A consumer co-designed community physical activity program for Australians living with osteoarthritis (CASCADE-OA): A randomised controlled trial protocol

Abstract

Objective

This protocol will detail the methodology of the CASCADE-OA trial that will determine the effectiveness of an evidence-based and co-designed walking program, Walk with Ease Australia in increasing physical activity levels in people with osteoarthritis (OA).

Design

We will undertake a two-arm parallel assessor blinded RCT in a hybrid type 1 effectiveness-implementation design. 414 participants with a clinical diagnosis of knee or hip OA will be recruited across Australia through state and territory arthritis consumer advocacy groups, an OA management program in a public hospital setting, and social media. Participants with co-existing inflammatory arthritis or those already meeting physical activity guidelines will be excluded. Participants will be randomised 1:1 into either the Walk with Ease Australia + Fitbit™ group (intervention) or the Fitbit™ only group (comparator). The intervention period will be 12 weeks and participants will be followed for 12 months from randomisation. The primary outcome is average daily step count at 12 weeks as assessed by Fitbit™. Secondary outcomes include pain, disability, quality of life, self-efficacy, work absenteeism and healthcare utilisation. Implementation outcomes will be collected based on the RE-AIM framework domains and process evaluation framework for complex interventions.

Results

The trial was registered on the Australia and New Zealand Clinical Trials Registry (ACTRN12625000185460) on February 17th, 2025 and received ethics approval from the Northern Sydney Local Health District Human Research Ethics Committee (2024/ETH01898).

Conclusion

CASCADE-OA will determine whether Walk with Ease Australia will support people in the community with OA in increasing physical activity and improving symptoms.

1. Introduction

Osteoarthritis (OA) is a debilitating and costly condition that affects more than three million Australians and 500 million people worldwide [1]. Direct healthcare for OA in Australia was estimated to cost approximately $4 billion AUD for 2020–2021 [1,2], and is likely to increase markedly by the end of this decade [3]. Current guidelines recommend lifestyle management as core components of high-value OA care [4,5]. In Australia, this is managed mostly by healthcare professionals in clinic-based settings (e.g. general practitioner (GP), physiotherapists) [6]. But there are significant barriers, such as time constraints during consultations [7], cost [8], lack of access to equipment and facilities [9], and uncertainty about dosage and the frequency and type of physical activity and exercise to recommend to people with OA [10]. Addressing these barriers may require system-level changes that are slow and costly.

Walking is a low-impact, inexpensive, accessible, and safe form of physical activity for individuals with OA [11]. The US Arthritis Foundation's Walk with Ease program is a 6-week self-directed walking program designed to meet participants' goals and needs, support them to stay motivated to complete the program, manage their pain and other OA symptoms, and show them how to exercise comfortably and safely [12]. The program improved pain, stiffness, and function in people with moderate to severe pain (≥4/10 on a 10-point numerical pain rating scale), and increased physical activity levels in people with arthritis in the US [13].

While the US and Australian contexts have some similarities (ethnic heterogeneity and ageing populations) [14], there are many differences, including the ratio of urban dwellers (Aus: 71 %; US: 42 %), and healthcare costs and systems [14]. Unlike the US, Australia has a universal healthcare scheme (Medicare), with private health facilities and insurance [15]. Meaningful engagement with consumers is central to adaptation, refinement, and successful implementation of Walk with Ease in Australia. The research team conducted co-design workshops with Australians living with OA to adapt the original Walk with Ease program to the Australian context [16]. Before the newly adapted Walk with Ease Australia is promoted to the wider community, we need to test whether the program is effective in improving physical activity levels in Australians living with OA. The CASCADE-OA trial will undertake this and help identify factors for program implementation. This protocol will detail the methodology of the CASCADE-OA trial: a parallel assessor-blided randomised controlled trial (RCT) to determine the effectiveness of Walk with Ease Australia in increasing physical activity levels in people with OA. We will also evaluate the effect of the program on pain, disability, quality of life, self-efficacy, work absenteeism and healthcare utilisation, as well as its cost effectiveness compared to usual care. We hypothesise that the Walk with Ease Australia program will improve physical activity levels against the comparator group.

