Knee OsteoarthritisKArATNCT04107649
Knee Arthroplasty Activity Trial
A study testing Telephonic Active Coaching (Motivational Interviewing) + Financial Incentives, Wrist based activity tracker wear and Basic Study Activities in people with Knee Osteoarthritis and Total Knee Replacement, run by Brigham and Women's Hospital at 5 sites in United States.
Trial summary
Total knee replacement (TKR) is a common and costly procedure widely used to relieve pain and improve function in patients with symptomatic advanced knee osteoarthritis (OA). As of 2013, the annual incidence of TKR was over 680,000 surgeries and annual costs exceeded $11 billion. Read more about this study
- Who is it for?
- Ages 40 to 85 years
- Conditions the study is for
- Knee Osteoarthritis, Total Knee Replacement
- What is being tested?
- Telephonic Active Coaching (Motivational Interviewing) + Financial Incentives, Wrist based activity tracker wear and Basic Study Activities
- Type of treatment
- Lifestyle or therapy programme
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 600 participants
- Where
- 5 sitesUnited States
- Study dates
- 27 Apr 2023to 15 Jun 2028
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 40 to 85 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Age 40-85 years
- English-speaking
- Scheduled to undergo primary, unilateral total knee replacement (TKR) at one of the 4 recruitment centers
- OA is principal underlying indication for TKR
- During an accelerometer run-in period lasting one week at baseline (prior to surgery), subjects must show that they can comply with waist-worn physical activity tracker protocols by wearing the activity tracker for ≥4/7 days of the week for ≥10 hours/day
- Regular access to a personal computer, laptop, tablet, or smartphone for wrist-worn activity tracker syncing
- Satisfying average baseline steps/day criteria (calculated from waist-worn activity tracker data from the run-in period)
Who cannot join
- Non-English speaking
- Residence in nursing home
- Diagnosis of dementia, epilepsy, Parkinson's Disease, or diabetes with peripheral neuropathy
- Inflammatory arthritis (rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, reactive arthritis, systemic lupus erythematosus, polymyalgia)
- Psychological issues that preclude participation
- Inpatient or other musculoskeletal surgery scheduled within six months following index primary TKR
Show all 9Show fewer
- Uses a wheelchair to ambulate (subjects who use a cane will be eligible)
- Surgeon-documented other reason for study exclusion
- Subject does not have regular access to a device capable of receiving email or text messages
Trial locations and contacts
5 sites in 1 country.
5 sites in 1 country
United States5 sites
Brigham and Women's Hospital
Boston, Massachusetts, 02115
University at Buffalo
Buffalo, New York, 14215
Northwestern Memorial Hospital
Chicago, Illinois, 60611
University of Kansas Medical Center
Kansas City, Kansas, 66160
University of Nebraska Medical Center
Omaha, Nebraska, 68198
About this study
Total knee replacement (TKR) is a common and costly procedure widely used to relieve pain and improve function in patients with symptomatic advanced knee osteoarthritis (OA). As of 2013, the annual incidence of TKR was over 680,000 surgeries and annual costs exceeded $11 billion. Growing evidence suggests that while pain and functional status improve following TKR, physical activity (PA) typically does not surpass pre-TKR levels. Engagement in PA can meaningfully improve quality of life (QoL), pain, and function. Given the large investment in TKR, the effectiveness and cost-effectiveness of TKR could be substantially increased if TKR recipients became more physically active.
The Knee Arthroplasty Activity Trial (KArAT) is a randomized controlled trial and participants will be randomly assigned to one of three arms. Participants across all arms will receive usual post-operative care for TKR surgery. Participants in the first arm will complete basic study activities, such as responding to surveys and attending two in-person clinic visits. Participants in the second arm will do the same and also receive a wrist-based physical activity tracker intervention. Participants in the third arm will receive a telephonic active coaching (motivational interviewing) and financial incentives (for reaching physical activity goals) (TAC(MI)+FI) based intervention, as well as a wrist-based physical activity tracker intervention. The second and third arms will be eligible to receive lottery-based financial rewards for wearing a wrist-worn activity tracker for twenty-four months during the study.
Read the detailed description
The investigators have designed the KArAT trial with two specific aims. First, to conduct a parallel three-arm RCT to establish the efficacy and sustainability of the effect of personalized intervention built on the principles of behavioral science and behavioral economics in improving PA among sedentary people who have undergone TKR. Our second aim is to establish the cost-effectiveness and budget impact of TAC(MI)+FI to improve PA in persons who have undergone TKR.
The three arms will include:
Arm 1: Usual post-TKR care
Arm 2: Usual post-TKR care + Wrist-based physical activity tracker wear
Arm 3: Usual post-TKR care + Wrist-based physical activity tracker wear + Telephonic Active Coaching (Motivational Interviewing) + Financial Incentives (TAC(MI)+FI).
