Optimizing Physical Activity Outcomes for Veterans After Total Knee Arthroplasty
Phase: NA
Conditions: Total Knee Arthroplasty, Osteoarthritis
Sponsor: VA Office of Research and Development

 
 
 
  
 
 
 
 
 
 
 
 
 
 
Optimizing Physical Activity Outcomes After Total Knee Arthroplasty 
NCT ID (NCT03226106) 
05/18/2021 
 
 

Study Protocol  
 
I. 
Hypotheses and Specific Aims:   
The primary objective of this randomized controlled trial is to determine efficacy of physical activity behavior-change 
telerehabilitation on improving physical activity after total knee arthroplasty (TKA). 
 
Aim 1: To determine if PAB (Physical Activity Behavior-Change) intervention results in improved physical activity after 
TKA compared to the control group (CTL). Physical activity will be measured using accelerometer-based wearable 
sensors and self-reported daily activity (Life-Space Assessment)1,23. 
 
Hypothesis 1.1: The PAB group will have greater increases in accelerometer-assessed daily step count (primary 
outcome) and percent time engaged in standing & walking activity than the CTL group from PREOP to POST2 
(primary endpoint), and group differences will persist at POST3. 
 
Hypothesis 1.2: The PAB group will have greater improvements in Life-Space Assessment scores than the CTL 
group from PREOP to POST2 (primary endpoint), and group differences will persist at POST3. 
 
Aim 2: To determine if PAB intervention results in better physical function after TKA compared to the CTL group. 
Physical function will be measured with standardized performance-based (30-Second Chair-Stand Test, Timed Up-
and-Go, Six-Minute Walk Test) and self-report (Western Ontario and McMaster Universities Osteoarthritis Index 
[WOMAC] and Veterans RAND 12-Item Health Survey [VR-12]) measures.  
 
Hypothesis 2: The PAB group will have greater improvements in all functional outcomes compared to the CTL group 
at POST2 and POST3 test points, with outcomes meeting clinically meaningful thresholds. 
 
Exploratory Aim: To identify predictors underlying responsiveness to PAB rehabilitation (i.e., change in average daily 
step count) from PREOP to POST2 in the PAB group.  
 
Hypothesis 3: We expect preoperative daily step count and physical activity-related psychosocial factors (self-
efficacy, stage of change, social support, fear of falling) will be significant determinants of intervention 
responsiveness, in addition to key demographic, anthropometric, and comorbidity determinants.  
 
II. 
Background and Significance: 
 
This study is significant for Veterans with total knee arthroplasty (TKA) based on: 1) high utilization of 
TKA, 2) persistent physical activity deficits, 3) high rates of secondary health problems and costs 
following TKA, and 4) lack of guidelines for improving physical activity behavior.  
 
High Utilization of TKA Surgery 
The number of Veterans undergoing TKA is increasing. The primary indication for TKA is knee 
osteoarthritis (OA), a chronic, degenerative joint disease that disables approximately 10% of people over 
the age of 60 and compromises the quality of life of more than 20 million Americans.4 The prevalence of 
OA increases with age, with an estimated 52% of Veterans over the age of 65 having knee OA.5 As a 
result, more than 700,000 TKAs are performed each year in the United States, and this number is 
expected to increase to nearly 3.5 million per year in less than 20 years.6 
 
Persistent Deficits in Physical Activity after TKA 
While it is clear that TKA intervention is effective for reduction of knee pain, TKA and subsequent 
rehabilitation do not typically result in significantly increased physical activity.7 Energy expenditure and 
daily physical activity after TKA remain similar to pre-surgical levels.8 This lack of increase in physical 
activity is particularly troubling when considering that the amount of pre-surgical physical activity is 
significantly less for people with knee OA than those achieved by healthy individuals of similar age.9 For 
example, in our pilot research, we found “high functioning” patients with end-stage unilateral knee OA 
had 5,886 steps/day on average (see Section D.3) classifying these individuals as “low active”, which is 
indicative of functional limitation.10 The issue of low physical activity is particularly important for the VA 
health-care system, as Veteran VA users are less physically active than Veterans who obtain health 
care outside the VA.11  
 
The same pattern of persistent physical activity limitations after TKA is also seen when examining 
physical function.12,13 Even after completion of rehabilitation, walking performance outcomes remain 20-
30% lower than healthy, age-matched older adults,12,14 and more physically demanding tasks, such as 
stair climb times, are nearly 50% slower.12 Moreover, 75% of patients report difficulty negotiating stairs 

>1 year after TKA.13 In fact, 52% of TKA patients report some degree of limitation in performing 
functional tasks, compared to only 22% of age-matched subjects without knee disorders.13 Physical 
function continues to worsen over time, with patients two to three years after TKA showing accelerated 
rates of functional decline relative to expected changes.15 
 
Individuals with end-stage knee OA, requiring TKA, exhibit long-standing physical inactivity and poor 
physical function, which require targeted and tailored intervention. Despite the presence of these long-
standing behaviors, current rehabilitation efforts are directed towards acute post-operative impairments 
following TKA, such as strength and range of motion exercises. While it is clear that progressive 
strengthening and impairment-based rehabilitation are critical to recovery after TKA,16 there is also a 
clear need to address persistent physical activity behaviors with a focused intervention.  
 
High Rates of Secondary Health Problems and Costs 
There are severe negative health consequences of chronic low physical activity after TKA.8,12,17 For 
example, inactive older adults have higher mortality rates,18 higher prevalence of cardiovascular 
disease,19 and higher prevalence of metabolic syndrome than active people of similar age.20 The 
relationship between TKA and risk for negative health consequences is compounded by the underlying 
issue of OA being linked to metabolic disease. The relationship between metabolic disease and TKA is 
illustrated in the Veteran population. For example, Veterans with diabetes aged 56-65 years 
demonstrate rates of TKA that are 2.6 times higher than Veterans without diabetes.21 Importantly, a key 
thread common to chronic metabolic disease and OA is underlying sedentary lifestyles.  
For patients with knee OA, moving from sedentary to light intensity physical activity can greatly diminish 
the odds of acquiring the metabolic syndrome (OR = 0.45).20 However, the typical sedentary behaviors 
adopted by patients with lower limb OA persist after TKA and conventional rehabilitation. The interaction 
between physical activity, metabolic disease, and TKA is of foundational significance for our proposed 
study, which is designed to address the downward spiral of health by targeting improved physical activity 
behaviors. 
 
The problem of inactivity after TKA also has health cost implications. The associated medical cost for 
chronic conditions attributed to physical inactivity has been estimated at $35.3 million annually.22 The 
cost of physical inactivity likely accounts, in part, for the high costs related to TKA. The pursuit of 
strategies to reduce the cost of TKA is important, as overall costs are significant. For example, total 
Medicare expenditures for TKA procedures in 2011 exceeded $3.5 billion.23 
 
Increasing physical activity intensity is linked to improved health and quality of life outcomes for patients 
with chronic disease, such as OA, diabetes and vascular disease.24-27 For example, individuals with 
diabetes and peripheral artery disease can significantly improve gait speed and mental health scores 
with home-based walking interventions, compared to standard of care.27 Similarly, moderate- compared 
to low-intensity physical activity is linked to better cardiovascular health, blood glucose control, and 
quality of life in patients with DM.28 Furthermore, increased activity is associated with improved physical 
function, pain, and joint stiffness scores on the Western Ontario and McMasters University Osteoarthritis 
index (WOMAC) for older adults with OA.26  
 
Lack of Guidelines for Improving Physical Activity Behavior after TKA 
Conventional rehabilitation guidelines do not address chronic poor physical activity behavior after TKA. 
As a result, current rehabilitation does not 1) optimize recovery of physical function or 2) reduce long-
term health consequences of low physical activity after TKA - two major remaining challenges in 
rehabilitation. An NIH consensus statement on Total Knee Replacement stated “the use of rehabilitation 
services is perhaps the most understudied aspect of the perioperative management of TKA patients.”29 
Furthermore, “there is no evidence supporting the generalized use of any specific pre-operative or post-
operative rehabilitation intervention.”29 While evidence has emerged in the past decade for addressing 
acute impairments after surgery, substantial room remains for improving strategies targeting long-term 
outcomes following TKA. Specifically, poor physical activity after TKA could be targeted using physical 
activity behavior-change strategies.  
 
