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. 2026 Feb 25;8(2):100760. doi: 10.1016/j.ocarto.2026.100760

Weight loss and physical activity after total knee replacement: Study protocol for the Healthy Living randomized controlled trial

Christine A Pellegrini a,⁎, Sara Wilcox a,b, Clare Kennerley a, Jungwha Lee c, Gabrielle Turner-McGrievy d, Elizabeth Regan a, Phillip Wessinger e, Brian Chen f, Harley T Davis g, Scott Jamieson a, Kailyn Horn a, Melissa Stansbury a, J Benjamin Jackson III g,h
PMCID: PMC12969099  PMID: 41809760

Abstract

Background

Most people who receive a total knee replacement (TKR) are physically inactive and meet criteria for overweight/obesity, putting them at increased risk of poor functional outcomes and chronic diseases. This paper describes the protocol and procedures for the Healthy Living Study, a 12-month randomized controlled trial comparing outcomes between a patient-centered weight loss program and chronic disease self-management program in adults with TKR.

Methods

This study will aim to recruit 212 adults with overweight/obesity (body mass index [BMI] 25–45 kg/m2) who received a TKR ≤6 months previously. Participants will be randomized to either a) PACE, a 12-month telephone-based program focused on reducing calories and increasing physical activity to facilitate a 7 % weight loss or b) a Chronic Disease Self-Management (CDSM) control group which provides education on how to manage chronic diseases while avoiding content related to physical activity or diet. Assessments conducted at baseline, 6, 12 (post-intervention) and 18 months (following a 6-month no intervention period) will assess change in weight (primary outcome), physical activity, pain, and physical function. Secondary aims will examine the cost-effectiveness of PACE, as well as potential behavioral and psychosocial mediators of weight loss and TKR-related outcomes.

Conclusion

This protocol paper describes the design, rationale, and behavioral interventions for the Healthy Living randomized controlled trial which will target an important clinical population and determine whether a patient-centered weight loss program after TKR is an effective solution to improve outcomes.

Keywords: Knee arthroplasty, Behavioral intervention, Diet, Exercise, Technology

1. Introduction

Total knee replacement (TKR) utilization is rising considerably in both older [1] and younger adults [2]. As life expectancy in the US approaches 80 years, people are living longer with TKR, thus, it is critical to identify strategies that will maximize long-term functional outcomes and quality of life. Most adults with TKR meet criteria for overweight/obesity (body mass index [BMI] >25 kg/m2) [3,4] and remain physically inactive after surgery [5,6], both of which heighten the risk of poor functional outcomes [7] and disability [8]. Although TKR typically improves pain and physical function, adults who undergo the procedure face a 60 % greater risk of clinically significant weight gain compared to non-surgical peers [9]. Additionally, within the decade following surgery, adults with TKR are at higher risk for death from dementia [10] and cardiovascular disease [11] as compared to adults without TKR. While the precise causes of excess mortality in this population remain unclear [12], engaging in weight management and physical activity after TKR may mitigate continued weight gain and help prevent or delay the development of cardiovascular disease [13], dementia [14], and Alzheimer's disease [14].

To date, most weight management programs in adults with TKR have occurred before surgery [15] or focused solely on either diet [16] or physical activity behaviors [[17], [18], [19], [20]]. However, obesity treatment guidelines recommend lifestyle modification through the combination of a reduced calorie diet and increased physical activity [21]. Our preliminary findings suggest that starting a patient-centered, telephone-based behavioral weight loss program focused on improving diet and physical activity after TKR produced greater weight losses (5.4 %) than among participants starting the same 4-month program before surgery [22]. Targeting both behaviors, consistent with recommendations [23], via brief phone coaching during a teachable moment [24], may yield clinically significant outcomes and serve as a scalable model with strong potential for real-world translation. Further, with the substantial economic burden and shift to value-based care and bundled payment initiatives, low-cost and pragmatic approaches are critically needed to enhance outcomes following this elective surgery.