2. Materials and methods

This protocol is reported in accordance with the SPIRIT recommendations for reporting intervention trial protocols [17].

2.1. Trial design

We will conduct a two-arm, parallel, assessor-blinded randomised controlled trial in a hybrid type 1 effectiveness-implementation design. The primary endpoint is average daily step count at 12 weeks. We will also evaluate the acceptability, appropriateness, feasibility, and short-term sustainability of the Walk with Ease Australia program using process evaluation frameworks [18,19]. The trial has been prospectively registered with the Australia New Zealand Clinical Trials Registry (ACTRN12625000185460) on February 17th, 2025 and approved by the Northern Sydney Local Health District Human Research Ethics Committee (HREC) (2024/ETH01898). Amendments will be discussed in the monthly trial management committee (TMC) meetings and submitted for approval to the relevant HREC. Changes will be updated to the funding body through submission of annual reports.

2.2. Trial setting

This study will be conducted in the community. The intervention will be delivered remotely, and data collection will be completed online.

2.3. Study population

Eligible participants must be:

• •Aged 45 years or older,
• •Have activity-related hip or knee joint pain of 3 or more on the 11-point numerical rating scale (NRS, 0–10),
• •Have either no morning joint-related stiffness or morning stiffness that lasts no longer than 30 min,
• •Be able to walk for at least 10 min at any pace/intensity (aided or unaided),
• •Have access to a GPS-tracking smartphone,
• •Have internet access, and
• •Be considered safe to participate in a walking trial based on the Adult Pre-Screening Screening System (APSS).

People will be ineligible if they have self-reported co-existing inflammatory arthritis (e.g. rheumatoid arthritis or gout) or self-reported to be already meeting physical activity guidelines of at least 150 min of moderate physical activity or 75 min of vigorous physical activity per week. If people experience morning-related joint stiffness >30 min and have not been formally diagnosed with inflammatory arthritis, they will be asked to clarify the duration of stiffness and whether statements related to OA symptoms apply to them. The study doctor will review the responses and confirm eligibility.

2.4. Trial procedures

Trial procedures are outlined in Fig. 1. Potential participants will be screened and provide written consent prior to participating. Once consented, they will be enrolled into the study and will be asked to wear the study-provided wrist-worn Fitbit Inspire 3™ (Fitbit Inc, San Francisco, CA, USA) for 28 days and complete baseline surveys. They will then be randomised to either the Walk with Ease Australia + Fitbit™ or Fitbit™ only groups. After six weeks, participants will be asked to complete a mid-intervention survey (T₁). Following the 12-week intervention, participants will be asked to complete the post-intervention survey (T₂), which is the primary time-point. Participants will also be asked to complete 26- and 52-week follow-up surveys (T₃ and T₄, respectively).

Fig. 1.

Trial procedures for the Walk with Ease Australia two-arm, parallel, single-blided RCT.

2.5. Recruitment

People with OA will be recruited across Australia. The primary recruitment method will be through the community: by emails from state/territory-based arthritis consumer groups to their members, social media, and emails to the OA Research Participant Network managed by the Osteoarthritis Clinical Research Group, University of Sydney. Participants from the Osteoarthritis Chronic Care Program (OACCP) at Royal North Shore and Ryde Hospitals in Sydney will also be invited to participate.

2.6. Randomisation and bliding

Eligible and consenting participants will undergo a 28-day baseline data collection period. Participants who successfully complete baseline data collection will be allocated in a 1:1 ratio to the Walk with Ease Australia + Fitbit™ or Fitbit™ only group by computer-generated random numbers using the Research Electronic Data Capture (REDCap) randomisation module, developed by an independent researcher. We will use block randomisation (permuted block design), using a block size of four stratified by index joint site (hip/knee) and biological sex. An independent statistician will generate the randomisation sequences.

The statistician will be blinded to group allocation and will be unblinded only when statistical analyses are completed. Participants and clinical trial operations staff will not be blinded to study outcomes and groups. Participants will be informed in their Participant Information Sheet and Consent Form that there are two groups in this study and that they will be randomly allocated to one group, with one group receiving a Fitbit™ and a “guided walking program”, and the other receiving a Fitbit™ only.

