Knee injuries are no strangers to competitive athletes or weekend warriors. These injuries are not foreign to researchers either. In fact, the anterior cruciate ligament (ACL) deficient knee has been described in the medical literature   as far back as 1917.¹ Since that time, the medical community has devoted a significant amount of time and attention to this injury, including its cause, prevention, and surgical repair. Additionally, much research has been done to better understand the anatomy, biomechanics, and function of the ACL itself.² Despite the focus on numerous aspects of understanding the ACL deficient knee, one area that has yet to be comprehended well among the sports medicine experts is the effectiveness of functional knee bracing.

Many in the medical community support the use of functional knee braces, and even more in the general public believe they have a beneficial role, even though they have not been proven to be effective. It may seem somewhat incongruous to promote and bill for a device that has not been guaranteed to be effective. Yet, can you think of any other durable piece of equipment or therapeutic modality that comes with a guarantee? The answer is likely not, so it is therefore important to recognize the importance of the potential benefit of a functional brace for an individual, including the psychological components that may come into play. The key is to educate the public on the possible benefits without making promises or providing false optimism.

The first stabilizing knee brace that gained popularity in the athletic realm was the Lenox Hill derotation brace. This brace was developed in the latter part of the 1960s, and pioneered by New York Jets’ professional quarterback Joe Namath. The term “derotational” in the name representing a proposed function of the actual brace. It was purported to prevent the accessory tibial rotation that occurs at the knee joint when an ACL is stressed and ultimately disrupted. Soon thereafter, approximately 9,000 braces were worn by patients in the U.S. from 1976-1980.³ These functional braces have been used by athletes who sustained acute, non-operative knee injuries as well as those recovering from reconstructive knee surgery. Despite its popularity, the claims that the brace reduced anteromedial rotary instability were questioned.⁴

Throughout the 1970s and 1980s, the use of functional braces continued to increase. Empirical reports were that patients and athletes felt safer. The Sports Medicine Committee of the American Academy of Orthopaedic Surgeons convened in 1984 to obtain clinical and biomechanical data regarding the effectiveness of knee bracing.⁴ The AAOS classifies existing knee braces in four categories: a) prophylactic knee braces designed to prevent or reduce the severity of knee injuries, b) rehabilitative knee braces designed to allow protected motion of injured knees or those that have been repaired operatively, c) functional knee braces designed to provide stability for a ligament deficient knee and to provide protection for ligaments after surgical repair, and d) unloader/offloader brace designed to provide pain relief for the arthritic knee.⁵ The AAOS acknowledged the routine use of prophylactic knee braces, but could not support with scientific certainty that the number and severity of knee injuries actually decreased as a result of the functional brace.

Conflicting Evidence

While physicians prescribed functional knee braces for decades, rehabilitative specialists often fitted and monitored patients’ daily use of the brace. Rehabilitation efforts have included knee bracing for some time. Indications for use have included acute injury, such as an ACL tear, pain and instability, and protection during athletic events, especially for sports that pose a greater risk of knee injury, such as football. Those who play a high-risk sport in a potentially more precarious position, such as football linemen, are at increased risk for being hit in the knee from a blind side. Knee bracing has also been traditionally used during the acute phase of rehabilitation to protect the injured limb.⁶

Three decades later, consensus regarding the efficacy of functional knee bracing remains suspect. In a 2004 study, 100 ACL-reconstructed individuals from U.S. service academies were divided into braced and non-braced groups. The braced group was instructed to use the functional ACL brace for all cutting, pivoting, or jumping activities during the initial year following surgery. Conclusions revealed that in a young, active population, postoperative bracing did not appear to change clinical outcomes after ACL reconstruction^.7 Additional studies involving bracing of the post ACL-reconstructed knee found no evidence that pain, range of motion, graft stability, or protection from injury were associated with functional knee bracing.^8-10

Conflicting results were found in a 2006 study that looked at 820 skiers who underwent an ACL reconstruction no less than two years prior to the study. Of the original group, 257 chose to use a functional knee brace during skiing activities, and 563 subjects did not. Results revealed that the non-braced group was 2.74 times more likely to suffer subsequent knee injury than its braced counterparts.¹¹ To date, clinicians empirically report a psychological component associated with brace wearing despite an inability to quantify such observations.

The ACL deficient knee not receiving surgical intervention has received much attention as well.