Rehabilitation strategies to improve physical activity after TKA are neither well-defined nor well-studied, 
despite objective physical activity being well below recommended levels for patients with TKA.30 
Physical activity behavior-change interventions are not included in current rehabilitation guidelines 
following TKA.16 Yet physical activity behavior-change interventions are known to benefit older adults 
with chronic diseases, including hip and knee OA.25,26 For example, older adults with lower limb OA 
improved in exercise self-efficacy and exercise minutes per week after behavior-change intervention, 
with changes persisting 12 months after intervention (effect sizes >0.67 at all time points).26 In addition, 

older adults in Medicare-sponsored physical activity programs have lower fall risk than similarly aged 
peers.31 Our pilot study data have also shown that physical activity behavior training can be effective at 
increasing physical activity and functional outcomes (See Section D.3). This proposed study seeks to 
determine the efficacy and persistence of a behavior-change effect when incorporating physical activity 
behavior training into conventional rehabilitation for Veterans after TKA.  
 
III. 
Preliminary Studies:   
 
We have conducted pilot studies to: 1) examine the current levels of physical activity for patient with TKA 
and 2) determine the initial effectiveness of the PAB intervention, which are detailed in the next sections.  
 
Physical Activity Description for Patients with TKA after Progressive Rehabilitation 
The idea for the PAB intervention was supported by our initial sub-analysis of participants from a 
recently completed randomized controlled trial (NIH R01-D065900). The intervention of the parent trial 
involved progressive resistance strengthening exercise to improve functional outcomes. The progressive 
group was compared to a group of patients receiving traditional rehabilitation after TKA. We 
hypothesized that the progressive strengthening group would demonstrate superior outcomes in terms 
of strength, functional performance, and mobility when compared to traditional rehabilitation. Within that 
study, we performed a sub-analysis to examine physical activity before and after rehabilitation in a 
subset of participants from both groups using accelerometry (ActiGraph GT3X, ActiGraph Corporation, 
Pensacola, Florida). We measured physical activity in terms of average steps per day over a one-week 
period at five time points: before (2 weeks) and after (1, 3, 6, and 12 months) surgery.  
This preliminary study showed no significant change in steps/day for the entire cohort, the traditional 
group, or the progressive strengthening group (Table 2). In other words, mode of rehabilitation 
(progressive strengthening vs. traditional) had no effect on physical activity. In fact, even with 
progressive rehabilitation, the participants with TKS only gained and average of 379 steps per day from  
the pre-operative to 12 months post-operative time points.  The lack of change in physical activity (steps/day) 
is an interesting finding, considering that the focus of the progressive strengthening was designed to improve strength 
and function outcomes. These results suggest that physical activity after TKA must be an intentional focus of 
intervention beyond targeted progressive strengthening. From these findings, we inferred that an innovative 
intervention was necessary to target the persistent physical activity behaviors after TKA.  
 
PAB Pilot Study 
We have recently completed a pilot study to test the feasibility and initial efficacy of the PAB intervention 
for people undergoing unilateral TKA. In this pilot study, the first version of our PAB intervention 
(including the behavior-change techniques of education, self-monitoring, tailored feedback, barrier 
identification, problem solving, action planning, and encouragement) was compared to an attention 
control group in which patients reported their self-assessed recovery by telephone. Each participant 
began the pilot study as they were ending conventional outpatient physical therapy. Researchers worked 
collaboratively with the PAB group participants to create physical activity action plans and promote 
problem solving for overcoming the individually identified barriers to physical activity. Each PAB 
participant was given a Fitbit wearable sensor and tablet with a Fitbit application for home use similar to 
the proposed study (see details Section D.4.5). Intervention duration was 12 weeks with remote 
sessions conducted once weekly between the participant and researcher. The attention control group 
had the same frequency and duration of contacts with the researcher over the 12 week period.  
Table 1. Daily Step Count Before and After Total Knee Arthroplasty 
Time Point 
Traditional Control  
Group  
Progressive Strengthening 
Group  
Total 
 
Pre-Operative  
5047 ± 2105 
6071 ± 2341 
5623 ± 2230 
Month 1 Post-Operative  
3201 ± 2269 ; p = 0.146 
3994 ± 2518; p = 0.257 
3598 ± 2323; p = 0.046 
Month 3 Post-Operative 
3625 ± 1170 ; p = 0.963 
5942 ± 3518; p = 0.295 
5512 ± 2633; p = 0.563 
Month 6 Post-Operative 
5704 ± 2966 ; p = 0.004 
6299 ± 2976; p = 0.857 
6001 ± 2870; p = 0.210 
Month 12 Post-Operative 
5895 ± 3150 ; p = 0.075 
6450 ± 3923; p = 0.381 
6151 ± 3385; p = 0.092 
Note: Data are presented as mean ± SD; p-values are comparisons to Pre-Operative visit. 

Results of the pilot study (n=14 per group) demonstrate the feasibility of the intervention as well as the 
potential for such an intervention to improve physical activity levels. In terms of feasibility, all participants 
in the PAB intervention group found the 
devices and periodic interactions to be 
acceptable, as measured by a 
compliance rate of 91% (days of Fitbit 
use) over the 12 week intervention. No 
adverse events were reported by any 
participant in either group. 
At the end of the 12-week intervention, 
the PAB pilot group had an increased 
step count of 1611 steps/day (PRE: 
5456 ± 3003, POST: 7067 ± 3677 
steps/day; mean ± SD) compared to 
363 steps/day in the control group 
(PRE: 5250 ± 1544, POST: 5613 ± 
2388 steps/day) (Figure 2). The PAB 
pilot group had a nearly 2 second 
improvement in the Timed Up-and-Go 
test (PRE: 9.6 ± 3.1, POST: 7.9 ± 1.9 s) 
compared to 0.6 second improvement 
in the control group (PRE: 8.9 ± 1.0, 
POST: 8.3 ± 1.1 s). The PAB pilot group 
also increased walking distance by 16.2 
m for the 6-Minute Walk Test (PRE: 
136.2 ± 37.5, POST: 152.4 ± 26.5 m) 
compared to 8.5 m in the control group (PRE: 143.9 ± 22.3, POST: 152.4 ± 25.3 m). Although under-
powered for between-group statistical comparisons, the PAB pilot group improvements represent 
medium effect sizes (Steps per day, d=0.57; TUG, d=0.43; 6MWT, d=0.70).  
The PAB pilot investigation provides initial evidence that daily step count can be improved through a 
physical activity behavior-change intervention, and these changes are associated with functional 
improvements.  However, a larger scale intervention is necessary to more definitively demonstrate 
benefits of such an intervention.  
Based on the pilot study experiences, the proposed PAB intervention includes two key alterations. First, 
the PAB intervention will be initiated two weeks after surgery to better integrate the intervention into 
conventional rehabilitation. Second, the proposed PAB intervention sessions will taper down in 
frequency from bi-weekly to once monthly across the 12-week intervention period. This approach 
provides patients opportunity to frequently interact with the therapist during the initial acquisition of the 
new behavior and promotes participant self-efficacy as they gradually assume more control of managing 
their behavior with intervention progression.  
 
