The evolution of prophylactic knee bracing in sports.

For some coaches and athletes the term "knee brace" conjures the unpalatable image of Joe Namath and his big, bulky Lennox Hill brace from 30 years ago.

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However, the reality is very far from that. Knee bracing in sports has rapidly evolved over the past 25 years with braces becoming comfortable, highly functional and commonplace in many sports. They help protect against certain injuries and also help the athletes return to action.

The progress that has been achieved in bracing is important for high school coaches, trainers, and athletes to carefully consider.

This improved efficacy of the knee brace, particularly on a prophylactic basis, is well documented by research and very evident in the wide usage of braces among college athletes and sports programs today. As demonstrated by the studies and other data issued on the subject, braces today are an important and valuable piece of equipment that should be evaluated as early as the high-school level of athletics.

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In 1984 the most common knee brace was the single hinge lateral brace used primarily in football and it was not really designed to help players avoid injuries. In fact, the American Academy of Orthopaedic Surgeons didn't even consider injury avoidance as a primary function of knee braces due to its construction. Studies at the time were split on its ability to prevent injuries.

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Today, however, multiple studies show that modern braces have the ability to effectively control rotational forces that produce injuries in knee ligaments. The most significant development in this evolution has been the introduction of custom fit function knee braces.

THE PHYSICS OF "BRACING"

It is important for physicians and athletic trainers to advise athletes on the protective equipment. Recommendations for protection require understanding of biomechanics and anatomy. Prophylactic braces, which are worn to help avoid injuries, were initially designed to restrain abnormal knee motions, and have now progressed to provide functional stability.

Proper application has proved itself effective with the laterally applied prophylactic lateral brace as there was a decrease in valgus force application to the knee joint, which is often the culprit of injury to medial knee structures. Physicians and athletic trainers commonly use prophylactic knee braces to protect the knee from impact forces.

The principal factors that determine the impact response characteristics of a brace-knee composite are force distribution, energy absorption, and energy transmission. Material properties and the mechanical design of the brace are important factors in determining brace response to impact. The impact response can be quantified by applying lateral loads to cadaver knees and surrogate knee models.

With the knee in full extension, prophylactic braces are limited in their capacity to protect the medial collateral ligament from direct lateral stress. Laboratory studies, using a surrogate knee model, concluded that preventive braces absorb 15-30% of the energy of a direct blow.

To see an illustration of how far prophylactic bracing has come in the last twenty years one can just look at the earliest studies conducted on the topic in the mid-80s. They were mixed at best. Various authors reported on the positive effect of prophylactic bracing on the incidence and severity of knee injuries while Grace et al., and Teitz et al. reported bracing increased knee injuries.

To validate the impact of prophylactic braces on this population, a retrospective investigation attempted to control many of the known biases and utilized a large sample from a variety of institutions. Injury data was collected on 6307 football players from 71 schools in 1984 and 5445 players from 61 schools in 1985. In 1984, 36% of the players wore knee braces and in 1985, 44% of the players wore braces. In both years, preventive braces significantly increased the rate of injury (for 1984, 11.0% compared with 6.0%; for 1985, 9.4% compared with 6.4%), resulting in the conclusion that so-called preventive braces are not preventive and may in fact be harmful.

There were significantly more injuries to the medial collateral ligaments among players who wore braces (for 1984, 7.6% compared with 3.5%; for 1985, 5.4% compared to 3.6%). The increase in injuries among players who wore braces was attributed to contact. Taft et al. and Rovere and Bowen reported knee bracing as having effective difference in knee injury incidence.

UNILATERAL VS. BILATERAL HINGES

As the technology behind the bracing improved, so did the results of studies analyzing the effectiveness of prophylactic bracing. This is illustrated in the evolution of unilateral to bilateral brace hinges in the 90s. When deciding on style of brace to use, Liu reported brace designs incorporating bilateral hinges and rigid shells were more effective than unilaterally hinged designs in transmitting loads.

In the 2000 edition of Biomechanics, I reported on the comparison of knee injuries from the 1997 University of South Carolina football season when players used traditional lateral braces, vs. the 1998 season when we made the shift to bilateral custom fit knee braces that are now common. While the scope of this study is limited, the results are nonetheless very revealing as the data illustrated a substantial drop in the number and severity of knee injuries incurred.

The use of the newer custom fit braces resulted in a drastic reduction in the amount of time loss (performance) by athletes as well as a drop in economical impact (medical expenses for knee injuries) for our football program. Further studies on the subject such as a recent study on prophylactic bracing in football done by Chris Jones, ATC at the U. of Richmond in 2005-06 supported my early findings on the ability of custom knee braces to help athletes avoid injury. The coaching and athletic training community has responded by making the use of knee braces by athletes common.

PATIENT COMFORT

As an athletic trainer, I have always felt that there are two places prophylactic braces can't help: 1) around the ankle- meaning if a knee brace doesn't fit correctly, it will fall down to your ankle, or 2) in the locker. Needless to say, if the brace is not comfortable, doesn't fit, or just doesn't feel right, the athlete is not going to wear it.

I think that is one of the beautiful parts of the new functional custom-fit knee braces. They provide superior protection against knee injury, as thigh and tibial cuffs have snugger, firmer fits. Also, brace companies are continuing to develop braces that fit athletes better.