- Conditions
- Knee Osteoarthritis, Total Knee Replacement
- Being tested
- Telephonic Active Coaching (Motivational Interviewing) + Financial Incentives, Wrist based activity tracker wear, Basic Study Activities
- Keywords
- Physical Activity, Total Knee Replacement, Knee Osteoarthritis
- Medical subject headings
- Osteoarthritis, Knee, Motor Activity
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Telephonic Active Coaching (Motivational Interviewing) + Financial IncentivesBehavioural
Also called TAC(MI)+FI
As part of TAC(MI)+FI, participants speak with a health coach at Brigham and Women's Hospital once a week via telephone for weeks 6-13 following surgery, and once every other week for weeks 14-31 after surgery. Participants in this arm can receive financial rewards for achieving weekly physical activity goals, as well as bonus rewards for achieving goals multiple weeks in a row. Over the course of this 6-month long TAC(MI)+FI intervention period, these participants are able to receive up to $680 for meeting physical activity goals, and up to $95 in bonus rewards.
Wrist based activity tracker wearBehavioural
Activity tracking data will be collected on a weekly basis. Participants who receive this intervention are eligible to be entered into a lottery to win one of two $25 rewards for every week they wear their wrist-based activity tracker >10 hours for >4/7 days a week, beginning 6-weeks after surgery.
Basic Study ActivitiesOther
Basic study activities begin two-weeks before TKR and end approximately 24-months after TKR. Basic study activities include: two in-person visits at the local clinic site (2 weeks before TKR and 32-weeks after TKR), having check-in calls with study staff weekly from weeks 1-13 after surgery and every other week for weeks 14-31, completing 6 surveys, and wearing an ActiGraph activity tracker (waist-worn) for five one-week periods throughout the study (2-weeks before-TKR, 32-weeks post-TKR, one-year post-TKR, 18-months post-TKR, two-years post-TKR). All participants will be eligible to receive up to $235 for completing these activities over the course of two years.
| Study group | Role | What they receive |
|---|---|---|
| Arm1 | Other | Participants in this arm receive usual post-operative care and complete all basic study activities, which include: attending 2 in-clinic visits at designated time-points, having regular check-in calls with study staff over the intervention period, wearing and returning waist-worn activity trackers at 5 time points over two years, and completing 6 study surveys. Receives: Other: Basic Study Activities |
| Arm2 | Experimental | Participants in this arm receive usual post-operative care, complete all basic study activities (as described in arm 1) and receive the wrist-based activity tracker intervention. Receives: Behavioral: Wrist based activity tracker wear; Other: Basic Study Activities |
| Arm3 | Experimental | Participants in this arm receive usual post-operative care, complete all basic study activities (as described in arm 1), receive wrist-based activity tracker intervention, and receive the TAC(MI)+FI. Receives: Behavioral: Telephonic Active Coaching (Motivational Interviewing) + Financial Incentives; Behavioral: Wrist based activity tracker wear; Other: Basic Study Activities |
What is being measured
The primary outcome is the main question the study is designed to answer.
Proportion of Subjects Engaged in at least 150 min/week of moderate-to-vigorous physical activity (MVPA).
The primary outcome of this trial is the proportion of subjects who meet or surpass the PA threshold of 150 minutes per week of at least moderate physical activity, which is defined as 3 metabolic equivalents (METs), at 32-weeks post-TKR.
Measured: 32-weeks post-TKR
Secondary outcomes (3)
Change in average daily step count
Change in subjects' average daily step count from pre-TKR to 32-weeks post-TKR as measured by the ActiGraph.
Measured: 2-week pre-TKR to 32-weeks post-TKR
Change in weekly minutes of moderate-to-vigorous activity (MVPA)
Change in the number of minutes per week that subjects spend engaged in MVPA from pre-TKR to 32-weeks post-TKR as measured by the ActiGraph.
Measured: 2 week pre-TKR to 32-weeks post-TKR
Change in average daily sedentary time
Change in subjects' daily sedentary time from pre-TKR to 32-weeks post-TKR as measured by the ActiGraph.
Measured: 2 weeks pre-TKR to 32-weeks post-TKR
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted27 Sep 2019
- Study start27 Apr 2023
- Primary completion15 Jun 2028 (estimated)
- Study completion15 Jun 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (1)Papers the sponsor has linked to this study.
- Other trials for Knee OsteoarthritisStudies of the same condition, open and under way.
- More trials run by Brigham and Women's HospitalThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- Three arm parallel randomized control trial.
