KArAT Clinical Trial

KArAT (Knee Arthroplasty Activity Trial) is a large, multi-site study testing whether one-on-one support from a health coach and small financial rewards can help people become more physically active after total knee replacement surgery.

Trial Overview

Each year, over 750,000 Americans undergo total knee replacement (TKR) to relieve pain and restore function caused by advanced osteoarthritis. While surgery is highly effective at reducing pain and improving function, studies show that up to 80% of patients do not increase their physical activity levels after recovery, missing a critical opportunity to improve long-term health outcomes, including cardiovascular fitness and weight management. To address this gap, the Arthritis Foundation and the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) are supporting the KArAT interventional trial. This innovative study will test whether personalized health coaching and financial incentives can help patients get moving — and stay moving — after TKR.

KArAT at a Glance

What type of study is the KArAT trial?

KArAT is a randomized controlled trial focused on behavior change. It tests whether personalized health coaching and small financial rewards can help people become more physically active after total knee replacement surgery, supporting recovery and long-term health.

How does the KArAT trial use health coaching to support recovery after knee replacement?

In the KArAT trial, patients may receive regular phone calls from a health coach starting about six weeks after surgery. The coach helps them set step goals, offers encouragement and talks through challenges. This support, along with activity tracking and small rewards, is designed to help patients stay active during recovery.

What happens when a patient is enrolled?

When a patient enrolls in the KArAT trial, they complete baseline surveys and wear an activity monitor for one week before knee replacement surgery. After surgery, they are randomly assigned to one of three groups: usual care, usual care with a Fitbit tracker, or usual care with a Fitbit, personalized health coaching plus financial rewards. Participants are monitored for two years through periodic surveys, activity tracking and scheduled check-in calls. Those in the coaching group receive weekly or biweekly phone sessions and can earn financial incentives for meeting physical activity goals.

Are there risks associated with the study?

The KArAT study uses low-risk interventions, including remote health coaching, wearable activity trackers and financial incentives. These components are generally safe, with only minor issues like skin irritation or mild musculoskeletal strain reported in similar studies. Participants are monitored to ensure safety throughout the trial.

For Providers:
National Clinical Trial No. for the KArAT clinical trial
NCT04107649

For more information about the KArAT trial, visit ClinicalTrials.gov.

Math and Medicine Just Adds Up for Elena Losina, PhD

This principal investigator leads several Arthritis Foundation-funded studies in preventing osteoarthritis.

Read Article

Annie Nolan Helps Trial Participants Increase Activity

Research assistant puts her interest in improving quality of life to work in the KArAt Clinical Trial.

Read Article

KArAT Trial

Rationale & Design

This manuscript outlines the rationale, study design and implementation of the KArAT trial, which is exploring incentives to increase activity after total knee arthroscopy.

Read Manuscript

Scientific Publications

KArAT Presentation

Elena Losina, PhD, lead principal investigator of the Knee Arthroplasty Activity Trial (KArAT) clinical trial and a professor of orthopedic surgery at Brigham and Women's Hospital, shares a technical overview of the KArAT trial and its progress. Check back for updates.

See the Presentation

Clinical Trial Sites

Brigham and Women's Hospital, Boston, MA
- Principal Investigator: Elena Losina, PhD, MSc
Northwestern Memorial Hospital, Chicago, IL
- Site Principal Investigator: Rowland Chang, MD, MPH
University of Kansas Medical Center, Kansas City, KS
- Site Principal Investigator: Neil Segal, MD
University of Nebraska Medical Center, Omaha, NE, and Columbus, OH
- Site Principal Investigator: Elizabeth Wellsandt, PT, DPT, PhD
University at Buffalo, Buffalo, NY
- Site Principal Investigator: Scott R. Nodzo, MD

Osteoarthritis Research Program

The Arthritis Foundation’s osteoarthritis (OA) program aims to accelerate the development of effective, evidence-based solutions to improve outcomes for people living with OA.

PIKASO Clinical Trial

PIKASO is a collaborative, randomized clinical trial testing whether metformin can slow or prevent osteoarthritis progression in people with major knee injuries.

Get the Study Details

TOPS Clinical Trial

The TOPS clinical trial tests if diet and exercise can help women over 50 reduce their risk of knee osteoarthritis.

Learn More

Stay in the Know. Live in the Yes.

Get involved with the arthritis community. Tell us a little about yourself and, based on your interests, you’ll receive emails packed with the latest information and resources to live your best life and connect with others.