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Anterior Cruciate Ligament (ACL) Tears

Female ACL Tears

One-in-ten, college-age females will damage their knee ligaments sometime during their four-year NCAA career. Due to these staggering statistics, we have been actively researching methods to decrease injury rates in female athletes. My research can be grouped into the following areas.

The Hormone Relaxin

We have identified a hormone, relaxin, in some women that appears to make them more at risk for ligament injury. Relaxin works to decrease the strength of ligaments, which can be a good thing during childbirth when the pelvis needs to widen to accommodate a baby, but It’s not great when there’s no baby on the way and other important ligaments, such as the ACL, are weakened. Our research has confirmed the presence of relaxin receptors on the Anterior Cruciate Ligament (ACL) and showed that relaxin activates those receptors. Additionally, intercollegiate female athletes who sustained an ACL tear also had higher levels of relaxin in their blood, which appeared to increase their risk for ligament rupture.

More recently, we have identified that some formulations of oral contraceptive pills (OCPs) may decrease the effects of relaxin, but further clinical trials will be necessary to determine if OCPs can truly help decrease ACL injuries. Another next step will be creating a cost-effective screening blood test that accurately identifies at-risk female athletes.

Female ACL tear prevention programs

Currently, athletes are learning to protect themselves from injury through physical training programs that teach proper body mechanics. Our research indicates that most existing programs were too easy for elite sport competitors. We have created the Elite Athlete ACL Prevention program (EAP) where we push athletes to the edge of being in control. We create unstable surfaces—such as soaking wet playing fields or basketball courts made slippery by wearing socks—and ask them to perform specific maneuvers. If they are not in the mechanically appropriate position to do so, their feet will slide out from under them. With continued training, the athletes learn safer biomechanical movement patterns that, ideally, become second nature during competition. This elite program started in 2011 for several sports teams and there has been a marked decrease in knee ligament injuries after commencing the ACL prevention program.

SmartBrace Technology

A third approach in the Sports Medicine injury prevention plan is SmartBrace technology, which is an entirely different strategy compared to current knee braces. Traditional braces don’t prevent many types of injuries because they can’t effectively stabilize the knee joint in all directions. We have created a new brace with collaboration from electronic and mechanical engineers as well as prosthetics bracing specialists.

The SmartBrace senses an athlete’s movement and provides instant information through built-in computerized feedback devices. Males and females have certain movement patterns that can make them more susceptible to ligament tears and this brace identifies these patterns and gives “haptic feedback”; in other words, it vibrates in response to the wrong type of motion. If the wrong movement pattern is repeated, the brace sensors buzz again. An athlete gets a constant, real-time reinforcement to retrain themselves to move correctly.

ACL tears and Arthritis

We are currently evaluating the body’s response to ACL injury, which may damage the articular cartilage in certain athletes. This may explain why certain athletes develop early arthritis after ACL injury. Identification of cartilage injury patterns will help initiate early treatment intervention protocols to minimize the development of early arthritis in athletes.


We are currently exploring possible genetic links to ACL injury using genome wide gene correlations of injuries in patient populations greater than 110,000.

Regenerative Medicine

Platelet Rich Plasma (PRP)

This procedure involves concentrating growth factors from the patient's blood and injecting them at the site of injury to accelerate healing. We are currently investigating the use of PRP for tears to the patellar and quadriceps tendon, using a randomized controlled trial. We are also working on new formulations of PRP in the laboratory to improve clinical results.

Cellular Therapy

Cellular therapy, previously called stem cell therapy, seeks to improve the body’s healing capacity by decreasing inflammation and delivering growth factors necessary for tissue repair. We have many clinical trials ongoing, but most focus on 3 main areas:

  1. The ability to harvest cells from a patient, process them, and place them back into the patient during the same surgical procedure. Current surgical techniques require one surgery to harvest the cells, 2-3 weeks of laboratory processing, and another surgery to implant the cells. These techniques would revolutionize the use of cellular therapy in Orthopedic Surgery.
  2. Reconfigure the biologic matrices and processing to allow resurfacing of entire joint surfaces. This process would make current metal joint replacements obsolete and would allow the treatment of arthritis with the patient’s own cells.
  3. Decipher the genetic induction code and ideal matrix for meniscal cartilage engineering. This would allow the production of meniscal cartilage grafts from the patient’s own cells.
  • University of Arizona
  • Cal Poly Pomona
  • American Academy of Orthopaedic Surgeons
  • American Board of Orthopaedic Surgery
  • U.S. Ski & Snowboard
  • American Orthopaedic Society for Sports Medicine
  • University of California, Los Angeles
  • Stanford University
  • Biological Association
  • AANA Advancing the Scope