The purpose of this paper is to describe the Healthy Living study, a 12-month randomized controlled trial that builds on our pilot work to examine the effectiveness of a telephone-based weight loss program on short- and long-term weight loss, physical function, physical activity, and pain as compared to a control group. Secondary aims will examine the cost-effectiveness of PACE, as well as potential behavioral and psychosocial mediators of weight loss and TKR-related outcomes. Specifically, this paper focuses on describing the full details of the behavioral interventions as well as the recruitment, screening, and retention strategies.

2. Methods

2.1. Study overview

This study is a two-arm randomized controlled trial examining the effectiveness of a patient-centered multicomponent (diet and physical activity) weight loss program (PACE) in adults after TKR. Participants (N = 212) will be randomized to PACE or a Chronic Disease Self-Management program (CDSM) control group. Both programs will be delivered remotely for 12 months and include phone calls with a health coach weekly during months 1–4, biweekly during months 5–6, and monthly during months 7–12. Assessments examining changes in weight, physical function, pain, and physical activity will be completed at baseline, 6, 12 and 18 months. The study design is displayed in Fig. 1, which shows the timeline for enrollment, interventions, and assessments. All study procedures have been approved by the University of South Carolina's Institutional Review Board. The trial is registered on Clinicaltrials.gov (NCT05190666).

Fig. 1.

Fig. 1

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Study design.

2.2. Participants

This study will recruit adults (≥18 years of age) who are less than 6 months post-TKR, have a BMI between 25 and 45 kg/m2, and have no contraindications to diet, exercise, or weight loss. Full inclusion and exclusion criteria are shown in Table 1.

Table 1.

Inclusion and exclusion criteria.

Inclusion Criteria
  • -

    BMI between 25 and 45 kg/m2

  • -

    Had a knee replacement (including primary, staged or independent bilateral, or revision) < 6 months prior to baseline assessment

  • -

    Have a computer, tablet, or smartphone with active internet access

  • -

    Completed baseline assessment measures (height, weight, function tests, surveys, ≥4 valid days of physical activity monitoring, and 1 day of dietary recall)

  • -

    be English-speaking and able to read consent and study materials written in English

  • -

    be willing to attend 4 in-person assessment visits

Exclusion Criteria
  • -

    Have any contraindications to diet or weight loss

  • -

    Underwent simultaneous bilateral knee replacement or have a scheduled or anticipated knee replacement for the contralateral knee within the next 18 months

  • -

    Have a mobility limiting comorbidity unrelated to TKR (e.g., spinal stenosis, fibromyalgia, peripheral vascular disease, stroke)

  • -

    are taking anti-obesity medications

  • -

    are enrolled in a formal weight loss program

  • -

    Had or are planning to have bariatric/gastric/lap band surgery

  • -

    are planning to relocate out of the study areas in the next 18 months

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2.3. Recruitment and enrollment

Potential participants will primarily be recruited through two sites from a healthcare system in South Carolina. Recruitment strategies include placing recruitment postcards in waiting rooms and pre-operative packets, as well as notifying patients scheduled for post-TKR appointments of the study. Interested participants will be asked to complete a brief screening in-person, over the telephone, or online to assess eligibility criteria and willingness to participate. Interested and eligible individuals will then be scheduled for baseline assessments.

2.4. Baseline assessment and randomization

Prior to starting the baseline assessment, study staff will review the informed consent and use a methods-motivational interviewing approach to assist with retention [25]. During this process, the pros and cons of participating in each condition and as part of a research study overall will be discussed. Once all questions are answered, interested participants will sign the informed consent document and then start the in-person assessment. Assessments will take place at either the University of South Carolina (Columbia, SC) or Prisma Health-Upstate (Greenville, SC).