IV. Research Methods 
 
A. Outcome Measure(s):   
Descriptive Variables. Baseline descriptive measures will include demographics (age, sex, education level), 
anthropometrics (height, weight, BMI), comorbidities (Functional Comorbidity Assessment32), depression 
(Geriatric Depression Scale SF33), cognition (Folstein Mini-Mental State Exam34), exercise self-efficacy (Self-
Efficacy for Exercise Scale35), exercise readiness to change (Exercise Stages of Change36), social support 
(Multidimensional Scale of Perceived Social Support37), and fear of falling (Falls Efficacy Scale-International38). 
These descriptive variables will be used as candidate predictor variables for change in accelerometer-based 
physical activity.  
 
Accelerometer-based Activity Monitoring. The primary outcome for this study will be accelerometer-based 
physical activity (average daily step count) objectively monitored for all participants over a 7-day period, at all four 
test points. Participants will wear an activPAL micro accelerometer-based sensor (PAL Technologies, Glasgow, 
UK) to measure physical activity. The activPAL sensor is a small (23.5x43x5 mm) and lightweight (10 g) device 
that uses accelerometer-derived information about thigh position to estimate daily step count and time spent in 
different body positions (e.g. sitting/lying, standing and stepping) with high level of accuracy (99-100%).39 The 
sensor will be placed in a small nitrile sleeve and wrapped with a non-allergenic water-proof dressing on the 
midline of the thigh, approximately 1/3 distance between the hip and knee. Because the activPAL is wrapped in a 
waterproof dressing, participants will be instructed to wear it at all times (including sleep) except when swimming. 
The event data file from the activPAL software will be used to determine time spent sitting/lying, standing, and 
Figure 2. PAB pilot study outcomes.  
Abbreviations: PA, physical activity; TUG, Timed Up-
and-Go test; 6MWT, 6-Minute Walk test.  

stepping per day. A customized program will convert data to a file to estimate additional metrics of sedentary 
behavior (e.g., breaks in sedentary time, average duration of sedentary bouts). Daily step count and time spent in 
sedentary positions (lying or sitting), standing, and walking (as defined by orientation of the activPAL sensor) will 
be recorded; daily averages will be taken for the total period, weekdays, and weekend days. The activPAL 
monitor has been validated in older adult populations for assessing daily step count and types of 
postures/activities in older populations.39 
 
Life-Space Assessment (LSA). The LSA is a participant-reported measure of movement within the home and 
outside community, extending to movement beyond the geographic region of the participant’s home.40 The LSA 
asks the participant to report the number of times in the previous 4 weeks that he/she has travelled outside of the 
bedroom (or room that they sleep in), and life space is evaluated in a series of levels radiating from that room: 
other rooms in the home, outside the home, within neighborhood (~1/2 mile), within town/city (5 mile), and outside 
town/city. For each level, participants are asked whether they needed assistance from another person or an 
assistive device. An LSA score is obtained for each level by multiplying the level number (1-5) by a value for 
independence (2=no assistance, 1.5=assistive device only, 1=another person) multiplied by frequency of travel in 
that area (1=<1/wk, 2=1-3x/wk, 3=4-6x/wk, 4=daily). A composite measure of life space is obtained by summing 
the LSA for each level, with scores ranging from 0 (totally bed-bound) to 120 (travelled out of town every day 
without assistance). We will also obtain simple scores of life space attained without considering frequency of 
movement. These measures will include maximal life space (range 1-5); independent life space (range 1-5), the 
highest life space attained without help from another person or assistive device; life space using assistance, the 
highest life space attained with help from another person or assistive device; and restricted life space, a 
dichotomous measure of independent life space defining individuals having restricted (e.g. confined to 
neighborhood) or unrestricted independent life space. Baker et al.41 have shown that life space composite, 
independent life space, and life space using assistance measures are highly correlated with measures of function 
and health, and thus, are most likely to be sensitive to change in the proposed intervention. The LSA has 
established validity compared with physical function, health and disability measures.42 The LSA has excellent test-
rest-reliability (ICC=0.96) and is responsive to change in community-dwelling older adults.40 
 
The Late Life Function and Disability Instrument (LLFDI). The LLFDI is a measure of self-perceived function and 
participation in everyday life will be measured using the Late Life Function and Disability Instrument (LLFDI).1,2 
The function component contains 32 questions surrounding the participant’s perceived difficulty level on certain 
functional tasks.1 The disability component consists of 16 items and participants each rate how often they do that 
item, and how limited they feel doing the activity.2 The limitation questions in the disability component are referred 
to as the Late Life Disability Instrument-Instrumental Limitation Scale (LLDI-IL) and measure the participant’s 
perceived limitations in a variety of instrumental activities of daily living (IADLs).2  Higher scores on the LLDI-IL 
indicate improved participation in home and community activities. The LLDI-IL was used to measure participation 
in 218 individuals before and 12-months following a TKA, and participants showed significant improvements in 
participation 12-months post TKA.43 Although the LLDI was developed for elderly individuals, participants post-
TKA <65 years old showed significant improvements on the LLDI-IL. However, one third of all participants still 
scored <67/100 on the LLDI-IL which indicated that they had participation restrictions 1-year and 2-years post 
TKA.43,44 
 
The Barriers to Being Active Quiz (BBAQ). Barriers to physical activity will be quantitively measured using the 
BBAQ, a 21 question self-report measure of barriers to physical activity published by the Centers for Disease 
Control and Prevention (CDC).3 Within the BBAQ, barriers to physical activity are classified into 7 subscales: lack 
of time; social influence; lack of energy; lack of willpower; fear of injury; lack of skill; and lack of resources. In a 
sample of older adults, the BBAQ has shown moderate to strong internal consistency on all 7 subscales, and high 
overall reliability.45 A score of >5 on any subscale indicates a specific barrier to physical activity.  
 
 
30-Second Chair Stand Test (30SCS). The 30SCS is a measure of functional ability and lower extremity 
strength.46,47 Participants will be instructed to stand from a seated position and return to sitting as quickly as 
possible, safely in the 30-second time frame. The chair will be a standardized height of 46 cm. Participants will be 
encouraged to not use their upper extremities for pushing, but if they are unable, hand placement on thighs will be 
allowed and documented as an adapted test result.46 The 30SCS test has excellent reliability when used with 
patients with lower limb OA, has established validity compared to other standardized measures, and is responsive 
to change with intervention.48,49 
 
Timed Up-and-Go (TUG). The TUG will be performed by participants at all test points, as a measure of basic 
mobility skill and indicator of fall risk. Participants will be instructed to rise from a chair (seat height of 46 cm), walk 

three meters, turn and return to sitting in the same chair as quickly as possible, safely.50 The TUG test has 
established cut-off scores to indicate fall risk in community dwelling older adult populations.51 In addition, the TUG 
has high levels of test-retest reliability,52 and is responsive to changes in mobility status over time.53  
 
Six-Minute Walk (6MW). The 6MW is a test of walking endurance and long-distance walking ability and is a 
commonly used measure for quantifying functional performance following TKA.54,55 Participants will be instructed 
to cover as much ground as possible during the six-minute time with rest allowed as needed, although the timer 
will continually run. Total distance traveled and total number of turns will be documented at each test. The 6MW 
has established test-retest reliability in populations with lower limb OA56 and is responsive to change during 
rehabilitation following TKA.57 
 
Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). The WOMAC assesses participant 
reported impact of OA on pain, stiffness, and disability.58 The WOMAC consists of 24 items and takes 
approximately 10 minutes for the participant to complete. The WOMAC is a valid, reliable, and responsive self-
report assessment that is recommended for use in assessing functional outcomes related to lower limb OA.58,59 
 
Veterans RAND 12-Item Health Survey (VR-12). The VR-12 is a self-report survey that takes approximately five 
minutes for participants to complete. The survey measures health-related quality of life, is commonly used as an 
outcome measure for patients with OA, and has well-established reliability and validity when used with older adult 
populations.60,61 
 
Semi-structured interviews and field notes. Semi-structured interviews will be used to discover participants’ 
perceived changes in barriers and facilitators to physical activity, as well as life participation following the PAB 
intervention. We will select up to 20 participants from the PAB group who agree to participate in semi-structured 
interviews. Selected participants will then be interviewed following randomization and at the end of the 
intervention (POST2). Interviews will occur either in person, over the phone, or through an audio-visual 
application. All interviews will be audio-recorded and transcribed verbatim. Additionally, the facilitator will take field 
notes during the interview. Field notes will be used to capture elements of the interview such as the facilitator’s 
overall impressions, facilitator’s immediate reflections, interview context, and potential nonverbal behaviors.   
 