2.7. Baseline demographics

Demographic, descriptive and medical information will be collected from all participants at baseline, and will include:

• •Age, date of birth, biological sex, height and weight, ethnicity, level of education, employment status, main occupation, and residential postcode.
• •Medical history/clinical characteristics, including history of hip or knee pain, presence of OA in other joints, past history of treatments for hip or knee pain.
• •Comorbidities using a modified Katz co-morbidity questionnaire [20].
• •Perceived neighbourhood environment, where participants will be asked about their perceptions of different aspects of their neighbourhood environment including access to public transport and fresh food, as well as safety as a result of traffic and crime [21].

2.8. Intervention (Walk with Ease Australia + Fitbit™)

The intervention will be the self-directed 12-week Walk with Ease Australia program [16].

This has been adapted from a 6-week self-directed walking program developed by the Thurston Arthritis Research Centre and the Institute on Aging of the University of North Carolina, for use in the USA. As the Walk with Ease Australia program will be self-directed and participants will choose their own walking goals, they can modify the intervention according to their circumstances and goals. Each week, participants will be prompted to read chapters from the Walk with Ease workbook to equip them with the tools and knowledge to achieve their walking goals including: initial, midway, and end-point self-assessments, a guide to setting up a walking plan, a 5-step guide on what should be included in a walking session (warm-up, gentle stretching, walking, and speed up, cool down, and gentle stretching), the frequency, intensity, time (duration), and type of training (FITT) principles (40), and a walking diary (“Companion Workbook”). Table 1 outlines the week-by-week activities that participants can follow. In the introductory chapter of the book, it is outlined that participants should “work up to walking at least three time a week”. We will define adherence to the program as walking three times per week for at least nine of the 12 weeks during the intervention period.

Table 1.

Week-by-week activities outlined in the Walk with Ease Australia book.

Week	Chapter	What you need to do
1	Introducing walking and arthritis	•Read chapter 1 •Complete starting point self test •Start walking! •Record your walking in the companion workbook
2	Basic facts about osteoarthritis, rheumatoid arthritis and fibromyalgia	•Read chapter 2 •Try walking a bit more •Record your walking and how you felt in the companion workbook
3	Exercising with arthritis	•Read chapter 3 •Understand what moderate to vigorous physical activity feels like for you (talk test/measuring heart rate) •Try walking faster •Record your walking and how you felt in the companion workbook
4	Principles of exercise	•Read chapter 4 •Complete the FITT-VP activity •Record your walking and how you felt in the companion workbook
5	Develop your walking plan	•Read chapter 5 •Try the 5-step walking pattern activity •Record your walking and how you felt in the companion workbook
6	Extra things to consider when walking	•Read chapter 6 •Identify and record your goals for the week •Record your walking and how you felt in the companion workbook
7	Choosing a good place to walk	•Read chapter 7 •Identify a new place to walk •Record your walking and how you felt in the companion workbook
8	Anticipating and overcoming barriers	•Read chapter 8 •Try the 3-step problem solving strategy •Record your walking and how you felt in the companion workbook
9	How to maintain your walking	•Read chapter 9 •Identify some strategies to maintain your walking long-term •Record your walking and how you felt in the companion workbook
10	Health living with arthritis	•Read chapter 10 •Record your walking and how you felt in the companion workbook
11	Building a social network	•Read chapter 11 •Walk with a friend/family member •Record your walking and how you felt in the companion workbook
12	Walk with Ease Australia directory and resources	•Read chapter 12 •Record your walking and how you felt in the companion workbook

Participants in the intervention group will also receive “blinded” wrist-worn Fitbits™ (described in detail below) to monitor physical activity levels and be invited to join the private Walk with Ease Australia Facebook group.