After completing the baseline assessment and ensuring all eligibility criteria are met, participants will be randomized by non-blinded staff using computer-generated schemes created by the biostatistician. Randomization, stratified by site, age (<65 years and ≥65 years), sex, and BMI (<35 and ≥ 35 kg/m2), will be on a rolling basis using randomly permuted blocks of 2 or 4 to one of two conditions in a 1:1 ratio.

2.5. Intervention

2.5.1. PACE weight loss program

PACE is a patient-centered, theory-informed lifestyle program designed to support healthy behavior change by integrating principles from the Social Cognitive Theory (SCT) [26] and Self Determination Theory (SDT) [27]. Modeled after the Diabetes Prevention Program [28] and Look AHEAD [29], PACE targets SCT [26] constructs such as self-control of performance and self-efficacy through self-monitoring, goal setting, and behavioral feedback and reinforcement. Input from patients and stakeholders further contributed to refining the program to ensure it is both relevant and engaging and tailoring behavioral strategies to meet patients' unique preferences (e.g., health coaching sessions delivered via telephone, technology-based self-monitoring) [30] and needs (e.g., education to address activity and dietary concerns after TKR, activity recommendations from physical therapists) [31]. PACE also incorporates SDT principles by fostering autonomy, competence, and relatedness. The program actively elicits patients’ perspectives, offers choices, supports decision-making, and provides consistent encouragement, all aimed at promoting intrinsic motivation and long-term engagement. Importantly, PACE is introduced at a teachable moment [24], a point in time when individuals may be more receptive to behavior change, which can further enhance motivation and adherence.

According to our conceptual model (Fig. 2), we posit that key constructs from both SCT (self-efficacy, self-control of performance, and outcome expectations) and SDT (autonomy, competence, and relatedness) will serve as pathways to enhance engagement and adherence to the PACE intervention. These improvements in engagement (e.g., completion of coaching calls) and adherence (e.g., self-monitoring of diet, activity, and weight) are expected to drive reductions in caloric intake and increases in physical activity, ultimately resulting in weight loss. In turn, weight loss is anticipated to lead to improvements in physical function and pain. All constructs included in our model have been previously associated with, or shown to mediate, weight loss outcomes in similar programs [[32], [33], [34], [35]].

Fig. 2.

Fig. 2

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Conceptual model illustrating the mechanisms by which the PACE program is expected to facilitate weight loss, improve physical function, and reduce pain.

PACE Goals. Prior research suggests that a weight loss of ≥5 % achieved through behavioral interventions is clinically meaningful; therefore, participants were given a 7 % goal to ensure clinical relevance while increasing the likelihood of observing meaningful weight loss across participants [36]. To facilitate a weight loss of 1–2 lbs. per week, a calorie goal between 1200 and 2000 kcal/day will be given based on baseline body weight aiming to create a 500–1000 kcal/day deficit [28]. Macronutrient distribution will be based on the US Dietary Guidelines [37].

Physical activity goals will align with the 2018 Physical Activity Guidelines for Adults and Older Adults and target 150–300 min/week of moderate-intensity physical activity (MPA) and muscle strengthening activities on at least 2 days/week [38]. Behavioral lessons with skill-building activities will be provided on the activity targets (Table 2). Aerobic activity goals will be tailored weekly according to participants’ current functioning after surgery and will gradually increase every 2 weeks at a rate appropriate for their ability. Starting in week 5, participants will be encouraged to perform four resistance exercise movement patterns (e.g., squat, lunge, stepping, calf raise) on 3 days/week, as recommended after knee replacement to maintain and further build strength and mobility. Photograph and video instructions for each movement pattern and exercise progressions will be provided. Further, participants will be asked to rate their effort using the modified Borg Ratings of Perceived Exertion (RPE) scale [39] and pain for each exercise.

Table 2.

Call schedule and Lesson Topics.