In a 2008 study, three-dimensional kinematics and force platform data were used to calculate joint intersegmental forces and net joint movements for 10 healthy subjects. Results demonstrated that functional knee bracing did not alter lower limb mechanics significantly enough to reduce forces transmitted to the anterior cruciate ligament.¹²

Additionally, research in 2005 studied 95 subjects who experienced an acute tear of the ACL and randomly divided them into groups of braced and non-braced subjects. The patients were followed for 6 months and subsequent knee injuries were recorded. Upon follow-up, recorded objective measures did not find a significant difference between groups. However, subjectively the braced group reported a positive effect of bracing in regards to instability and rehabilitation that was not identified by the non-brace group.¹³

In 2006, the effects of patients with ACL deficient knees wearing a functional knee brace while running on three-dimensional kinematics and electromyography were studied. Results indicated that the group wearing a functional brace while running showed a trend to increase hamstring and decrease quadriceps activity at heel strike when compared to non-braced individuals. Furthermore, braced individuals were found to have decreased range of motion in the frontal and transverse planes. This study suggested that bracing the ACL deficient knee could alter the kinematics of the involved limb while running, thus leading to potential injury development of supportive and compensatory structural components.¹⁴

As noted above, the jury is still out as to the efficacy of functional knee bracing on both reconstructed and ACL deficient knees. With today’s emphasis on patient outcomes, is there any harm to a situation where a patient subjectively reports an increased feeling of stability as well as a positive rehabilitation outcome from brace wearing despite a lack of science to justify the perception? From the perspective of a clinician, not likely. However, third party payers might tend to think otherwise and seek out more objective proof that can be attributed to brace effectiveness.

Biomechanics of Bracing

One challenge that could be misunderstood by the average clinician is how the process of functional knee bracing actually works. With an anterior cruciate deficient knee, an individual will have excessive anterior translation of the tibia, with accompanying tibial rotational movement. This is likely to be present during both a static clinical exam and with dynamic weight-bearing functional movement. Dynamic weight-bearing activity is likely to increase the forces of translation, despite having active muscle contributions from the quadriceps and hamstring groups to assist in overall knee stability. So, in essence, a functional knee brace is a supportive passive device designed to assist the muscles in their role of stabilizing the knee.

One question that remains to be answered is if the timing of when the muscles dynamically contract plays a more important role than the actual overall strength of such muscles surrounding the knee joint. For example, a custom-designed functional knee brace on the knee of someone with excellent quadriceps and hamstring strength could still not necessarily reduce complaints of instability in a person who is ACL deficient. Why could this be? If the amount of anterior translation occurs to a point where joint stability is compromised, then no matter how strong a muscle is when it contracts, and no matter how well-fitting and durable a functional knee brace is, a person will have already experienced joint instability and performance symptoms of “giving way.” Therefore, the timing of when the muscles activate may be more important than how strong they are in general, thus reducing the importance of the functional knee brace since it is entirely passive. As a result, you may come across functional knee braces that include a component referred to as “tibial preloading.” Tibial preloading allows for a posterior-directed force of the tibia applied through tension straps when a brace is initially applied. The idea behind this is to reduce the passive nature of the external device and enhance contact of the brace to the tibia through the soft tissue components. With direct application of the brace to the bone itself, less anterior translation could occur as the tibia moves through the soft tissue structures prior to coming in contact with the brace itself.

Dollars and Sense

Prophylactic bracing has also raised many questions regarding cost effectiveness. While some insurance companies will support partial or full payment for a functional brace prescribed by a physician for an individual with an ACL deficient or reconstructed knee, many brace-wearers are left to absorb a portion of the cost. The cost of these braces can vary considerably.

Off-the-shelf functional ACL braces may range from $182.50 to $617.49 per brace.^15-17 Prophylactic bracing can become a financial burden. Despite a 1987 AAOS published statement suggesting that the routine use of prophylactic knee braces available at that time were not proven effective in reducing the incidence or severity of knee injuries in tackle football, confounding studies involving football linemen who wore similar functional braces found statistically significant effectiveness of bracing when assessing medial collateral ligament injuries.¹⁸ These findings suggest the necessity to clearly delineate the specific purported role of a “functional knee brace” prior to endorsing blanket statements related to functional knee brace efficacy. When doing so, cost containment as it relates to injury prevention and management may differ accordingly. To date, no clear studies have reported on the cost differential when comparing custom versus off-the-shelf functional knee braces.

Functional knee braces are offered in a variety of fashions that range from multiple size off-the-shelf options to custom-fit designs. The outward appearance of a custom-fitted brace is very similar to the off-the-shelf version, yet the rationale for custom fitting is to provide for better fitting and contour forming. This is a critical component to consider, because brace wearers subjectively report brace slippage as a common reason for discarding or not being compliant with wearing a functional knee brace. The custom brace does require additional time for fitting measurements, often taken by a medical professional before ordering the device. This, in turn, delays the delivery of the brace as a result of its fabrication. The custom brace, in some instances, does offer a patient some increased flexibility on options related to choosing color schemes, designs, and team logos, which may be placed on the brace. An online investigation revealed a custom brace cost range of $899.99 to $999.00.^15-16 Is the additional cost of the custom-fit brace a guarantee that the brace is superior to its off-the-shelf cousin? Not necessarily. However, if a consumer is more pleased with the aesthetics and fit of a custom measured and designed functional knee brace, the patient might be more compliant with the suggested wearing schedule. When it comes down to it, the decisions used by consumers to purchase functional knee braces are no different than buying an automobile. One can opt for a car on the lot that is purchased at a set price and includes what the car has to offer in its present condition. On the other hand, one can custom order a vehicle that most likely costs additional money, but now includes choices that please the consumer. One would like to think that a costly custom brace might be better fitting and not just more aesthetic. What about the one with the tibial preloading component? Is that custom or prefabricated? Do custom braces have varying forces in the tibial component or varying forces in valgus/varus forces?  These are important details to be considered.