2.9. Comparator (Fitbit only)

Participants allocated to the comparator Fitbit™ only group will receive the “blinded” Fitbit™. This is so that we can evaluate the true effect of the Walk with Ease Australia intervention, considering the interventional effect that the Fitbit™ may have on step count (primary outcome measure). The “blinded” Fitbits™ will have all goal-related display, notifications and prompts to move turned off. Step count will also not be visible on their home screen. Access to step count through the Fitbit™ mobile app cannot be disabled so it is possible that participants will see their step count if they access the app. Participants in this group will be told that we are monitoring their physical activity and to continue their activities as they normally would. Both groups will be able to access care as usual. Participants in both groups are also free to contact the study coordinator at any time should they wish to withdraw from the study. Following the end of the trial, participants will be provided free access to the Walk with Ease Australia program.

2.10. Outcomes

2.10.1. Primary outcomes

The primary outcome measure of physical activity levels will be average daily step count using Fitbit™ activity trackers. We will collect 28 days of step count data at baseline (Fig. 1). Following the subsequent data collection time points, we will collect and calculate an average step count over 14 days (Fig. 1). Fitbit™ has moderate reliability and validity compared to research-grade activity trackers to measure physical activity levels [22]. We extended the data collection range to 14 days to capture variations in activities over weekdays and two weekends, which may arise due to occupational, social, or family commitments. All step count data for each participant will be checked prior to analysis. Missing data or outlier data points will be omitted from the step count average and step count will be only averaged over the number of valid days (defined as wearing the monitor for at least seven of 14 days). The threshold for missing or outlier step counts will be calculated by Q1 (quartile 1) – 1.5 x IQR (interquartile range) for each participant. Any step counts below this value will be omitted in the overall step count calculations. A custom third-party web-based dashboard that integrates all participant Fitbit™ data was developed by Vulsen Health (https://vulsen.com/) to enable the research team to monitor and collect physical activity levels.

2.10.2. Secondary outcomes

We will collect outcomes related to OA symptoms, self-efficacy, health-related quality of life, absenteeism/presenteeism and healthcare utilisation and medication use at all time points using validated tools if available [[23], [24], [25], [26], [27]] and customised questionnaires (Table 2). The data will be collected through online surveys at all time points (Fig. 1).

Table 2.

Secondary outcomes and instruments.

Outcome	Instruments	Description of instrument
Pain	Pain intensity using NRS (0–10) [23]	Participants will be asked to rate their average pain over the previous week on a scale of 0–10, where 0 represents no pain and 10 indicates the worst pain imaginable.
Disability	Physical function subscale of knee osteoarthritis outcome score (KOOS) or the hip osteoarthritis outcome score (HOOS) [24]	Participants will be asked to rate how much the symptoms in their study joint affected them in a 5-point likert scale (none, mild, moderate, severe and extreme) [24].
Self-efficacy	Arthritis Self-Efficacy Pain Subscale [25]	Five-item questionnaire, asking how certain participants feel about managing their arthritis pain from 1 (very uncertain) to 10 (very certain) [25].
Health-related quality of life	EQ 5D 5 L [26]	A health-related multi-attribute utility quality of life instrument with five dimensions: Mobility, self-care, usual activities, pain/discomfort and anxiety/depression. Each dimension has five response levels corresponding to no problems, slight problems, moderate problems, severe problems, unable to/extreme problems [26].
Absenteeism and presenteeism at work	Health and work performance questionnaire short form [27]	The HPQ short form measures hours of work lost (absenteeism) and work performance (presenteeism). It includes 7 items asking hours of work, experience at work and job performance [27].
Healthcare utilisation and medication use	Custom questionnaire	Participants will be asked if they sought care from a health professional about their hip/knee pain. They will also be asked whether they took medication to manage their pain or other health conditions over the last four weeks. Participants will also be asked if they purchased any shoes, walking poles, knee supports and/or taping in the last four weeks for their physical activity or health.

2.11. Implementation outcomes

We will collect implementation outcomes over the 12-month data collection period (Table 3) as guided by the RE-AIM framework domains [28] and the process evaluation framework for complex interventions [19]. We will evaluate whether the program is perceived to be acceptable and appropriate for Australians with OA, and feasible to complete. We will record if people continue to use the program beyond the intervention period (sustainability) and whether they would recommend the program to others. We will use validated questionnaires to collect quantitative data such as the Acceptability of Intervention Measure (AIM), Intervention Appropriateness Measure (IAM) and the Feasibility of Intervention Measure (FIM) [29] and custom-designed surveys. The interpretation of the quantitative data will be enhanced through the collection of qualitative data through focus groups and/or semi-structured interviews from a minimum sample size of 20 participants.