 
COVID-Related Changes to Physical Activity.  Self-report questionnaire describing changes to physical activity 
and describing mask usage due to COVID 19.   
 
B. Description of Population to be Enrolled:   
 
100 Veterans (50 per group) will be enrolled from Denver VAMC and the University of Colorado Hospital (UCH).  
Potential participants scheduled for TKA surgery will be identified by a VAMC or UCH surgeon who will refer 
candidates for study screening. Flyers will also be provided to orthopedic surgeons and health-care providers in 
the greater Denver metro area.  Upon referral and prior to surgery, Veterans will be screened by a research team 
member, provide informed consent and participate in a pre-operative (PREOP) test session. Consent will be 
obtained face to face, or with an e-consent. The e-consent will be available to the participant prior to the consent 
discussion.  A qualified study team member will Zoom phone/video call the potential participant.  The potential 
participant will verify their identity.  The study team member will explain the consent process and that the 
participant can navigate forward and backward through the consent form pages and that they may return to the 
form if later if they want time to think about their participation.  The study team member will read the consent form 
with the participant and will answer all questions that the participant has.  The participant and the study team 
member will both sign and date the consent form and the participant will be able to download or email themselves 
a copy of the signed form.   
 
Physical activity at PREOP will be quantified as average daily step count (accelerometer-based monitors; see 
Accelerometer-based Activity Monitoring below).62 To ensure representative physical activity levels between 
groups, randomization will be stratified using two levels of PREOP step count: <5000 and ≥5000 steps/day. 
Randomization will also be stratified by decade of age. A research assistant, who is not involved in participant 
testing/intervention, will manage randomization and maintenance of intervention codes. The study will adhere to 
the CONSORT statement recommendations for reporting randomized trials (Figure 3). 

 
Inclusion criteria: 50-85 years of age at enrollment, Veteran, and planned unilateral primary TKA.  
 
Exclusion criteria: severe non-surgical limb pain (pain >5/10 on non-surgical limb with walking); unstable 
orthopedic, neurologic, or pulmonary conditions that limit physical function; unstable cardiac condition; 
uncontrolled hypertension; uncontrolled diabetes; acute systemic infection; active cancer treatment; or recent 
stroke (within 2 years). 
 
Statistical power was estimated using variability estimates from our pilot data collection, where the change in 
physical activity (steps/day) was assessed in 42 participants (21 receiving intervention, 21 attention control) 
following TKA. The observed SD of percent change after 3 months of intervention for the pilot sample was 42%, 
with an effect size of d=0.64. This effect size equates to a detectable difference of 1,611 steps per day between 
groups. Based on this expected group difference, a 2-sample, 2-sided t-test at the 5% level with 80 patients (40 
per group) would have 80.7% power to detect a group difference. We will enroll 100 participants (50 per group) to 
allow for a ~20% loss to follow-up. Previous clinical trials in our laboratory, for patients with TKA, have resulted in 
dropout rates of 4.9% and 6.5% at 3 months post-op and 8.2% and 15.2% at 12 months. Therefore, we are 
conservatively estimating a dropout rate of 20% at 9 months.  
 
 
C. Study Design and Research Methods   
 
This is a single-blind, randomized controlled trial with 100 Veterans scheduled to have unilateral primary TKA at 
the Denver VAMC or UCH. The two study arms will be physical activity behavior-change (PAB) and attention 
control (CTL). Researchers collecting data will be blinded to group assignment.  
 
Conventional TKA rehabilitation at the Denver VAMC and at the University of Colorado Hospital consists of a total 
of 20-24 combined inpatient and outpatient visits. To ensure the total number of rehabilitation interactions in the 
proposed study is comparable to conventional rehabilitation, a total of 14 conventional rehabilitation visits 
(inpatient and outpatient) will be combined with 10 telerehabilitation sessions for 24 total rehabilitation interactions 
in both groups.  
 
Figure 3. Anticipated CONSORT Flow Diagram 

Physical Activity Behavior-Change (PAB) Intervention 
The PAB intervention will be integrated into the current evidence-based conventional rehabilitation following TKA 
(Figure 4 and Appendix 6). The PAB intervention will begin at the start of Week 3 Post-TKA and consist of a total 
of 10 participant/therapist telerehabilitation sessions (30 minutes each). The telerehabilitation sessions will occur 
using video-based interactions with computer tablets provided by the VA, to ensure Veteran confidentiality 
standards are met. One week prior to the first PAB session, a VA WOC physical therapist who specializes in 
behavior-change intervention will perform a home visit to provide each PAB participant with a Fitbit wearable 
sensor and feedback tablet for the Fitbit, along with the telerehabilitation tablet. The therapist will also perform a 
home-safety check (Appendix 7). The Fitbit wearable sensor is designed specifically to provide user visual 
physical activity feedback through an application on the feedback tablet. Fitbit use instructions will be provided 
verbally and in written form (Appendix 8). The Fitbit application will provide the participant feedback on the 
number of steps he/she has taken during daily living activity and progress toward physical activity goals.  
 
The first week of using the Fitbit activity sensor will be an accommodation period for the participant to interact with 
the equipment and establish his/her baseline for self-monitoring daily step count. The telerehabilitation tablets will 
provide the means for remote video interactions between the participant and therapist. The participant will then 
work with the therapist in the 30-minute video-based telerehabilitation sessions on participant-tailored functional 
action plans. Each plan will be based on the tailored physical activity feedback provided by the Fitbit sensor. The 
10 PAB sessions will be tapered between Week 3 and Week 14 Post-TKA: Week 3 twice weekly (2 sessions), 
Weeks 4-9 once weekly (6 sessions), and Weeks 10-14 once every other week (2 sessions). The therapist will 
systematically address the seven components of PAB intervention: education, self-monitoring, feedback, barrier 
and facilitator identification, problem solving, action planning, and encouragement (Table 3 and Appendix 6) with 
varying levels of time focused on each of these components as the intervention progresses. The therapist will also 
document health visits, falls, knee pain, and medication changes at each telerehabilitation session. 
 
