in the YE and TE groups, while for constant pain,
only the YE group attained a mean score less than the PASS value. Examining individual scores,
in the YE group 7/10 and 8/10 participants had constant and intermittent ICOAP scores that
were less than the PASS value, indicating pain intensity was likely considered acceptable to the
participant. This compared to 4/10 and 8/10 for the TE group and 4/10 and 5/10 for the NE
group for constant and intermittent scores, respectively. Regarding quality of life, YE and TE
met the MCID in the KOOS ADL scores (Fig 4). For KOOS SR scores, clinically important
improvements of 21.3 and 29.2 were observed in the YE and TE groups, respectively (Fig 4)
]. A non-clinically relevant decrease of 2.7 was observed in the NE group [
There are no established MCID values for mobility performance measures after an exercise
intervention among those with knee OA. In OA of the hip, an increase of 2 to 3 repetitions in
the 30sCS test and a decrease of 0.8 to 1.4 seconds in the TUG test have been considered
clinically important [
]. In the current study, the YE and TE groups performed an additional 3.4
and 2.5 repetitions in the 30sCS test, respectively; and decreased TUG times by 1.4 and 0.3
Conceptually, the MCID represents improvement associated with ªfeeling better;º whereas
the PASS is designed to reflect partial symptomatic remission, relating to ªfeeling goodº [
From a clinical standpoint, the YE group appeared to achieve more meaningful improvements
in pain and self-reported physical function compared to the TE and NE groups. However,
despite demonstrating larger improvements in pain and function in the YE group compared to
the TE group, there were no significant differences between the interventions. This finding may
seem surprising because the YE group received an intervention combining mindfulness and
biomechanical exercise, compared to TE which received exercise alone. However, because that
the intervention focussing on mindfulness alone (NE group) yielded no meaningful benefits, it
seems reasonable that the mindfulness element of YE yielded no benefit above that of physical
exercise. The absence of significant differences between groups may also be attributed to the
small sample size in each group given the large variability present in the outcome measures. It is
also possible that the exercises performed in the TE program had imparted comparable joint
loads to the YE program. In the future, it would be interesting to conduct biomechanical
analysis of the exercises included in the TE program in addition to the YE program.
Congruence with previous studies
The effectiveness of land-based exercise for improving pain, physical function, and quality of
life is well-established. A large-scale review of 44 studies demonstrated high quality evidence
that land-based exercise yields a 12% (95% CI, 10±15) absolute and 27% (95% CI, 21±32)
relative improvement in pain for individuals with knee OA [
]. This meta-analysis also included
44 studies providing moderate quality evidence suggesting a 10% (95% CI, 8±13) absolute and
26% (95% CI, 20±32) relative improvement in physical function for those who engage in an
exercise intervention. Lastly, there was high quality evidence that a 4% (95% CI, 2±5) absolute
and 9% (95% CI, 5±13) relative improvement could be expected in quality of life following an
exercise program. The findings of the current study are consistent with this evidence. Pain
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(ICOAP total score), a 24% absolute and 53% relative improvement was observed in YE. There
was a 15% absolute and 34% relative improvement in TE; and a 4% absolute and 8% relative
improvement in NE. These trends were similar for secondary outcomes self-reported physical
function and mobility performance. The TE intervention in this study was designed to reflect
the current exercise prescription for knee OA, which was very similar to the majority of the
studies reviewed in the meta-analysis [
]. Not surprisingly, the magnitude of change in pain,
self-reported function, and quality of life in the TE group was similar to those values presented
in the review, in some cases slightly larger. The magnitude of improvement in the YE group
was substantially larger however. Improvements in pain and mobility performance also
exceeded those reported in a recent study, which compared changes in self-reported and
objective measures following either a 12-week leg-based or hip-based strengthening program
in older adults with knee OA [
]. In the leg-based exercise program, KOOS pain improved a
mean of 14.95 (95% CI, 9.34 to 20.56; p<0.01) which was a smaller improvement than that
seen in the YE group (mean, 21.5; p<0.017), while larger than that in the TE group (mean
difference, 21.5; p<0.017) in the current study. However, improvements in mobility
performance, particularly the 6MWT were larger in both YE (mean difference, 59.3 m; p<0.017) and
TE (mean difference, 54.0 m; p<0.017) groups compared to this recent research (mean
difference, 26.0 m; N.S.). This improvement in the 6MWT distance was also larger than those
reported in another recent study that compared 6 weeks of low intensity supervised (mean
difference, 30 m; p = 0.007) versus home-based (mean difference, 30 m; p = 0.022) strengthening
exercises in a population with knee OA [
The improvements in pain, self-reported physical function, and mobility performance in
the YE group are consistent with our previous work and other studies investigating yoga for
]. However, there is ample evidence, including our previous cohort study [
that strength increases are achievable in knee OA [
]. Thus, it was surprising there were no
significant improvements in the YE group. Lower extremity muscle strength, especially that of
the quadriceps, is an important topic in knee OA rehabilitation [
] and is of great interest to
researchers. It is not however what individuals living with knee OA find most troubling; the
pain and disability associated with the disease is of greater concern [
]. These data provide
evidence that increases in muscle strength are not necessary to elicit improvements in
symptoms of knee OA.