- Masking
- Triple blind
- Who is masked
- Care provider, Investigator, Outcomes assessor
- Enrolment
- 600 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Brigham and Women's Hospital
- Sponsor type
- University, hospital or other
- Collaborators
- Northwestern Memorial Hospital, University of Kansas Medical Center, University at Buffalo, University of Nebraska
- Responsible party
- Principal investigator, Elena Losina, Brigham and Women's Hospital
- Investigators
- Elena Losina, Ph.D., Principal investigator, Brigham and Women's Hospital
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04107649
- Sponsor's protocol ID
- 2019P002700
- Acronym
- KArAT
- Status last verified
- Nov 2025
- First submitted
- 24 Sep 2019
- Last updated
- 24 Nov 2025
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
Publications
Losina E, Collins JE, Kumara M, Ehrlich-Jones L, Opare-Addo M, Safran-Norton C, Segal NA, Mitchell LM, Kopp PT, Selzer F, Mass H, Paskewicz M, Chang RW, Dunlop D, Chen AF, Lerner S, Chin S, Pellegrini C, Katz JN. KArAT (Knee Arthroplasty Activity Trial): Rationale and design features of a multicenter randomized controlled trial. Osteoarthr Cartil Open. 2024 Aug 23;7(2):100512. doi: 10.1016/j.ocarto.2024.100512. eCollection 2025 Jun.
PubMed 40276263
Study at a glance
From the registry record, last updated by the sponsor on 24 Nov 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Knee Arthroplasty Activity Trial
- ClinicalTrials.gov ID
- NCT04107649
- Acronym / sponsor ID
- KArAT / 2019P002700
- Conditions
- Knee Osteoarthritis, Total Knee Replacement
- Keywords
- Physical Activity, Total Knee Replacement, Knee Osteoarthritis
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 600 participants (estimated)
- Lead sponsor
- Brigham and Women's HospitalUniversity, hospital or other
- Collaborators
- Northwestern Memorial Hospital, University of Kansas Medical Center, University at Buffalo, University of Nebraska
- Study start
- 27 Apr 2023 (actual)
- Primary completion
- 15 Jun 2028 (estimated)
- Study completion
- 15 Jun 2028 (estimated)
- First posted
- 27 Sep 2019 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Total knee replacement (TKR) is a common and costly procedure widely used to relieve pain and improve function in patients with symptomatic advanced knee osteoarthritis (OA). As of 2013, the annual incidence of TKR was over 680,000 surgeries and annual costs exceeded $11 billion. Growing evidence suggests that while pain and functional status improve following TKR, physical activity (PA) typically does not surpass pre-TKR levels. Engagement in PA can meaningfully improve quality of life (QoL), pain, and function. Given the large investment in TKR, the effectiveness and cost-effectiveness of TKR could be substantially increased if TKR recipients became more physically active.
The Knee Arthroplasty Activity Trial (KArAT) is a randomized controlled trial and participants will be randomly assigned to one of three arms. Participants across all arms will receive usual post-operative care for TKR surgery. Participants in the first arm will complete basic study activities, such as responding to surveys and attending two in-person clinic visits. Participants in the second arm will do the same and also receive a wrist-based physical activity tracker intervention. Participants in the third arm will receive a telephonic active coaching (motivational interviewing) and financial incentives (for reaching physical activity goals) (TAC(MI)+FI) based intervention, as well as a wrist-based physical activity tracker intervention. The second and third arms will be eligible to receive lottery-based financial rewards for wearing a wrist-worn activity tracker for twenty-four months during the study.
Detailed description
The investigators have designed the KArAT trial with two specific aims. First, to conduct a parallel three-arm RCT to establish the efficacy and sustainability of the effect of personalized intervention built on the principles of behavioral science and behavioral economics in improving PA among sedentary people who have undergone TKR. Our second aim is to establish the cost-effectiveness and budget impact of TAC(MI)+FI to improve PA in persons who have undergone TKR.
The three arms will include:
Arm 1: Usual post-TKR care
Arm 2: Usual post-TKR care + Wrist-based physical activity tracker wear
Arm 3: Usual post-TKR care + Wrist-based physical activity tracker wear + Telephonic Active Coaching (Motivational Interviewing) + Financial Incentives (TAC(MI)+FI).
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Triple blind (care provider, investigator, outcomes assessor)
- Number of arms
- 3
- Model description
- Three arm parallel randomized control trial.