Table 3.

Implementation outcome measures and assessment indicators for Type 1 hybrid effectiveness-implementation trial using the Process Evaluation Framework for Complex Interventions [19] and the RE-AIM framework [28].

Domain	Process Measures	Planning Questions	Assessment indicators
Reach	1.Percentage of people excluded (and their characteristics) 2.Percentage of people who participated out of the people who were considered eligible 3.Characteristics of participants compared to non-participants Additional process measures using the Process Evaluation Framework for Complex Interventions – Study Population component [19] 1.Recruitment and selection rate 2.Barriers and facilitators in recruitment and selection process 3.Follow up: Attrition rate 4.Barriers and facilitators for follow-up	Who are we reaching to participate in this study? What are the characteristics of people signing up to participate in this study? What made people want to sign up to this study? (Facilitators) How many people are consenting to participate in the study? What is the attrition rate at the primary timepoint (12 weeks)? What were the barriers and facilitators for people to complete follow-up measures?	•Demographic data of participants at baseline • Survey data at baseline: ○ Are participants currently receiving care for their OA or have received care? ○ Have participants been involved in clinicals trials before? •Recruitment rate •Recruitment rate using different strategies (social media, participant networks, Arthritis state groups, OACCP) •Attrition rate •Completion of data •Qualitative data from participants to determine motivations to participate •Review of field notes
Effectiveness	1.Measure of primary outcome with comparison to recommended daily step count for people with OA 2.Measure of broader outcomes 3.Measure of robustness across subgroups through moderation analyses 4.Measure of short-term attrition (%) and differential rates by participant characteristics or treatment condition Additional process measures using the Process Evaluation Framework for Complex Interventions – Multiple and Evaluation of Data components [19] 1.Quality and delivery of the interventional components 2.Barriers and facilitators for delivery of interventional components 3.Adherence to interventional components 4.Barriers and facilitators for adherence for interventional components 5.Experience of participants and instructors with interventional components 6.Outcome measures: coverage of interventional components 7.Completeness of data collection 8.Barriers and facilitators for data collection	Were physical activity levels the appropriate outcome measure to determine the effectiveness of the walk with ease Australia program? Was Fitbit™ an appropriate method to collect physical activity data? What were the participants' experiences with setting up and using Fitbit™? What were the participants' perceived benefits of the walk with ease Australia program? Was this consistent with what was seen in the Fitbit™ data? Were participants satisfied with the three components of the walk with ease Australia program: Walk with ease Australia book, walk with ease Australia companion workbook, and the Facebook group? Was there anything that was not satisfactory? Did participants in the intervention group engage with all components of the walk with ease Australia program? What were the motivators or barriers to engaging with the components of the program? Did the components of the walk with ease Australia program help people to increase their physical activity? If so, how? If not, how can they be modified to encourage improvements in physical activity? Was the walk with ease Australia program suitable for Australians with OA? Why was the program suitable/unsuitable? Was the walk with ease Australia program feasible to complete for people with OA? Why was the program feasible/unfeasible to complete? Was there a particular component that was/was not easy to do? How much did people engage with the walk with ease Australia Facebook group? How often did people engage with the group? Did the Facebook group encourage them to walk or increase their physical activity? Did the walk with ease Australia program encourage people to walk with others?	• Survey data following intervention period: ○ Satisfaction with the walk with ease Australia program and its components ○ Did the walk with ease Australia program and its components help increase participants' physical activity levels? (Feasibility) ○ Feasibility of completing the walk with ease Australia program and its components •Acceptability of intervention measure •Intervention Appropriateness measure •Feasibility of intervention measure •Qualitative data from participants on their experiences in the trial, with the intervention and its components
