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Active, Not Recruiting

NCT Number: NCT04107649

Knee Arthroplasty Activity Trial

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.

Active, Not Recruiting

This study is active but is not currently recruiting participants.

Key information

Conditions

Knee Osteoarthritis Arthritis Behavior Joint Diseases Motor Activity Musculoskeletal Diseases Osteoarthritis Osteoarthritis, Knee Rheumatic Diseases Total Knee Replacement

Age range

40 year–85 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Northwestern Memorial Hospital, Chicago, Illinois, United States

Loading trial locations.

About this study

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).

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • 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)

Exclusion criteria

  • 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
  • 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

Treatment and study plan

Telephonic Active Coaching (Motivational Interviewing) + Financial Incentives

Behavioral

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.

Other names: TAC(MI)+FI

Wrist based activity tracker wear

Behavioral

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 Activities

Other

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.

Primary outcomes

  1. 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.

Secondary outcomes

  1. Change in average daily step count

    Time frame: 2-week pre-TKR to 32-weeks post-TKR

    Change in subjects' average daily step count from pre-TKR to 32-weeks post-TKR as measured by the ActiGraph.

  2. Change in weekly minutes of moderate-to-vigorous activity (MVPA)

    Time frame: 2 week pre-TKR to 32-weeks post-TKR

    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.

  3. Change in average daily sedentary time

    Time frame: 2 weeks pre-TKR to 32-weeks post-TKR

    Change in subjects' daily sedentary time from pre-TKR to 32-weeks post-TKR as measured by the ActiGraph.

Other outcomes

  1. Durability of changes in activity levels

    Time frame: 2 weeks pre-TKR to 24 months post-TKR

    Changes in subjects' activity levels at 12-, 18-, and 24-months post-TKR as measured by the ActiGraph.

  2. Change in pain and functional status

    Time frame: 2 weeks pre-TKR to 24 months post-TKR

    Change in subjects' pain and functional status at 8-, 12-, 18-, and 24-months post-TKR as measured by the questionnaire.

  3. Change in quality of life

    Time frame: 2 weeks pre-TKR to 24 months post-TKR

    Change in subjects' quality of life at 8-, 12-, 18-, and 24-months post-TKR as measured by the questionnaire.

  4. Change in performance measures

    Time frame: 2 weeks pre-TKR to 6 months post-TKR

    Change in subjects' performance at 32 weeks post-TKR as measured by performance tests.

  5. Change in cost

    Time frame: 2 weeks pre-TKR to 24 months post-TKR

    Change in subjects' medical costs at 8-, 12-, 18-, and 24-months post-TKR as measured by the questionnaire.

Sponsors and collaborators

Lead sponsor

Brigham and Women's Hospital

Other

Collaborators

  • Northwestern Memorial Hospital
  • University at Buffalo
  • University of Kansas Medical Center
  • University of Nebraska

Registry information

Acronym: KArAT

Important dates

Study start
2023
Primary completion
2028
Study completion
2028
First posted
Sep 27, 2019
Registry last updated
Nov 24, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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