| Arm | Type | Receives |
|---|---|---|
| Arm1 | Other | Other: Basic Study ActivitiesParticipants in this arm receive usual post-operative care and complete all basic study activities, which include: attending 2 in-clinic visits at designated time-points, having regular check-in calls with study staff over the intervention period, wearing and returning waist-worn activity trackers at 5 time points over two years, and completing 6 study surveys. |
| Arm2 | Experimental | Behavioral: Wrist based activity tracker wear, Other: Basic Study ActivitiesParticipants in this arm receive usual post-operative care, complete all basic study activities (as described in arm 1) and receive the wrist-based activity tracker intervention. |
| Arm3 | Experimental | Behavioral: Telephonic Active Coaching (Motivational Interviewing) + Financial Incentives, Behavioral: Wrist based activity tracker wear, Other: Basic Study ActivitiesParticipants in this arm receive usual post-operative care, complete all basic study activities (as described in arm 1), receive wrist-based activity tracker intervention, and receive the TAC(MI)+FI. |
Who may qualify
- Ages
- 40 to 85 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (7 listed)
- Age 40-85 years
- English-speaking
- Scheduled to undergo primary, unilateral total knee replacement (TKR) at one of the 4 recruitment centers
- OA is principal underlying indication for TKR
- During an accelerometer run-in period lasting one week at baseline (prior to surgery), subjects must show that they can comply with waist-worn physical activity tracker protocols by wearing the activity tracker for ≥4/7 days of the week for ≥10 hours/day
Key exclusion criteria (9 listed)
- Non-English speaking
- Residence in nursing home
- Diagnosis of dementia, epilepsy, Parkinson's Disease, or diabetes with peripheral neuropathy
- Inflammatory arthritis (rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, reactive arthritis, systemic lupus erythematosus, polymyalgia)
- Psychological issues that preclude participation
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Telephonic Active Coaching (Motivational Interviewing) + Financial IncentivesAlso: TAC(MI)+FIAs part of TAC(MI)+FI, participants speak with a health coach at Brigham and Women's Hospital once a week via telephone for weeks 6-13 following surgery, and once every other week for weeks 14-31 after surgery. Participants in this arm can receive financial rewards for achieving weekly physical activity goals, as well as bonus rewards for achieving goals multiple weeks in a row. Over the course of this 6-month long TAC(MI)+FI intervention period, these participants are able to receive up to $680 for meeting physical activity goals, and up to $95 in bonus rewards. | Behavioural | Arm3 |
| Wrist based activity tracker wearActivity tracking data will be collected on a weekly basis. Participants who receive this intervention are eligible to be entered into a lottery to win one of two $25 rewards for every week they wear their wrist-based activity tracker >10 hours for >4/7 days a week, beginning 6-weeks after surgery. | Behavioural | Arm2, Arm3 |
| Basic Study ActivitiesBasic study activities begin two-weeks before TKR and end approximately 24-months after TKR. Basic study activities include: two in-person visits at the local clinic site (2 weeks before TKR and 32-weeks after TKR), having check-in calls with study staff weekly from weeks 1-13 after surgery and every other week for weeks 14-31, completing 6 surveys, and wearing an ActiGraph activity tracker (waist-worn) for five one-week periods throughout the study (2-weeks before-TKR, 32-weeks post-TKR, one-year post-TKR, 18-months post-TKR, two-years post-TKR). All participants will be eligible to receive up to $235 for completing these activities over the course of two years. | Other | Arm1, Arm2, Arm3 |
Primary outcome
Proportion of Subjects Engaged in at least 150 min/week of moderate-to-vigorous physical activity (MVPA).
Time frame: 32-weeks post-TKR
The primary outcome of this trial is the proportion of subjects who meet or surpass the PA threshold of 150 minutes per week of at least moderate physical activity, which is defined as 3 metabolic equivalents (METs), at 32-weeks post-TKR.
3 secondary outcomes
Change in average daily step count
Time frame: 2-week pre-TKR to 32-weeks post-TKR
Change in weekly minutes of moderate-to-vigorous activity (MVPA)
Time frame: 2 week pre-TKR to 32-weeks post-TKR
Change in average daily sedentary time
Time frame: 2 weeks pre-TKR to 32-weeks post-TKR
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 24 Nov 2025.
- Derived from this study: PubMed 40276263Losina E, Collins JE, Kumara M, Ehrlich-Jones L, Opare-Addo M, Safran-Norton C, Segal NA, Mitchell LM, Kopp PT, Selzer F, Mass H, Paskewicz M, Chang RW, Dunlop D, Chen AF, Lerner S, Chin S, Pellegrini C, Katz JN. KArAT (Knee Arthroplasty Activity Trial): Rationale and design features of a multicenter randomized controlled trial. Osteoarthr Cartil Open. 2024 Aug 23;7(2):100512. doi: 10.1016/j.ocarto.2024.100512. eCollection 2025 Jun.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Elena Losina, Ph.D. principal investigator
Brigham and Women's Hospital
5 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Telephonic Active Coaching (Motivational Interviewing) + Financial Incentives, Wrist based activity tracker wear and Basic Study Activities in people with Knee Osteoarthritis and Total Knee Replacement, run by Brigham and Women's Hospital at 5 sites in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 7 inclusion and 9 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 24 Nov 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 5 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Proportion of Subjects Engaged in at least 150 min/week of moderate-to-vigorous physical activity (MVPA). (time frame: 32-weeks post-TKR). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT04107649, which also lists 1 linked publication.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 24 Nov 2025.