Adoption	Setting level 1.Characteristics of participants in both intervention and comparator groups across different settings 2.Qualitative data to understand how the walk with ease Australia program can be adopted so that it can be delivered through the arthritis state groups and OACCP. Staff level 1.Qualitative data to understand staff participation in advertising study.	How did participants differ across the settings? Were there any demographics that could explain differences in recruitment and retention of participants? How can the walk with ease Australia program be delivered through the arthritis state groups and the OACCP? What support and resources do these groups need to successfully roll out the program? Were staff at the arthritis state groups and the OACCP willing to advertise the study? What were barriers and facilitators to advertising the study? What would increase willingness to advertise the study?	•Demographic data of participants across settings •Qualitative data from arthritis state groups and OACCP on whether staff were willing to advertise the study to their consumers and patients, whether the walk with ease Australia program can be disseminated through their organisations, and what support they would need to successfully deliver walk with ease Australia program.
Implementation	1.Adaptations made to intervention during study 2.Cost of intervention (time or money) 3.Consistency of implementation – arthritis state groups, OACCP, community	Is the walk with ease Australia cost-effective compared to usual care when considering the cost of purchasing program, any equipment to complete the walking, medications, and healthcare utilisation? How did the arthritis state groups advertise the study? How did the OACCP advertise the study? What kind of people were recommended to participate in the study from each organisation? How much did the participants adhere to the walk with ease Australia program? Did participants select their own goals? How did they feel about self-selected goals? Did participants use all components of the walk with ease Australia program – the book, companion workbook and the Facebook group? How much will participants be willing to pay for the walk with ease Australia program – including access to the private Facebook group? What costs will be needed to continue the walk with ease Australia program? Considerations: Printing, binding, monitoring of Facebook group.	•Cost-effectiveness analysis of the intervention using quality of life data •Survey data on whether participants completed all aspects of the walk with ease Australia program •Survey data on healthcare and medication use, and additional equipment purchased •Qualitative data from participants on their experiences at recruitment, selecting and following their own physical activity goals, and their thoughts on the cost of the program •Qualitative data from arthritis state groups and OACCP on how the intervention was advertised and what kind of people were registering for the study.
Maintenance	Individual level 1.Measure of primary outcome (with or without comparison to a public health goal) at ≥6 month follow-up after final intervention contact 2.Measure of broader outcomes or use of multiple criteria at follow-up (e.g. quality of life or potential negative outcome) 3.Robustness data – subgroup effects over the long-term 4.Measure of long-term attrition (%) and differential rates by patient characteristics or treatment condition 5.Long-term effects using qualitative methods Setting level 1.If program is still on-going at ≥6-month post-study funding 2.If and how program was adapted long-term (which elements retained AFTER program completed) 3.Alignment to organisation mission or sustainability of business model 4.Understand setting level institutionalisation using qualitative methods	Individual level Did participants continue to use the walk with ease Australia program? Were there any barriers or facilitators to continue the program? Were there any resources that could have helped participants to continue to use or even progress in the program? Were participants encouraged to form walking groups as a result of the walk with ease Australia program? Did forming groups/Facebook group motivate participants to stay in the study? Did walk with ease Australia program have any impact on other outcomes at 26- and 52-week follow up? These outcomes include pain, self-efficacy, function, quality of life, work performance, healthcare and medication use. Setting level Would the arthritis state groups be willing to deliver the walk with Australia program in the future in the form of walking groups? What resources would they need to deliver the program? Do their staff require training? What costs would be involved to deliver the program through the arthritis state groups? Would the OACCP coordinators be willing to recommend their patients to the walk with ease Australia program in the future? What resources would they need to do this?	•Participants' step count data (physical activity) at 26- and 52-weeks in both intervention and comparator groups •Survey data at 26- and 52-weeks on sustained use of the walk with ease Australia program, including questions about how often participants walked with others. •Survey data at 26- and 52-weeks on self-reported pain, self-efficacy, function, quality of life, work performance and healthcare and medication use. •Qualitative data from participants on what would help them to continue and progress through the walk with ease Australia program. •Qualitative data from arthritis state groups and OACCP on what resources would they need to continue advertising the program (including training staff).

