Lifespan Orthopedics Institute
The Most Comprehensive Orthopedic Care in the Region

Bridge-Enhanced ACL Repair (BEAR)

Torn ACL? BEAR-MOON Wants You!

BEAR-MOON? What is it? And what does it have to do with my (ouch) torn ACL (anterior cruciate ligament)? 

BEAR-MOON is an acronym for BEAR (Bridge-Enhanced ACL Restoration) MOON (Multicenter Orthopaedic Outcomes Network). It’s a multi-center, randomized, clinical trial seeking adult participants with a torn ACL that has occurred within the past 50 days, who qualify for surgery

The Lifespan Orthopedics Institute is managing the only New England site, one of six across the nation, to conduct the trial with our partner physicians at University Orthopedics. This research study is approved by the FDA and funded by grants from the National Institutes of Health and the National Institute of Arthritis and Musculoskeletal and Skin Diseases.

Adult stretching while running

Join the Trial

Do you have a torn ACL? Don’t wait. Schedule an appointment with a BEAR-MOON trial physician and find out if you qualify for the trial.


Phone: 1-401-649-1906.

Injury must have occurred within the last 50 days.

The Most Common Knee Injuries Are Anterior Cruciate Ligament (ACL) Injuries 

ACL injuries are among the most common knee injuries and affect around 400,000 Americans each year. The typical treatment for this injury is reconstructive surgery. Because ACLs do not repair themselves, the surgeon typically uses a tendon graft from another part of the patient’s body to replace the ACL. In this procedure, the torn ACL fibers are completely removed and replaced with the graft, which is inserted arthroscopically into large tunnels drilled into the knee. Recovery will take months, and re-tearing is common in active individuals. 

BEAR Technology

In the BEAR procedure, the torn ACL fibers are instead sutured and stitched within the center of the knee with a device that absorbs the patient’s own blood and bridges the gap between the torn ends. This provides a healing environment for the torn ACL fibers to repair themselves together, thereby eliminating the need to harvest any tissue for a graft. The BEAR procedure is a new and different way of thinking about the surgical approach to treating ACL injuries.


The BEAR-MOON trial addresses the question of whether this new and less invasive surgical procedure can provide non-inferior outcomes to the gold standard of treatment in terms of knee laxity, a common test to evaluate the integrity of the ACL, and patient-reported outcomes.

How Are Participants Selected for This Research Study?

The BEAR-MOON trial is enrolling 200 English-speaking individuals nationwide who:

  • Are between the ages of 18 and 55
  • Have suffered a complete ACL tear (as documented on an MRI scan by a medical professional) within the past 50 days
  • Were advised by a medical professional that surgery is recommended to treat the ACL tear
  • Are willing to follow the study instructions for return visits and rehabilitation exercises

Meet the Experts

Our team of board-certified orthopedic sports medicine surgeons and researchers specializes in arthroscopic repair of sports-related injuries including complex knee reconstructions.

Brett D. Owens, MD Headshot

Brett D. Owens, MD

Division Chief, Sports Medicine, Rhode Island Hospital and The Miriam Hospital

Paul Fadale, MD Headshot

Paul Fadale, MD

Orthopedic Surgeon

Michael J. Hulstyn, MD Headshot

Michael J. Hulstyn, MD

Sports Medicine Surgeon

Braden C. Fleming, PhD Headshot

Braden C. Fleming, PhD

Director, Center of Biomedical Research Excellence (COBRE) in Skeletal Health and Repair


Your Questions Answered

The experts explain how BEAR technology works and answer the most common questions about ACL injury and repair.

As a board-certified orthopedic sports medicine surgeon, specializing in arthroscopic repair of sports-related injuries, explain how BEAR technology treatment is transforming traditional ACL treatment? (Answered by Brett D. Owens, MD)

Dr. Owens: During the course of my career, we have seen some small incremental changes to the surgical techniques in ACL reconstruction. However, the BEAR technology has the potential to transform the way we treat ACL injuries, with restoration of the native ligament and without the need to harvest a graft from another part of the knee. This change to our approach will greatly benefit our patients.