Control (CTL) Intervention  
The CTL group will perform all of the conventional inpatient and outpatient visits following TKA, just as the PAB 
group (Appendix 8). Some conventional outpatient visits will occur at the Colorado Springs VA Clinic.  CTL group 
telerehabilitation sessions will match the frequency and duration of PAB group. The CTL group sessions will focus 
on education related to non-behavioral aspects of health. Education will be systematically delivered by the 
Table 2. PAB Intervention Overview 
Intervention 
Technique 
Progression from Therapist Coaching to Participant Self-Management 
Education 
Therapist delivers education topic*        
(e.g., Self Monitoring, Problems Solving, 
Identifying Barrier/Facilitators, Action 
Plans)  
Participant reports most important 
information learned. 
Self Monitoring 
Therapist guides participant in tracking 
daily step count patterns since last visit.  
Participant tracks daily step count 
trends weekly and over the course of 
intervention. 
Tailored Feedback 
Therapist leads collaborative review of 
step count data for action plan goal 
setting. 
Participant leads review of step count 
and other physical activity goals. 
Barrier / 
Facilitator 
Identification 
Therapist guides participant to identify 
barriers/facilitators of goal attainment. 
Participant self-identifies barriers and 
facilitators for goal attainment. 
Promotion of Problem 
Solving 
Collaborative generation of solutions to 
overcome barriers to goal attainment. 
Participant generates solutions to 
identified barriers to goal attainment 
Action Planning 
Collaborative activity goal 
generation.Therapist guides, using 
3% increase from daily steps from 
previous week target. 
Participant-led weekly goal 
generation. Therapist ensures 
independence in action planning. 
Encouragement 
Therapist reviews plan for the next 
week, while encouraging participant 
on successes attained toward 
improved physical health. 
Participant leads the review of the 
plan for upcoming week. 
* Each week will have a specific ‘take home’ message linking physical activity and movement behavior to 
health. Messages will be brief and based on research evidence. 
 

therapist using the telerehabilitation tablets with the following topics: Sessions 1-2) Pain Management; Sessions 
3-4) Home Safety; Sessions 5-6) Diet; Sessions 7-8) Medication Management; Sessions 9-10) Falls & Fractures 
(Appendix 8). In addition, the therapist will document health visits, falls, knee pain, and medication changes at 
each telerehabilitation session. The participant/therapist video-based telerehabilitation sessions will be semi-
scripted with the same duration (30 min.) and same tapered schedule as the PAB group. In this manner, the study 
design controls for attention and volume of rehabilitation intervention. Telerehabilitation sessions will be 
conducted by therapists who may be physically present on the Anschutz Medical Campus.  Some 
telerehabilitation sessions from both the PAB group and the CTL group may be audio recorded for interventionist 
fidelity checks. 
 
Data Collection and Outcomes 
Preoperative testing will occur 2 weeks prior to TKA (PREOP). Postoperative testing will occur midway through 
the PAB intervention (POST1), at the end of PAB intervention (POST2), and 24 weeks after PAB intervention 
(approximately 9-months after TKA) (POST3). The POST1 test will assess early between-group responses to 
intervention, while the POST2 test will assess group differences at intervention end (Primary End Point). The 
POST3 test is critical, as a key component to assessing success of behavior change is the long-term persistence 
of behavior change. Each test session will include the standardized procedures described in the next sections. 
Importantly, all test sessions occur at participant homes, to eliminate time and travel burdens for the participants 
and minimize barriers for rural participants. The 30-Second Chair Stand Test andTimed-up-and Go may be 
conducted remotely via video call and surveys may be conducted via phone/video call or through REDCap.  
Semi-structured interviews will occur following randomization, and again following the POST2 assessment period. 
Up to 20 participants will be randomly selected from the PAB group to have at least 10 paticipants participate in 
semi-structured interviews at both time points. An interview guide will be used with questions regarding the PAB 
program, perceptions of barriers and facilitators to physical activity, and perceptions of participation in everyday 
life. Depending on participant preference the interview can occur in-person, over the phone, or via an audio-visual 
application. All interviews will be audiorecorded and transcribed verbatim by a research team member or an 
approved transcription service.  
  
D. Description, Risks and Justification of Procedures and Data Collection Tools: 
 
Anticipated adverse events include medical complications due to the complex medical conditions of the older 
Veteran population and the surgical procedure prior to the intervention. Although no increase rate of falls was 
seen in the pilot study, we also anticipate increased exposure to fall risk due to increased exposure to physical 
activity. As such, a Safety Officer, Dr. Susan Ladley, experienced in clinical trial safety outcome measures will 
meet with the PI quarterly to review study progress and adverse events. Fall risk will be monitored using the TUG 
test and Falls Efficacy Scale-International (FES-I)63 at all test points (PREOP, POST1, POST2, POST3). Also, 
occurrence of falls will be recorded at each weekly visit for both the PAB and CTL groups. Fall occurrences 
(injurious and non-injurious) and other adverse events will be reported on a quarterly basis to the Safety Officer. 
The incidence of falls, defined as “inadvertently coming to rest on the ground, floor or other lower level, excluding 
intentional change in position,”64 will be of particular focus. All study-related falls (possibly, probably, or definitely) 
will be tracked. If the total number of falls reaches 5, the Safety Officer will review incidence by group. If the 
number of injurious falls for the intervention group exceeds that of the control group by 5 (5% of enrollment) at 
any time, the study will be suspended until an evaluation of study relatedness for each incidence is performed by 
the Safety Officer. Also, some questions may make subjects feel uncomfortable. There is a rare but significant 
risk of loss of confidentiality. There are also risks that are unknown at this time.    
 
E. Potential Scientific Problems:   
 
Potential for dosing of intervention to be specific to participant. Standardizing the number of visits for all 
participants allows us to control the intervention dose for the PAB intervention. We acknowledge that not all 
patients will necessarily require the same number and frequency of visits to achieve an optimal response to the 
intervention. However, our pilot study data and previous literature in other populations support the 10 visits that 
will be used in the current intervention.65 We expect our exploratory analysis will identify key determinants of 
responsiveness, which then can be used to help better dose the PAB intervention to individual patients in future 
studies of clinical implementation. 
 
Missing data. All participants with outcome measurements will be included in the intent-to-treat analysis. Although 
the protocol encourages participants to be fully compliant with the assigned intervention and testing sessions, no 
one will be dropped from follow-up measurements for lack of compliance. We will make every effort to prevent 
missed intervention sessions and test visits. Figures examining the pattern of missing data will be created to 
provide insight into the mechanism of the missingness and guide the analysis in an appropriate manner. If the 

data are missing completely at random, analyses of complete cases will provide unbiased parameter estimates; 
provision for missing data due to dropout has been accounted for in the sample size justification. If the data are 
missing at random, valid analyses may still be performed using a likelihood-based analysis of all available data, 
still generating unbiased parameter estimates. 
 
F. Data Analysis Plan:   
 
The primary outcome for this study is average number of steps taken per day, as measured by accelerometer-
based wearable sensors (activPAL) over a 7-day period at the end of the intervention. This time point is chosen 
for clinical relevance to establish efficacy of the intervention. Sustainability will be tested as a secondary outcome, 
by assessing steps taken per day six months after conclusion of the intervention period. Other secondary 
outcomes include time spent in standing/walking activities and physical function measures. Preliminary 
descriptive and graphical analyses (including boxplots, scatterplots, profile plots of change over time) will be used 
for data cleaning, data visualization, and assessing statistical assumptions.  
 
Primary Analysis (Aim 1): The primary analysis will be an intent-to-treat comparison of the differences between 
the study groups (PAB and CTL) in the change average daily step count from PREOP to POST2 (primary 
endpoint). Statistical inference will be based on the estimated coefficient for the group variable using an analysis 
of covariance (ANCOVA) model with change in average daily step count from PREOP to POST2 as the response 
variable. Additional covariates include the stratification variables (PREOP physical activity and age) to improve 
the precision of the estimate. The conclusion about group differences will be made based on this single statistical 
test to control the type I error rate at 0.05. A similar between-group analysis will be performed on the change in 
daily step count from PREOP to POST3 (6-month effect post-intervention). A sensitivity analysis will be done to 
evaluate whether conclusions would differ when other covariates are added to the model (e.g., demographics, 
anthropometrics, comorbidities, psychosocial factors). 
 