2.12. Retention and completion of data

The trial coordinator will regularly review the data for completeness and correctness. Participants will be sent an email via REDCap to complete study surveys at each assessment timepoint. Participants who have not completed the survey after three days will be sent a reminder via SMS. Participants will be sent a maximum of three reminders at Days 3, 5 and 7. After seven days, the study coordinator may contact the participant via phone regarding key measures and time points.

2.13. Data management

Data from questionnaires will be stored in the CASCADE-OA REDCap database hosted at the University of Sydney. REDCap is a secure, web-based application designed to support data capture for research studies. Fitbit™ data from all participants will be captured on the custom web-based database and will be stored on a secure cloud server. Data transit between the databases and the cloud server will be encrypted using industry-standard protocols. All participant data collected will be re-identifiable (i.e. coded). Only non-identifiable data will be presented in the dissemination of results. De-identified data of consented participants may be used for ancillary studies.

2.14. Sample size

A previous trial that tested a 12-week physical activity program compared to usual care in people in the community with severe knee OA demonstrated a large effect on daily step count [30]. To remain conservative, we anticipate that we will need to randomise 207 participants per group to achieve 80 % power and a moderate effect size of 0.30, accounting for 20 % dropout [31]. A total of 414 participants will need to be randomised.

2.15. Statistical analysis

A detailed statistical analysis plan will made publicly available prior to analysis. Primary and secondary outcome measures will be analysed using intention-to treat principle.

The primary outcome of step count will be analysed using a linear mixed-effects model with fixed effects for time, month, and their interaction, adjusting for baseline step count. Correlations due to recruitment setting (state and source: community or OACCP) and repeated measures will be modelled using recruitment setting and participant ID as random effects in the mixed effect model specification. Within-group changes and between-group differences will be presented as least-squares means with 95 % CIs. Other continuous outcomes will be analysed similarly using linear mixed-effects models.

For primary and other continuous outcomes, missing data will be handled indirectly through linear mixed-effects model under the missing-at-random (MAR) assumption. Robustness to deviations from MAR will be assessed using a conservative baseline observation carried forward (BOCF) imputation. Binary and count based outcomes will be analysed using generalized mixed effect models with appropriate link functions: logistic for binary and Poisson for count outcomes. All the statistical analysis will be conducted at 0.05 level of significance. The analysis will be performed in R, version 4.5.1 or STATA, version 19.0.

To evaluate the cost-effectiveness of the intervention, the incremental cost-effectiveness ratio (ICER) will be calculated from the incremental cost of the program and the change in quality of life (EQ-5D-5L). To determine cost-effectiveness, we will compare the Walk with Ease ICER with ICERs of usual care in the clinic. Sensitivity analyses will confirm the program's cost-effectiveness in different conditions (e.g. comparing baseline inactive/sedentary people with baseline moderately active people; urban vs rural/regional settings).

2.16. Data monitoring and auditing

The TMC will oversee the conduct of the trial and monitor the data. Its responsibilities include protocol development, study planning, monitoring progress, review of information from related research and implementation of recommendations from other study committees and external bodies (e.g. HREC). The trial may by audited by the HREC and/or trial sponsor.

2.17. Safety reporting

Participants will be asked to report the occurrence of any of the following safety events of interest: fall, stroke, chest pain, any injuries that result from the intervention, an OA flare, hospitalisation (excluding elective surgeries), and death. Safety event data will be collected at the 6-, 12-, 26- and 52-week timepoints via REDCap surveys. All reported safety events of interest will be reviewed by the study doctor within 48 h of the study team becoming aware of the event to assess whether the event meets the definition of a Serious Adverse Event and whether it is related to the study intervention. Contact details for research team members will be provided to participants on the Participant Information Sheet and in study communications.