PACE Weight Loss (Intervention) Chronic Disease Self-Management (Control)
Week Topic
1 Welcome to PACE Welcome to Chronic Disease Self-Management
2 Be a Fat and Calorie Detective Managing Common Symptoms
3 Healthy Eating Problem Solving Skills
4 Moving those Muscles After Surgery Decision Making: Pros and Cons
5 Strengthen Your Physical Activity Plan Goal Setting
6 Taking Charge of What's Around You Developing an Action Plan
7 Barriers to Exercise After TKR Rewarding Yourself
8 Exercise Programs Based on Your Recovery Finding Resources
9 How to Get Back After a Slip Dealing with Fatigue/Sleep Hygiene
10 Eating Out at Restaurants Emotional Self-care
11 Managing Post-op Expectations Range of Motion
12 Make Social Cues Work for You Relaxation and Stress Management Techniques
13 Motivation for Weight Loss & Knee Health Making Midcourse Corrections
14 Exploring Different Types of Exercise A Breath of Fresh Air: Benefits of Nature
15 Take Charge of Your Lifestyle After Surgery Positive Thinking and Self-Talk
16 Mindful Eating, Mindful Movement Self-Management Tools to Shift your Mind and Mood
Transition to Bi-weekly Calls
18 Stand Up for Your Knee & Health Safe and Effective Stretching
20 The Weight Loss Plateau Reducing Injury
22 Being Active as a Way of Life Home Safety
24 Role of Thoughts in Weight Loss & Recovery Communication Techniques
26 Maintaining Knee Strength & Mobility Asking for Help
Transition to Monthly Calls
30 Confront Your Food Cues Social Media
34 Strategies at the Supermarket Balancing Home Life
39 Revisiting the Importance of Resistance Training Managing Screen Time
43 Holiday-Proofing your Home Time Management: Organizing your Life
47 Maintaining Activity Plans after Lapses Continuing Self-Management When the Calls Stop
52 Strategies to Maintain Weight Loss A Year Later: Where will your knee take you?
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Self-Monitoring. PACE participants will be encouraged to monitor their weight, dietary intake, and physical activity daily throughout the intervention. Based on our pilot work, technology-based self-monitoring was preferred among participants with TKR [22,30]. Thus, all participants will be provided with a Blue-tooth enabled body weight scale and Fitbit physical activity wrist-worn tracker to use during the study, which will transmit weight and physical activity data remotely to the coaching interface. Additionally, participants will be given access to FatSecret, an online or app-based dietary self-monitoring program. Participants will be encouraged to self-weigh daily using the smart scale, record their dietary intake (individual food items, portion sizes, calories, and fat), track all minutes of MPA performed as planned/intentional exercise, and report completion of resistance exercises (exercise type and level, sets and repetitions, RPE, and pain) via a weekly survey.

Telephone Coaching. Coaching calls will occur weekly during the first four months, bi-weekly during months 5–6, and monthly between months 7–12, similar to previous behavioral interventions [40,41]. Behavioral interventionists will be at least a Master's level exercise physiologist, dietitian, certified health coach, or have expertise in a related field. Behavioral interventionists will receive training on the principles of patient-centered counseling, motivational interviewing, and behavioral theories. Training on the study-specific conceptual model, TKR, resistance exercises, and procedures (i.e., confidentiality, behavioral goal setting, coaching call checklists, documentation system). During each session, behavioral interventionists will follow a checklist consistent with intervention fidelity targets. This includes checking in on participants' progress with recovery from surgery and providing feedback on participants' self-monitored data (diet, activity [aerobic and strength], and weight). Interventionists will also review pain and RPE on current levels of resistance exercises and progress when appropriate. Behavioral interventionists will help participants explore ambivalence to change and assist with problem-solving to overcome any barriers to diet, activity, or weight loss. Table 2 lists the current behavioral lesson topics informed by stakeholders. The first coaching call will last 30–45 min to allow for rapport building between coach and participant, consistent with the supportive accountability model [42], and provide detailed explanations and justifications of the program and goals. All follow-up calls will be approximately 10–15 min in duration and target theoretical constructs from the conceptual model (e.g., self-efficacy, competence).