How common are ACL injuries among non-professional athletes and does age have any impact on the type of surgery provided? (Answered by Paul Fadale, MD)

Dr. Fadale: ACL tears are among the most common knee injuries. Most of these injuries happen to non-professional athletes. Commonly, they occur in a non-contact fashion with an acute twisting of the knee. ACL tears can occur at any age and are more frequent in women than men. Surgery can be tailored accordingly.

Does gender play a role in ACL injuries? (Answered by Michael J. Hulstyn, MD)

Dr. Hulstyn: Female athletes are at 2-8 times greater risk of primary ACL injury compared with males, even when controlling for sport and competition level. This difference in injury risk is an important focus of research and has been attributed to anatomy, hormonal effects, neuromuscular control, biomechanics, and sport participation.

How has new treatment for ACL injuries improved over recent decades? (Answered by Braden Fleming, PhD)

Dr. Fleming: ACL reconstruction surgery in active patients has been the gold standard treatment for more than three decades. Despite minor improvements to the procedure, clinical outcomes have not really changed. Thus, there remains a need to find a new method that is less invasive and has the potential to provide better outcomes. The BEAR procedure is a promising technique that will likely meet these goals. 

BEAR: From Discovery to Now

In the late 1990s, Martha Murray, MD, then an orthopedic surgeon with Boston Children’s Hospital, was researching why the ACL failed to heal on its own. Her discoveries led to the conceptualization of an implant that could be placed between the torn ends of the ACL to bridge the gap, which is then mixed with the patient’s own blood to stimulate healing. This concept led to the development of the Bridge-Enhanced ACL Restoration (BEAR) Implant, a fundamental change in the approach to treating ACL injuries.

This less invasive procedure lends itself to faster recovery of muscle strength after surgery and prevents morbidities associated with traditional grafts, such as kneeling pain or hamstring deficits.

Promising Trial Results

Between 2006-2012, doctors and researchers with Rhode Island Hospital, Brown University, and Boston Children’s, collaborated for a series of preclinical studies that were performed to optimize the implant, to demonstrate the safety of its use in the body, and to show that it stimulated the ACL to heal. These preclinical studies were critical for obtaining FDA approval in 2014 for the first-in-human study (“BEAR I”), which was initiated February 2015.

The primary objective of the BEAR I trial was to show that there would be no major complications (i.e., inflammation, infection, or rejection) in patients who received the implant. When the trial showed that no major complications occurred, the FDA granted approval for a second study (“BEAR II”) comparing outcomes of patients receiving BEAR to those receiving ACL reconstruction graft (“the gold standard”). Recruitment for the BEAR II trial was initiated in May 2015, and enrollment was completed June 2016.

FDA Approval Leads to BEAR-MOON

Two years after surgery, the outcomes of the two procedures proved to be similar in young and active patients, though the BEAR patients had better hamstring muscle strength. These results were key to receiving FDA clearance for the BEAR implant in December of 2020.

Given the promising results of the BEAR procedure in the BEAR I and BEAR II trials, two additional studies were approved by the FDA – the “BEAR III” trial and the “BEAR-MOON” trial. The BEAR III trial was designed to evaluate the effects of age on outcomes following the BEAR procedure. These patients are currently being followed to determine long term outcomes.

Rhode Island Hospital is one of six U.S. hospitals conducting the BEAR-MOON trial that compares outcomes of patients receiving the BEAR implant to those receiving ACL reconstruction. Recruitment for the BEAR MOON trial was initiated in September of 2021 and the study is currently underway. 

For More Information

To learn more about the BEAR-MOON trial or to schedule an appointment with a trial physician, email or call 1-401-649-1906

More information about this clinical trial and the BEAR ACL restoration procedure is available at