3. Discussion

The Walk with Ease Australia program is a walking program co-designed with and adapted for Australians living with OA. It is community-based: people with hip or knee OA can access an evidence-based program without having to seek care from primary health professionals. It will support people with OA to self-manage their condition. The hybrid type 1 effectiveness-implementation design will enable reporting on both effectiveness and implementation outcomes. It will determine whether the program is effective on increasing physical activity levels in people in the community with OA, as well as reducing symptom severity and improving quality of life. The results will also determine whether the Walk with Ease Australia program is more cost effective than usual care. The findings will help prepare for determining implementation strategies that can be tested to enable scale-up and sustainability.

At the end of the trial period, the investigator team will develop a plan for sustainability and wider implementation of the Walk with Ease Australia program, which may include testing the program in a hybrid type 3 effectiveness-implementation design. Results from the implementation outcomes will provide key information on the reach, adoption and feasibility of the program. Using this information, we will work with key stakeholders including consumers, arthritis consumer groups and local governments to ensure that Walk with Ease Australia is available for all Australians living with OA.

Version and date

Version 1.3, 23^rd December 2025.

Trial registration

The trial protocol including the statistical analysis plan was prospectively registered with the Australia New Zealand Clinical Trials Registry (ACTRN12625000185460; https://anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=12625000185460) on 17^th February 2025.

Data sharing

De-identified individual participant data sharing will be available once major findings from the study have been published. Statistical codes will not be made publicly available.

Role of trial sponsor

The trial sponsor is the University of Sydney. The sponsor is responsible for distributing funds and ensuring that the researchers are conducting the study ethically and safely.

Roles and responsibilities

This project is led by Dr Vicky Duong and Dr Sarah Kobayashi, overseen by Prof David J Hunter. The internal trial management committee (TMC) (DJH, SK, VD, FD, ES, JPE, KB and SY) oversee the conduct of the trial, including protocol development, study planning, monitoring progress, review of information from related research and implementation of recommendations from other study committees and external bodies. The international TMC includes all chief investigators for the project (listed as authors) and are responsible for overseeing and contributing to protocol development, and evaluation and interpretation of findings.

Dissemination policy

The results of this project will be shared with the wider scientific community through journal publications, and conference presentations in accordance with the publication plan. Our results will also be disseminated through social, radio and print media, including through the Joint Action podcast hosted by Prof David Hunter and through the consumer advocacy groups.

Role of funders

This project is funded by the NHMRC Australia under the MRFF Effective Treatments and Therapies scheme (Application ID: 2023131) and the Ramsay Research and Teaching Fund. The funders are responsible for ensuring that the researchers are conducting the study with integrity.

Declaration of interests

This project is funded by the NHMRC under the MRFF Effective Treatments and Therapies scheme (Application ID: 2023131) and the Ramsay Research and Teaching Fund.

Professor Hunter is employed by the University of Sydney and Royal North Shore Hospital. His salary support for the University of Sydney is provided by Arthritis Australia and an NHMRC Investigator Grant Leadership 2 (#1194737). In addition, Prof Hunter is the editor of the osteoarthritis section for UpToDate, co-Editor in Chief of Osteoarthritis and Cartilage and board member of Osteoarthritis Research Society International. Prof Hunter provides consulting advice on scientific advisory boards for Pfizer, Lilly, TLCBio, Novartis, Tissuegene, and Biobone.

Dr Duong is supported by philanthropic funding from the Lenity Foundation. Dr Eyles is supported by a National Health and Medical Research Council Investigator Grant (#2025504).

Professor Kim Bennell receives royalties from Wolter Kluwers and her institution (Uni of Melbourne) receives grants from NHMRC, MRFF and Medibank and royalties from FutureLearn.

Professor Rana S Hinman's salary is supported by a National Health & Medical Research Council Investigator Grant (#2025733) and her institution receives grants from MRFF and Medibank and royalties from FutureLearn.

Professor Callahan is supported by funding from the National Institutes of Health and the Centers for Disease Control and Prevention.

Associate Professor Dawn Aitken receives funding from NHMRC and MRFF. She is also a Board Member for Arthritis & Osteoporosis Tasmania.

Professor Emmanuel Stamatakis is NHMRC Investigator Grant Leadership 2 (#1194510). He is a paid consultant and holds equity in Complement 1, a US-based company whose services relate to physical activity.

Handling Editor: Professor H Madry