2.5.2. Chronic disease self-management (CDSM) control group

Participants randomized to the CDSM program will receive education on a variety of topics to improve their skills in managing chronic diseases, including arthritis. This self-directed program includes brief educational lessons (Table 2) unrelated to study outcomes (e.g., relaxation, communication techniques, emotion regulation) provided on the study website and in printed format, supplemented by the book Living a Healthy Life with Chronic Conditions [43].

Similar to PACE, the CDSM group will receive calls from an interventionist weekly in months 1–4, bi-weekly in months 5–6, and monthly in months 7–12 (27 total calls). Interventionists will use a CDSM-specific checklist of topics to cover during each call consistent with intervention fidelity targets. Participants in CDSM will not receive any coaching related to diet, physical activity, or weight loss from research staff or interventionists during study calls. In the event a participant brings up one of these topics such as physical activity, study staff will be trained to redirect the topic, encourage participants to talk to a physical therapist, or remind participants of the focus of the CDSM group.

2.5.3. Maintenance period

Both groups will enter a 6-month maintenance period during months 12–18. During this time, participants will have the option to continue self-monitoring; however, interventionists will not have access to their data, provide any feedback, or contact the participant. Non-interventionist research staff will call participants each month to ask about any health issues during the previous month. All health issues and adverse events are monitored and tracked.

2.5.4. Intervention fidelity

All coaching calls will be audio recorded and saved on a secure password protected drive in which only unblinded study personnel can access. Each quarter, 15 % of calls will be randomly selected to undergo review by two independent reviewers trained on calls for intended session content (e.g., review of goal progress, self-monitoring, goal setting/action planning, positive reinforcement and behavioral lesson for PACE) and unintended content (e.g., discussion of diet, physical activity, and/or weight loss for CDSM). If scores from the two independent reviews differ by more than 10 %, a third reviewer will assess the call to resolve any discrepancies. If fidelity falls below 80 %, behavioral interventionists will be retrained. Biweekly clinical meetings led by Doctoral-level experts in clinical psychology and exercise physiology are held with all interventionists to discuss participant progress.

2.6. Retention

Retention strategies will include: (1) outlining the pros and cons of study participation prior to enrollment [44]; (2) a comprehensive plan to contact participants to complete telephone sessions and assessments (3) identification of two secondary contacts who could be contacted should study staff be unable to reach the participant [44]; and (4) Incentives ($50) for completing each in-person assessment and quarterly raffles for participants who complete all study assessments.

2.7. Aims and outcomes

The specific aims of the project are:

Aim 1: Examine the impact of the PACE weight loss program on weight (primary outcome), pain, and objectively measured physical function and physical activity at 6 months post-TKR as compared to the control condition.

Aim 2: Examine the effects of the PACE weight loss program on weight loss and improvements in physical function, pain, and physical activity at the end of treatment (12 months) and a maintenance period (18 months) as compared to the control condition.

Aim 3: Examine the cost effectiveness of the PACE weight loss program relative to the control group to improve productivity and health-related quality of life, increase quality adjusted life years, and reduce adverse healthcare utilization at 6, 12, and 18 months.

Aim 4: Examine behavioral (e.g., calls completed, adherence to self-monitoring) and psychosocial (e.g., self-efficacy, autonomy) mediators of weight loss and secondary outcomes consistent with our conceptual model.

Assessments will be completed at baseline, 6, 12, and 18 months. Participants will visit one of the study centers (Columbia or Greenville, SC) in person to complete a series of assessments led by trained assessors blinded to randomization. All questionnaires will be administered online via REDCap, a secure web platform. All electronic data will be saved on a password protected secure and all paper data will be locked in a file cabinet. Only study personnel will have access to the data. Table 3 lists the primary and secondary outcomes.

Table 3.

Study outcomes and measures.