In 2004, one study compared 10 medium-sized functional knee braces, custom versus off-the-shelf, and specifically looked at how each functioned during performance-related tests. During this study, mechanical testing was conducted using a servohydraulic bi-axial machine, with varus, valgus, strap tabs, and an extension-locking hinge mechanism assessed for performance. Results revealed that off-the-shelf braces scored better than the group average across performance tests.¹⁹

Despite these results, it is important to remember that the scientific literature regarding brace function remains speckled, and a significant amount of patient perception of brace satisfaction may override future scientific studies that do not support functional knee braces.

The Ins and Outs of Brace Wearing

Regardless of evidence for or against functional knee bracing, consumers of the product will formulate their own opinions once they are prescribed a brace to wear. A functional knee brace could be one of the most effective devices on the proven market, yet there are some practical wear issues that need to be considered. A common concern relates to the fitting of the brace itself. Braces tend to be more loose-fitting versus tight-fitting in general, and develop what is called “brace slippage.” Slippage can occur simply from having straps too loose around the tibia or femur, or it can occur over time when a person wearing a brace perspires. Sweat that accumulates along one’s leg tends to reduce the friction between the brace and the skin, allowing for the brace to slide down the leg with continued activity.

Manufacturers have attempted to prevent brace slippage by implementing a neoprene sleeve as an undergarment whereby the outer layer connects to the brace via a Velcro-like adherence. Overall, this has been subjectively reported to be an effective intervention, though it has led to two additional unanticipated brace-wearing challenges. First, the Velcro material that connects the brace to the neoprene sleeve is so effective that it actually creates a challenge when one dons the brace. The brace tends to catch on the material, making it rather arduous to pull the brace up from the foot to the thigh. Second, skin irritation has been reported by many individuals. In some cases this has been due to the material itself, while in others it is simply a result of the friction associated with the movement between the brace, material, and skin.

One significant feature often overlooked in functional knee brace wearing is customer service. This is most important when one experiences faulty equipment. No brace is perfectly designed, and even normal wear and tear can lead to broken parts. This can include hinges, straps, or any other component of a knee brace. Being able to successfully access customer service representatives from a manufacturer assures one that the expenses devoted toward a functional knee brace include some form of warranty on the item. Although there may be additional charges for parts that break down through unconventional or unaccepted methods of brace use, it is important to understand the red tape and have access to customer assistance in a timely, friendly, and competent manner.

The future of functional knee bracing is exciting. As research continues, the efficacy of functional knee bracing and its role in preventing and managing knee injuries will expand. We may see new designs that are purported to protect ligaments in ways never before discussed. Recent examples of brace use include a 2007 study that found using a functional knee brace that unloads forces from the medial compartment of the knee in individuals who have medial compartment osteoarthritis assists in reducing pain and disability. Something that has not changed in the medical community since the 1960s is the fact that many opinions still exist regarding whether there is a confirmed role for functional knee brace wearing.²⁰ The research thus far is inconclusive.

Perhaps further studies will more convincingly support the clinical findings that suggest pain relief and joint support with the knee brace. These findings concur with earlier studies identifying functional knee braces to assist in load sharing and thus reduce joint stresses in individuals with degenerated medial compartment of the knee. The results were of interest in the fact that joint stresses were decreased in their subjects despite any significant changes in angulation of the joint.²¹ Most recently, a systematic review reported that the use of prophylactic knee braces in the prevention of knee injuries in collegiate football players can be neither advocated nor discouraged, suggesting continued emphasis on future studies.²²

Who are Candidates?

Determining which individuals would benefit most from wearing a functional knee brace is a challenge that will hopefully become easier as more outcomes become available regarding usage patterns. Patient preference may ultimately be decided upon not only by successful brace wearing outcomes, but also by other intangibles such as customer service, brace comfort, durability, and ease of application. After all, one could view the wearing of a brace similar to that of an athletic shoe – one size doesn’t fit all!

Medicine has drastically changed since the 1960s. Many pictures have been published of the popular football player Joe Namath wearing a Lenox Hill derotation brace. The underlying question is: did the brace that he wore and made so popular buy him additional successful years in the NFL? Clinicians might also ask if the anatomical support of such a brace is statistically significant enough to provide postoperative ACL patients with better overall outcomes. Does wearing a prophylactic knee brace even provide a cost-effective option to reducing knee injuries? The answers to all of these questions will hopefully arise as we continue to learn more about functional knee bracing. Additionally, consumer interest, perception, and demand will contribute to the decision-making process of how the medical community determines what the definition of an appropriate candidate for brace wearing is. Perhaps there will be another athlete with Joe Namath’s stature who defies scientific research and whose public persona contributes to the endorsement of the next generation of functional knee bracing.