For instance DonJoy has even changed the profile of the upper thigh cuff, making it sleeker and conformed to the anatomical features of the thigh. The hinges are lower profile, making the brace much sleeker than designs of the 80's and 90's. Braces cover athletes' knees more tightly and provide more protection for soft tissue.

In a prospective, randomized study, the efficacy of bracing on the reduction of knee injuries was studied. Injuries were tabulated from intramural tackle football over two seasons. The authors studies shoes, playing surface, athlete-exposure, and knee injury history. It was found prophylactic bracing significantly reduced the frequency of medial collateral knee ligament injuries, the nemesis of college football players! Defensive players using knee braces had fewer knee injuries than controls. This finding was not true of offensive players with no difference in injuries between the brace and controls.

IN VIVO RESEARCH

More recent studies at the U. of Vermont have been applied to functional knee bracing. While the medial collateral ligament was the focus of concern in the 1980's, more attention is now paid to the protection of the anterior cruciate ligament. Intrinsic and extrinsic factors associated with these injuries have been studied. In the Vermont studies, functional knee bracing was found to provide mechanical stress protection to remodeling graft following anterior cruciate ligament reconstruction surgery.

Regardless of the time, the effect on ligamentous stress is seen. The authors found that functional braces reduced ACL strain during open-chain activity. The authors also found functional bracing had a significant strain effect on the anterior cruciate ligament in both weight bearing and non-weight bearing conditions.

FUNCTIONAL BRACE USE

Functional knee braces provide restraining influence to control abnormal displacements of the knee and decrease anterior tibial translation without associated contraction of the musculature of the lower extremity. With the ACL-deficient patient, brace use resulted in fewer episodes of giving way and utilization of the brace gave perception of stability in the knee.

In 2003, we conducted a survey to quantify prophylactic brace usage among NCAA Div. I and I-AA institutions and found that over two-thirds of the institutions responding reported embracing prophylactic brace principles for their offensive lineman in their football programs. With the cost of major knee surgery averaging around $26,000, the cost of a knee brace is minimal in comparison, never mind the loss of time and eligibility by the athlete and the possible drop in performance level a major knee injury can present.

In 2004, 24 of the top 25 ranked NCAA Div. I football teams mandated the use of knee braces to avoid injury. This rise in popularity did not happen by accident. As an athletic trainer, I believe the increased incidence of bracing has evolved both due to increased awareness and primarily due to the superior design and construction of the braces. With research from functional knee braces following anterior cruciate ligament reconstruction, we know how the braces can minimize force production on the ligaments and further apply these concepts to functional activities in rehabilitation and activity.

I think physician and health care team members need to fully understand the concepts of prophylactic bracing when making recommendations to coaches, athletes and parents relative to this subject. Why else would these teams utilize this technology if it did not work?

As I watch college football each year, the players at Florida, Ohio State, Oklahoma, Georgia, South Carolina, Florida State, Notre Dame--to name a few--have embraced prophylactic braces principles, and effectively utilized this to protect their players' knees.

Today's discussion of prophylactic bracing is totally different that the bracing concepts discussed in the 1980's. Those braces worn in sport were lateral braces and simply diffused the forces following lateral valgus blows to athlete's knees. Today, the braces are functional kneed braces with double upright hinges with bio-mechanical design to vector force away from knee ligaments.

I have had several athletes bring their brace in to me following a practice or game and I found the braces bent beyond belief, and even fractured! The design dissipates forces effectively and these players walked away from injuries with mild sprains. This scenario often is a heralding activity for the athlete and further substantiates brace usage.

I must say, it is a sickening feeling when you examine an athlete and realize that their medical collateral ligament tear and possible anterior cruciate ligament tears which were received from a clipping injury, would have been minimized and probably prevented with prophylactic brace use, as the force would have been dissipated laterally, and the double upright hinge would have also resisted the force medially.

Today, coaches, parents and athletes in high school sports are realizing that spending $350 on a standard knee brace, or even $600 for a custom brace, can be a wise investment in the effort to protect young athletes from significant knee injuries--injuries that not only can hamper a promising sports career, but also adversely affect a wide range of activities and lifestyle in later years.

And to do their part in supporting this trend, manufacturers are making it easier and more affordable for high school coaches and parents to outfit their athletes in prophylactic knee braces with programs such as DJO Inc's "Join The Club" program.

THE FUTURE OF KNEE BRACING

The bracing industry is constantly seeking newer technologies to apply to the bracing needs. Just look at how materials that are introduced rapidly make their entrance into the industry.

Further, as newer and more efficient hinges and brace composite materials evolve the product is ever improving. New dampening hinges on braces have been well received in the sports medicine community, and are now even being fabricated in a lower brace profile. Athletes seek sleek, clean designs that work.

Remember the two places braces don't work: in the locker and around the ankle!

Rod Walters has served as Head Athletic Trainer at the U. of South Carolina since March 1990. Walters coordinates the entire athletic training and rehabilitation programs for the Gamecocks and was named Director of Sports Medicine for the University in July of 2006. He is a member of the National Athletic Trainers Association (NATA) and served on their Board of Directors from 1997--2003. He was given the NATA's Most Distinguished Athletic Trainer Award in 2003 and received the associations' most prestigious award by being inducted into the Hall of Fame in 2005.

By Rod Walters, Head Athletic Trainer, Director of Sports Medicine, and assistant Athletic Director 

University of South Carolina, Columbia, SC