Concept Outcome Measure
Primary and Secondary Outcomes (Aims 1 and 2)
Body Weight
  • -

    Objectively measured changes in weight (kg) between baseline and 6 (Primary outcome - Aim 1), 12 and 18 months (Aim 2)
  • -

    Calibrated electronic scale with participants wearing light clothing, no shoes, and empty pockets.
Physical function
  • -

    Objectively measured changes in physical function between baseline and 6 (Aim 1), 12, and 18 months (Aim 2)
  • -

    Six-minute walk (feet); chair stands/30 s; timed up and go (seconds) and stair climb test using Osteoarthritis Research Society International (OARSI) procedures [45]
Physical Activity
  • -

    Actigraph (GT9X Link, waist worn) measured changes in physical activity between baseline and 6 (Aim 1), 12, and 18 months (Aim 2)
  • -

    Minutes/week of moderate-intensity physical activity (≥2020 counts/min) based on ≥4 valid days of ≥10 h/day. Non-wear defined as ≥90 min with 0 counts/min, allowing up to 2 consecutive minutes of <100 counts/min [46,47] Data will be processed using ActiLife 6.
Pain
  • -

    Changes in self-reported pain between baseline and 6 (Aim 1), 12, and 18 months (Aim 2)
  • -

    Patient-Reported Outcomes Measurement Information System (PROMIS) [48] pain intensity & interference

  • -

    Western Ontario and McMaster Universities Arthritis Index (WOMAC) [49] pain scale
Cost-Effective Variables (Aim 3)
Health-Related Quality of life and Quality Adjusted Life Years (QALYs)
  • -

    Incremental cost effectiveness ratio in terms of cost per QALY gained
  • -

    SF 12v2 Health Survey [50]

  • -

    SF-6d [51]
Work productivity
  • -

    Incremental cost-effectiveness ratio in terms of work productivity
  • -

    Work Productivity and Activity Impairment Questionnaire [52]
Healthcare utilization
  • -

    Incremental cost effectiveness ratio in terms of inpatient and Emergency Department (ED) utilization
  • -

    Any inpatient admission; medication costs

  • -

    Inpatient admission related to obesity;

  • -

    Any ED visit;

  • -

    ED visit related to obesity;

  • -

    Health care expenditures for these health care visits
Potential Mediators from our Conceptual Model (Aim 4)
Self-Determination Theory (SDT) Constructs
  • -

    Autonomy, competence, and relatedness

  • -

    Motivational style
  • -

    Health Care Climate Questionnaire (autonomy) [53], Perceived Competence Scale [53], Intrinsic Motivation Inventory (Intrinsic motivation & relatedness) [54], Exercise Identity [55]
Social Cognitive Theory (SCT) Constructs
  • -

    Self-efficacy

  • -

    Self-control of performance and Self-regulation

  • -

    Outcome expectations
  • -

    Weight efficacy lifestyle questionnaire [56]

  • -

    Weight, diet, and activity self-monitoring

  • -

    Exercise Goal-Setting Scale and Exercise Planning and Scheduling Scale [57]

  • -

    Healthstyles Survey [58]

  • -

    Outcome expectations for exercise scale [59]
Intervention engagement
  • -

    Session adherence

  • -

    Self-monitoring and self-weighing adherence
  • -

    Coaching session completion (%)

  • -

    Number of days weight (obtained from smart scale), >1000 kcal (diet), and activity (MPA and strength training)
Knee symptoms
  • -

    Self-reported knee symptoms
  • -

    Knee injury and Osteoarthritis Outcome Score (KOOS) [60]
Dietary intake
  • -

    Energy intake (kcal/day)

  • -

    Macronutrient intake
  • -

    National Cancer Institute Automated Self-Administered (ASA) 24-h Dietary Recall [61]
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2.8. Sample size considerations