Secondary Analyses (Aims 1 & 2): Differences between study groups in the secondary outcomes of 1) time spent 
in standing/walking activity (activPAL) and 2) physical function (performance-based and self-reported outcomes), 
from PREOP to POST2 will be analyzed as described above for the primary analysis. All outcomes will also be 
analyzed at POST3 to evaluate the long-term sustainability of the PAB intervention. We anticipate that the 
secondary outcomes will be correlated with the primary outcome, and would interpret the results from the 
secondary analysis as reinforcing the findings in the primary outcome. Failure to observe consistency between 
primary and secondary outcomes will be interpreted as evidence that the effects of the PAB intervention are not 
clear, and that further study is necessary to resolve inconsistencies. This approach reduces the risk of false-
positive conclusions resulting from multiple statistical tests. 
 
Exploratory Analysis (Exploratory Aim): The exploratory analysis will delineate the mechanisms underlying 
responsiveness to the PAB intervention by using multiple linear regression to identify key predictors of average 
daily step count from PREOP to POST2 in the PAB group. We will use the approach of fitting all possible models 
to identify the most parsimonious model predictive of the primary outcome of changes in steps per day across the 
intervention period. Candidate predictor variables will be those with theoretical evidence of predicting physical 
activity, including: PREOP steps per day, demographics (age, sex, education level), anthropometrics (height, 
weight, BMI), and comorbidities (Functional Comorbidity Assessment). In addition, we will focus specifically on 
physical activity–related psychosocial factors (depression, exercise self-efficacy, exercise readiness to change, 
social support, and fear of falling). The set of candidate predictor variables will be assessed for collinearity (and 
any collinearity reduced to the extent possible) before beginning model selection procedures. With k predictor 
variables, there are 2k possible regression models.  Each of the 2k models will be fit and both 1) the adjusted R2 
and 2) Mallows’ Cp statistic will be generated for each model.  A plot of Mallows’ Cp vs p+1 (where p = the number 
of model parameters) will be used to identify parsimonious candidate models according to Hocking’s criterion. The 
best candidate models will be compared using their statistical properties as well as subject knowledge expertise 
and practical considerations (e.g. an objective variable may be preferred over a subjective variable). A final model 
will be selected from the candidate models. We hypothesize that baseline average steps per day at PREOP and 
all included psychosocial factors will be significant determinants of intervention responsiveness. The results of this 
exploratory aim will provide evidence for clinicians in determining the prognosis of patients in terms of likely 
physical activity improvement from the PAB intervention. We hypothesize that the PAB intervention will effectively 
increase physical activity, as measured in average steps per day. Whether that hypothesis is proven or not, the 
exploratory aim will add to the current body of rehabilitation knowledge by identifying key predictors of future 
activity based on baseline variables.  
 
Qualitative Analysis (Exploratory Aim). Pragmatic qualitative analysis will be used to analyze data from the semi-
structured interviews. Savin-Baden66 outlined three steps to pragmatic qualitative research: (1) visually familiarize 
yourself with the data by reading the transcripts, then identify primary categories, (2) generate conclusions, and 

(3) check the results. The 14 domains of the Theoretical Domains Framework (TDF) will be used as a priori codes 
to classify the barriers and facilitators discussed by participants. The 14 domains in the TDF are: knowledge; 
skills; social/professional role and identity; beliefs about capabilities; optimism; beliefs about consequences; 
reinforcement; intentions; goals; memory, attention, and decisions processes; environmental context and 
resources; social influences; emotion; and behavioral regulation.67 The TDF domains will be used to as “primary 
categories” (i.e. a priori codes) to capture participants’ responses to barriers and facilitators of physical activity 
(step 1 in pragmatic qualitative analysis). The researcher will then read through the coded data as well as the 
data that was not coded to generate conclusions and construct themes related to perceived barriers and 
facilitators to physical activity and changes throughout the PAB program (step 2). Finally, the themes and raw 
data supporting each theme will be reviewed by the researcher with attention to accurate representation of 
participants’ perception of barriers and facilitators (step 3). To enhance rigor we will consider procedures to 
promote credibility, consistency, and transferability.68 First, to ensure credibility we will triangulate between data 
sources (interviewers notes, transcripts, and interdisciplinary discussion). Second, to enhance consistency, the 
researcher who is coding will keep an audit trail of all decisions related to coding, interpretation, and constructed 
themes. Third, we will randomly select up to 20 participants from the PAB group to ensure maximal variation in 
PAB group experience, and the experience of potential barriers and facilitators to physical activity.  
 
 
Data analysis will be conducted with de-identified data on the Anschutz Medical Campus. 
 
G. Summarize Knowledge to be Gained:   
 
This study is an essential step for providing foundational evidence to support the effectiveness of a 
telerehabilitation approach aimed to increase physical activity in patients with TKA. The ultimate goal 
of this research line is to 1) develop and refine methods for implementing findings of the current 
study into clinical rehabilitation practice and 2) effectively disseminate these intervention methods to 
clinical institutions, both nationally and internationally. We will work with the Denver GRECC to 
develop strategies for operational partnerships both locally and nationally through Home Based 
Primary Care programs and through connections with other GRECC Associate Directors for Clinical 
Programs. In addition, Dr. Stevens-Lapsley has developed strong working collaborations with the 
Center for Research in Implementation Science and Prevention (CRISP) at the University of 
Colorado Denver to facilitate additional strategies for rapid transition to implementation strategies 
immediately upon conclusion of the proposed investigation. 
 
Personalized Rehabilitation to Optimize Utilization. Current rehabilitation guidelines after TKA are 
generalized based on population expectations.69 However, there is high individual variability within 
the population of Veterans undergoing TKA and thus, we expect variable responses to rehabilitation. 
By identifying the key predictors of responsiveness to intervention, we expect the results of our study 
to lead to methods for individually tailored approaches to personalize rehabilitation practices, which 
will optimize Veteran outcomes and lower overall costs.  
 
Application of Findings to Other VA Populations. Future investigations could apply the proposed 
PAB rehabilitation to other populations with chronic physical activity deficits. We expect our findings 
to be generalizable to a variety of populations of Veterans who are routinely seen for orthopedic 
surgeries and other medical conditions. We chose to initially focus on TKA because of the high 
utilization of TKA, the great need to improve physical activity in these Veterans, and the ability to 
capitalize on the “teachable moment” of elective TKA surgery. 
 
 

 
 H. References: 
 
 
 