Contribution to the literature
This trial and the previous cohort study [
] are the first exercise interventions designed and
tested specifically to minimize potentially harmful biomechanical loads incurred by the OA
affected knee joint. Previous exercise prescriptions have not been designed using measures of
knee mechanics known to influence knee OA progression. We now have concrete evidence
that, in those with knee OA, exposure to large KAMs is linked with increased degradation of
joint tissues [5±8]. This is a concern because exercise is effective in ameliorating symptoms
with regular, chronic engagement, not on an acute basis. To ensure individuals with knee OA
are not compromising their joint health with exercise, the mechanical loading aspect of such
physical activity cannot be disregarded. Though small, this is the first RCT to conduct a direct
comparison of traditional exercise to a program designed to minimize KAM exposure.
This biomechanically-based yoga intervention appears to be well tolerated and shows promise
as an efficacious approach to alleviate the major burdening symptoms of clinical knee OA in
women. Yoga, as delivered here, appears to be similarly efficacious to traditional exercise for
14 / 18
improving pain, self-reported physical function, and quality of life. However, while the yoga
program demonstrated benefits for pain and self-reported function compared to no exercise, it
did not elicit improvements in objective measures, namely strength and mobility performance
in the between-group analyses. Further, given that the yoga program did not outperform the
traditional program in the outcomes measures recorded in this sample, future trials of yoga for
knee OA with larger samples are warranted to establish effectiveness; as well as investigate
superiority and less harm relative to traditional modes of exercise.
S1 Checklist. CONSORT 2010 checklist of information to include when reporting a
S1 Protocol. Study protocol.
Conceptualization: Jonathan D. Adachi, Michael D. Noseworthy, Monica R. Maly.
Data curation: Emily G. Wiebenga, Monica R. Maly.
Formal analysis: Alexander B. Kuntz, Jaclyn N. Chopp-Hurley, Monica R. Maly.
Funding acquisition: Jonathan D. Adachi, Michael D. Noseworthy, Monica R. Maly.
Investigation: Alexander B. Kuntz, Jaclyn N. Chopp-Hurley, Elora C. Brenneman, Sarah
Karampatos, Emily G. Wiebenga, Monica R. Maly.
Methodology: Alexander B. Kuntz, Jaclyn N. Chopp-Hurley, Elora C. Brenneman, Sarah
Karampatos, Emily G. Wiebenga, Jonathan D. Adachi, Michael D. Noseworthy, Monica R.
Project administration: Alexander B. Kuntz, Jaclyn N. Chopp-Hurley, Emily G. Wiebenga,
Monica R. Maly.
Resources: Alexander B. Kuntz, Jaclyn N. Chopp-Hurley, Emily G. Wiebenga, Monica R.
Software: Monica R. Maly.
Supervision: Jaclyn N. Chopp-Hurley, Monica R. Maly.
Writing ± original draft: Alexander B. Kuntz, Monica R. Maly.
Writing ± review & editing: Alexander B. Kuntz, Jaclyn N. Chopp-Hurley, Elora C.
Brenneman, Sarah Karampatos, Emily G. Wiebenga, Jonathan D. Adachi, Michael D. Noseworthy,
Monica R. Maly.
15 / 18
16 / 18
17 / 18
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