The study was originally designed to recruit 250 participants, providing 85 % power to detect a clinically meaningful difference of 5 kg weight loss from baseline to 6 months in participants with SD = 12 assuming 20 % attrition. Due to slower-than-anticipated recruitment, the final sample size was 200 participants. We will recruit 212 participants into the study expecting that no more than 20 % of these participants will fail to return at the 6-, 12-, and 18-month assessments, yielding at least 84 participants or change from baseline to 6, 12, and 18 months. To estimate power for Aim 1, we expect to detect 5.2 kg weight loss from baseline to 6 months in participants in the PACE group while only modest or no reduction in CDSM, assuming SD = 12 or smaller for both groups. With 212 participants, allowing for 20 % attrition (leaving at least 84 in each group), we have 80 % power to detect a minimum effect size of 0.51 for Aims 1–2 assuming a power of 85 % with two-sided significance level of 0.05 using a two-sample t-test.69

2.9. Statistical analyses

The primary analysis will examine changes in weight at 6 months during the PACE weight loss program relative to CDSM. Secondary analyses will examine differences in changes between PACE and the CDSM group in pain intensity (PROMIS), physical function (6-min walk test) and objectively measured physical activity (MVPA) at 6 months. We will use an intent-to-treat approach for primary analyses. Specifically, we will use multiple linear regression with weighted generalized estimating equations to account for follow-up assessment measures, controlling for potential baseline covariates (i.e., sex, age, race/ethnicity, education, comorbidities, and recruitment site). Model terms will include intervention group indicator, follow-up visit (baseline, 6 months, 12 months, 18 months), and the interaction terms between intervention group and follow-up visits (to allow differences between groups to vary over time). Additionally, analyses will examine the full treatment effect and maintenance of weight loss, physical function (6-min walk test), pain intensity (PROMIS), and physical activity (MVPA) at 12 and 18 months. Mediation analyses will be conducted to examine whether associations between PACE/CDSM groups and outcomes are mediated by the following potential behavioral and psychosocial mediators: 1) coaching calls completed; 2) adherence to self-monitoring; and 3) SDT and SCT constructs. Structural equation modeling using linear regression accounting for follow-up assessments will be employed in these analyses for each outcome. Statistical testing for each pre-specified hypothesis will use the nominal significance (alpha) level of 0.05.

The cost-effectiveness of the PACE program relative to CDSM will be conducted from a budgetary perspective. Due to the randomized controlled design of the project, our cost-effectiveness analysis is a simple difference of pre-post differences in costs and benefits between the intervention and CDSM groups. The evaluation will follow the methods to calculate incremental cost effectiveness ratios (ICER) described in Siegel et al. [62] and Drummond et al. [63] We will consider ICERs with eight primary categories of outcomes, in terms of cost per (a) body weight reduced, measured in kilograms; (b) objectively-measured physical function increased, measured in feet or seconds as needed; (c) physical activity increased, measured in minutes/week; (d) dietary intake reduced, measured in calories/day; (e) pain levels reduced, measured using the PROMIS and WOMAC scales; (f) work productivity increased; (g) healthcare utilization reduced (i.e., ED visits, medications, inpatient admission), with (h) cost per quality-adjusted life years (QALYs) increased as our main outcome of interest.

3. Discussion/Summary

This protocol paper provides a comprehensive overview of the behavioral interventions used in the Healthy Living study, which aims to evaluate the effectiveness, cost-effectiveness, and long-term sustainability of PACE, a refined patient-centered weight loss program tailored specifically for adults after TKR. If proven effective in improving both short- and long-term outcomes, and demonstrated to be cost-effective, PACE could offer a scalable, impactful approach to improve the health and wellbeing of the growing population undergoing TKR.

Data availability

No data was used for the research described in the article.

Funding

Research reported in this publication was supported by the National Institute on Aging of the National Institutes of Health under Award Number R01AG070004. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Declaration of competing interest

J.B.J. is a consultant for Vilex. All other authors declare no conflict of interest.

Handling Editor: Professor H Madry

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