1. 
Haley SM, Jette AM, Coster WJ, et al. Late Life Function and Disability Instrument: II. Development and 
evaluation of the function component. The Journals of Gerontology Series A: Biological Sciences and Medical 
Sciences. 2002;57(4):M217-M222. 
2. 
Jette AM, Haley SM, Coster WJ, et al. Late life function and disability instrument: I. Development and evaluation 
of the disability component. The Journals of Gerontology Series A: Biological Sciences and Medical Sciences. 
2002;57(4):M209-M216. 
3. 
Center for Disease Control and Prevention. Barriers to Being Active Quiz.  
https://www.cdc.gov/diabetes/ndep/pdfs/8-road-to-health-barriers-quiz-508.pdf. 
4. 
Buckwalter JA, Saltzman C, Brown T. The impact of osteoarthritis: implications for research. Clin Orthop Relat 
Res. 2004(427 Suppl):S6-15. 
5. 
Dominick KL, Golightly YM, Jackson GL. Arthritis prevalence and symptoms among US non-veterans, veterans, 
and veterans receiving Department of Veterans Affairs Healthcare. J Rheumatol. 2006;33(2):348-354. 
6. 
Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip and knee arthroplasty in the 
United States from 2005 to 2030. J Bone Joint Surg Am. 2007;89(4):780-785. 
7. 
Vissers MM, de Groot IB, Reijman M, Bussmann JB, Stam HJ, Verhaar JA. Functional capacity and actual daily 
activity do not contribute to patient satisfaction after total knee arthroplasty. BMC Musculoskelet Disord. 
2010;11:121. 
8. 
Hayes DA, Watts MC, Anderson LJ, Walsh WR. Knee arthroplasty: a cross-sectional study assessing energy 
expenditure and activity. ANZ journal of surgery. 2011;81(5):371-374. 
9. 
de Groot IB, Bussmann JB, Stam HJ, Verhaar JA. Actual everyday physical activity in patients with end-stage hip 
or knee osteoarthritis compared with healthy controls. Osteoarthritis and cartilage / OARS, Osteoarthritis 
Research Society. 2008;16(4):436-442. 
10. 
Tudor-Locke C, Bassett DR, Jr. How many steps/day are enough? Preliminary pedometer indices for public 
health. Sports medicine. 2004;34(1):1-8. 
11. 
Littman AJ, Forsberg CW, Koepsell TD. Physical activity in a national sample of veterans. Medicine and science in 
sports and exercise. 2009;41(5):1006-1013. 
12. 
Walsh M, Woodhouse LJ, Thomas SG, Finch E. Physical impairments and functional limitations: a comparison of 
individuals 1 year after total knee arthroplasty with control subjects. Phys Ther. 1998;78(3):248-258. 
13. 
Noble PC, Gordon MJ, Weiss JM, Reddix RN, Conditt MA, Mathis KB. Does total knee replacement restore 
normal knee function? Clin Orthop Relat Res. 2005(431):157-165. 
14. 
Moffet H, Collet JP, Shapiro SH, Paradis G, Marquis F, Roy L. Effectiveness of intensive rehabilitation on 
functional ability and quality of life after first total knee arthroplasty: A single-blind randomized controlled trial. 
Arch Phys Med Rehabil. 2004;85(4):546-556. 
15. 
Ritter MA, Thong AE, Davis KE, Berend ME, Meding JB, Faris PM. Long-term deterioration of joint evaluation 
scores. J Bone Joint Surg Br. 2004;86(3):438-442. 
16. 
Westby MD, Brittain A, Backman CL. Expert consensus on best practices for post-acute rehabilitation after total 
hip and knee arthroplasty: a Canada and United States Delphi study. Arthritis care & research. 2014;66(3):411-
423. 
17. 
de Groot IB, Bussmann HJ, Stam HJ, Verhaar JA. Small increase of actual physical activity 6 months after total hip 
or knee arthroplasty. Clin Orthop Relat Res. 2008;466(9):2201-2208. 
18. 
Rizzuto D, Fratiglioni L. Lifestyle factors related to mortality and survival: a mini-review. Gerontology. 
2014;60(4):327-335. 
19. 
Gill JM, Malkova D. Physical activity, fitness and cardiovascular disease risk in adults: interactions with insulin 
resistance and obesity. Clin Sci (Lond). 2006;110(4):409-425. 
20. 
Liu SH, Waring ME, Eaton CB, Lapane KL. Association of objectively measured physical activity and metabolic 
syndrome among U.S. adults with osteoarthritis. Arthritis Care Res (Hoboken). 2015. 
21. 
King KB, Findley TW, Williams AE, Bucknell AL. Veterans with diabetes receive arthroplasty more frequently and 
at a younger age. Clin Orthop Relat Res. 2013;471(9):3049-3054. 

22. 
Garrett NA, Brasure M, Schmitz KH, Schultz MM, Huber MR. Physical inactivity: direct cost to a health plan. Am J 
Prev Med. 2004;27(4):304-309. 
23. 
Nwachukwu BU, McCormick F, Provencher MT, Roche M, Rubash HE. A comprehensive analysis of Medicare 
trends in utilization and hospital economics for total knee and hip arthroplasty from 2005 to 2011. J 
Arthroplasty. 2015;30(1):15-18. 
24. 
Colberg SR, Sigal RJ, Fernhall B, et al. Exercise and type 2 diabetes: the American College of Sports Medicine and 
the American Diabetes Association: joint position statement executive summary. Diabetes care. 
2010;33(12):2692-2696. 
25. 
Schlenk EA, Lias JL, Sereika SM, Dunbar-Jacob J, Kwoh CK. Improving physical activity and function in overweight 
and obese older adults with osteoarthritis of the knee: a feasibility study. Rehabilitation nursing : the official 
journal of the Association of Rehabilitation Nurses. 2011;36(1):32-42. 
26. 
Hughes SL, Seymour RB, Campbell RT, et al. Long-term impact of Fit and Strong! on older adults with 
osteoarthritis. The Gerontologist. 2006;46(6):801-814. 
27. 
Collins TC, Lunos S, Carlson T, et al. Effects of a home-based walking intervention on mobility and quality of life 
in people with diabetes and peripheral arterial disease: a randomized controlled trial. Diabetes care. 
2011;34(10):2174-2179. 
28. 
Goodwin VA, Richards SH, Taylor RS, Taylor AH, Campbell JL. The effectiveness of exercise interventions for 
people with Parkinson's disease: a systematic review and meta-analysis. Movement disorders : official journal of 
the Movement Disorder Society. 2008;23(5):631-640. 
29. 
Consensus Panel NIH. NIH Consensus Statement on total knee replacement December 8-10, 2003. J Bone Joint 
Surg Am. 2004;86-A(6):1328-1335. 
30. 
Paxton RJ, Melanson EL, Stevens-Lapsley JE, Christiansen CL. Physical activity after total knee arthroplasty: A 
critical review. World journal of orthopedics. 2015;6(8):614-622. 
31. 
Greenwood-Hickman MA, Rosenberg DE, Phelan EA, Fitzpatrick AL. Participation in Older Adult Physical Activity 
Programs and Risk for Falls Requiring Medical Care, Washington State, 2005-2011. Preventing chronic disease. 
2015;12:E90. 
32. 
Groll DL, To T, Bombardier C, Wright JG. The development of a comorbidity index with physical function as the 
outcome. J Clin Epidemiol. 2005;58(6):595-602. 
33. 
Hoyl MT, Alessi CA, Harker JO, et al. Development and testing of a five-item version of the Geriatric Depression 
Scale. J Am Geriatr Soc. 1999;47(7):873-878. 
34. 
Folstein MF, Folstein SE, McHugh PR. "Mini-mental state". A practical method for grading the cognitive state of 
patients for the clinician. Journal of psychiatric research. 1975;12(3):189-198. 
35. 
Resnick B, Jenkins LS. Testing the reliability and validity of the Self-Efficacy for Exercise scale. Nursing research. 
2000;49(3):154-159. 
36. 
Degischer S, Labs KH, Hochstrasser J, Aschwanden M, Tschoepl M, Jaeger KA. Physical training for intermittent 
claudication: a comparison of structured rehabilitation versus home-based training. Vasc Med. 2002;7(2):109-
115. 
37. 
Zimet GD, Powell SS, Farley GK, Werkman S, Berkoff KA. Psychometric characteristics of the Multidimensional 
Scale of Perceived Social Support. Journal of personality assessment. 1990;55(3-4):610-617. 
38. 
Delbaere K, Close JC, Mikolaizak AS, Sachdev PS, Brodaty H, Lord SR. The Falls Efficacy Scale International (FES-I). 
A comprehensive longitudinal validation study. Age Ageing. 2010;39(2):210-216. 
39. 
Taraldsen K, Askim T, Sletvold O, et al. Evaluation of a body-worn sensor system to measure physical activity in 
older people with impaired function. Phys Ther. 2011;91(2):277-285. 
40. 
Baker PS, Bodner EV, Allman RM. Measuring Life-Space Mobility in Community-Dwelling Older Adults. Journal of 
the American Geriatrics Society. 2003;51(11):1610-1614. 
41. 
Baker PS, Bodner EV, Allman RM. Measuring life-space mobility in community-dwelling older adults. J Am Geriatr 
Soc. 2003;51(11):1610-1614. 
42. 
Peel C, Baker PS, Roth DL, Brown CJ, Bodner EV, Allman RM. Assessing Mobility in Older Adults: The UAB Study 
of Aging Life-Space Assessment. Physical therapy. 2005;85(10):1008-1019. 
43. 
Maxwell JL, Keysor JJ, Niu J, et al. Participation following knee replacement: the MOST cohort study. Physical 
therapy. 2013;93(11):1467-1474. 

44. 
Keysor JJ, Jette AM, LaValley MP, et al. Community environmental factors are associated with disability in older 
adults with functional limitations: the MOST study. Journals of Gerontology Series A: Biomedical Sciences and 
Medical Sciences. 2009;65(4):393-399. 
45. 
Zalewski K, Alt C, Arvinen-Barrow M. Identifying barriers to remaining physically active after rehabilitation: 
differences in perception between physical therapists and older adult patients. journal of orthopaedic & sports 
physical therapy. 2014;44(6):415-424. 
46. 
Dobson F, Hinman RS, Roos EM, et al. OARSI recommended performance-based tests to assess physical function 
in people diagnosed with hip or knee osteoarthritis. Osteoarthritis and cartilage / OARS, Osteoarthritis Research 
Society. 2013;21(8):1042-1052. 
47. 
Jones CJ, Rikli RE, Beam WC. A 30-s chair-stand test as a measure of lower body strength in community-residing 
older adults. Res Q Exerc Sport. 1999;70(2):113-119. 
48. 
Gill S, McBurney H. Reliability of performance-based measures in people awaiting joint replacement surgery of 
the hip or knee. Physiotherapy research international : the journal for researchers and clinicians in physical 
therapy. 2008;13(3):141-152. 
49. 
Gill SD, de Morton NA, Mc Burney H. An investigation of the validity of six measures of physical function in 
people awaiting joint replacement surgery of the hip or knee. Clinical rehabilitation. 2012;26(10):945-951. 
50. 
Podsiadlo D, Richardson S. The timed "Up & Go": a test of basic functional mobility for frail elderly persons. 
Journal of the American Geriatrics Society. 1991;39(2):142-148. 
51. 
Shumway-Cook A, Brauer S, Woollacott M. Predicting the probability for falls in community-dwelling older adults 
using the Timed Up & Go Test. Phys Ther. 2000;80(9):896-903. 
52. 
Lin MR, Hwang HF, Hu MH, Wu HD, Wang YW, Huang FC. Psychometric comparisons of the timed up and go, 
one-leg stand, functional reach, and Tinetti balance measures in community-dwelling older people. J Am Geriatr 
Soc. 2004;52(8):1343-1348. 
53. 
van Iersel MB, Munneke M, Esselink RA, Benraad CE, Olde Rikkert MG. Gait velocity and the Timed-Up-and-Go 
test were sensitive to changes in mobility in frail elderly patients. J Clin Epidemiol. 2008;61(2):186-191. 
54. 
Bruun-Olsen V, Heiberg KE, Wahl AK, Mengshoel AM. The immediate and long-term effects of a walking-skill 
program compared to usual physiotherapy care in patients who have undergone total knee arthroplasty (TKA): a 
randomized controlled trial. Disabil Rehabil. 2013;35(23):2008-2015. 
55. 
Bade MJ, Kohrt WM, Stevens-Lapsley JE. Outcomes before and after total knee arthroplasty compared to 
healthy adults. The Journal of orthopaedic and sports physical therapy. 2010;40(9):559-567. 
56. 
Kennedy DM, Stratford PW, Wessel J, Gollish JD, Penney D. Assessing stability and change of four performance 
measures: a longitudinal study evaluating outcome following total hip and knee arthroplasty. BMC 
Musculoskelet Disord. 2005;6:3. 
57. 
Parent E, Moffet H. Comparative responsiveness of locomotor tests and questionnaires used to follow early 
recovery after total knee arthroplasty. Arch Phys Med Rehabil. 2002;83(1):70-80. 
58. 
Bellamy N, Buchanan WW, Goldsmith CH, Campbell J, Stitt LW. Validation study of WOMAC: a health status 
instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in 
patients with osteoarthritis of the hip or knee. J Rheumatol. 1988;15(12):1833-1840. 
59. 
Howe TE, Dawson LJ, Syme G, Duncan L, Reid J. Evaluation of outcome measures for use in clinical practice for 
adults with musculoskeletal conditions of the knee: a systematic review. Manual therapy. 2012;17(2):100-118. 
60. 
Ware J, Jr., Kosinski M, Keller SD. A 12-Item Short-Form Health Survey: construction of scales and preliminary 
tests of reliability and validity. Medical care. 1996;34(3):220-233. 
61. 
Jones D, Kazis L, Lee A, et al. Health status assessments using the Veterans SF-12 and SF-36: methods for 
evaluating otucomes in the Veterans Health Administration. The Journal of ambulatory care management. 
2001;24(3):68-86. 
62. 
Tudor-Locke C, Craig CL, Thyfault JP, Spence JC. A step-defined sedentary lifestyle index: <5000 steps/day. 
Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme. 
2013;38(2):100-114. 
63. 
Yardley L, Beyer N, Hauer K, Kempen G, Piot-Ziegler C, Todd C. Development and initial validation of the Falls 
Efficacy Scale-International (FES-I). Age Ageing. 2005;34(6):614-619. 
64. 
Organization WH. WHO Global Report on Falls Prevention in Older Age. Geneva, Switzerland: World Health 
Organization;2007. 

65. 
Geraedts H, Zijlstra A, Bulstra SK, Stevens M, Zijlstra W. Effects of remote feedback in home-based physical 
activity interventions for older adults: a systematic review. Patient Educ Couns. 2013;91(1):14-24. 
66. 
Savin-Baden M, Major CH. Qualitative research: The essential guide to theory and practice. 2013. 
67. 
Atkins L, Francis J, Islam R, et al. A guide to using the Theoretical Domains Framework of behaviour change to 
investigate implementation problems. Implementation Science. 2017;12(1):77. 
68. 
Merriam SB. Qualitative Research: A Guide to Design and Implementation. Second ed. San Francisco, CA: Jossey-
Bass; 2009. 
69. 
Oatis CA, Li W, DiRusso JM, et al. Variations in Delivery and Exercise Content of Physical Therapy Rehabilitation 
Following Total Knee Replacement Surgery: A Cross-Sectional Observation Study. International journal of 
physical medicine & rehabilitation. 2014;Suppl 5. 
 
 
 
 
 
 

Statistical Analysis Plan  
 
An intention-to-treat approach was used for the primary data analysis. The two treatment arms 
were compared by demographics and baseline clinical characteristics using standardized mean difference 
and confidence intervals. Observed means of the primary and secondary outcomes were calculated. To 
assess group differences in the primary outcome (average daily step count), a linear mixed model (LMM) 
was used. The LMM accounted for the within-subject correlation associated with repeated measures 
through the inclusion of a random intercept for subject. Decade of participant age was included in the 
LMM as a continuous fixed effect. The model also included as fixed effects time and an interaction 
between intervention arm and time. Between-group difference at baseline was set at zero, so estimated 
baseline scores were equal between groups.  
The primary analysis was conducted using the first 3 time points (pre-surgery, 8 weeks post-
surgery, 14 weeks post-surgery), and the test of intervention effect on daily step count was tested using a 
Likelihood Ratio Test (LRT). P-values for the effect of intervention were derived from a LRT comparing 
the model with interaction of intervention arm and time versus the reduced model without the interaction. 
Contrasts were used to estimate group means and confidence intervals.  
Secondary and exploratory analyses used the same methods as the primary outcome (pre-surgery, 
8 weeks post-surgery, 14 weeks post-surgery, and 38 weeks post-surgery), and week 38). A secondary 
LMM analysis with the four time points was also conducted to test for group difference in daily step count 
at Week 38. All analyses were performed using R statistical software version 4.3.0.