An overview of knee orthosis use and its role in athletic recovery
In the world of sports medicine, the use of the “knee brace” seems to be as commonplace as any other protective equipment on the field. During the last 40 years, technical advances have made knee braces lighter, stiffer, readily attainable, and at times even stylish. They can be seen strapped to a masters-level tennis player at a local club, or adorning the knee of a multimillion-dollar football player. They are commonly purchased at the neighborhood drugstore, or can be special ordered and custom fit. Knee braces can offer a psychological boost to some, almost as a warrior going to battle in a favorite type of “armor.” Many braces are used postoperatively and for return to competition. With the commonality of these devices, a critical first step for the clinician is to determine whether patients are properly educated about what indicates the use of a knee orthosis (KO), and if a KO is the right tool for the job.
When trying to understand the use of a KO, comprehensive knowledge of the knee anatomy and biomechanics (osteokinematics/arthrokinematics) is necessary. Equally important is a thorough understanding of the diagnosis and symptoms the patient is seeking to alleviate. For purposes of this article, the knee has the basic function of a hinge joint moving in the sagittal plane, with primary motion of flexion and extension occurring between the femoral condyles and the tibial plateau. Complicating matters, the axis of rotation changes as the knee goes from extension to flexion, with a combination of rolling and gliding occurring at different ratios throughout the range of motion. To a smaller degree, axial rotation occurs between the tibia and femur during flexion and extension, resulting in a slight external rotation of the tibia on the femur at end range extension, and an equally slight internal rotation at end range flexion. It becomes obvious that the complexity of knee biomechanics contributes to the equally complex concept of controlling these motions with a brace, all while allowing normal gait and human performance.1
According to the American Orthopaedic Society for Sports Medicine (AOSSM), knee bracing can be classified into three distinct categories based on their primary use: prophylactic, rehabilitative, and functional. Each of these brace types has a distinct difference in design and will be summarized in this article. Also, there are a wide variety of knee sleeves and straps that are not traditionally categorized as a KO, but are commonly used to treat knee dysfunction. Although these types of devices lie outside the scope of this article, it may be noted that what these technologies lack in stability, they can make up for in compression and proprioceptive feedback.
The prophylactic KO’s primary purpose is to protect the knee from incurring a traumatic injury. The device achieves this through several factors, including rigid collateral supports and articulating hinges positioned on both sides of the knee, Velcro straps, and—often—a tight-fitting neoprene sleeve. When properly fit and used correctly, the prophylactic KO can be a strategic piece of equipment for high risk athletes who incur large loads and forces about the knee. These braces have the challenge of allowing normal joint motion and biomechanics, while resisting motions that are potentially deleterious, eg, an external valgus load to the knee that can potentially result in damage to the medial collateral ligament (MCL), anterior cruciate ligament (ACL), and other knee structures.
Unfortunately, not all current research supports the potential benefit of prophylactic bracing. In a 2010 article, Salata and co-authors conducted a systematic review of current literature surrounding prophylactic knee bracing, and found the majority of the research available had low levels of evidence and high bias affecting the outcomes.2 They did note the American Academy of Orthopaedic Surgeons position statement on prophylactic knee braces supported use to provide limited protection against MCL injuries in football players, with less protection to the other structures of the knee.
In a 1994 study, Albright and colleagues examined the random use of knee bracing in football players in the Big 10 Conference over a 3-year period. They determined MCL injury rates and severity decreased in players who were braced during competition versus nonbraced.3 Unfortunately, there was no standardization in the type of bracing utilized and poor control for experimental bias. In 2005, a follow-up study by Najibi and Albright again looked at prophylactic brace use in football practice and competition, and reiterated that bracing is a helpful preventative tool for high-risk positions (such as linemen, linebackers, and tight ends).4 They also highlighted the importance of proper brace fit in protecting the knee, stating that custom knee braces offer a higher level of protection due in part to less migration. Specific protection for the ACL is not as likely. Both studies conclude more research is warranted.
An interesting component in the Najibi study is the mention of fatigue and blood flow changes with bracing, attributed to the strapping and pressure on the surface of the lower extremity musculature. They postulated that this may contribute to fatigue and slower sprinting in the athlete, which is something to consider when evaluating bracing usage.
When discussing rehabilitative knee bracing, the image initially conjured is of a full leg immobilizer that runs from hip to heel. Gone are the days of bulky, restrictive knee braces. They have been replaced with the latest rehabilitative braces that offer improved overall function and allow for progressive treatment. The new breed of postoperative braces is designed to be used the first day after surgery, and is modular enough to be less restrictive as time and healing allow. In general, the rehabilitative brace provides stability to the healing joint and allows for external control of range of motion, a concern during many postoperative protocols. They are most often utilized after ligamentous repairs or complicated repairs involving multiple structures in the knee. They can be locked at a certain angle, or allow for a specific range of motion early in the rehabilitative course. As healing progresses, the brace transitions toward a functional brace, with range of motion increases, until it is no longer needed.
As with the prophylactic bracing studies, the empirical evidence supporting postoperative bracing is limited. According to a 2007 article by Wright and Fetzer, the authors note that a survey of orthopedic surgeons showed that they routinely utilized protective rehabilitative bracing after ACL surgery approximately 60% of the time.5 The same survey noted approximately 63% of orthopedic surgeons recommended a sport-specific functional brace for return to sport or activity. In contrast to this survey, the authors found in their systematic review that current research did not support the use of postoperative bracing over nonbrace treatment when based on postoperative outcomes scores in patients, including measurements of pain, range of motion, graft stability, or protection from injury.
A specific type of bracing that falls in the middle ground between rehabilitative and functional is the unloader brace. Designed to produce either a frontal plane valgus or varus moment about the knee, its primary function is to unload the weight-bearing surfaces of the knee joint between the femur and tibia. One common use, as supported in the article by Wilson et al, is to utilize the brace to unweight the degenerative surfaces of the joint to reduce pain and dysfunction.6 They found that 58% of the patients who utilized the unloader brace underwent knee arthroplasty an average of 3.9 years later. They surmised that even though an unloader brace can provide short-term pain relief and improved patient function, most patients will opt for total knee replacement. The unloader brace also can be utilized postoperatively, with a specific example of younger patients undergoing cartilage restoration procedures. Orishimo and colleagues proposed that utilization of the unweighting properties would allow patients earlier mobility and increased function earlier in their postoperative protocol without jeopardizing their repair sites.7
Functional knee braces are designed primarily with the injured knee in mind, assisting in the protection of a certain aspect of the knee biomechanics to aid in healing. This also provides a reduction of symptoms and improved overall function for the patient or athlete. There can be a gray area between the use of a rehabilitative brace and functional bracing, as both provide stability to an unstable or injured knee.
In the AOSSM ACL Bracing Update, there was debate over the evidence supporting the use of functional braces in both postoperative and ACL deficient knees when returning to sport.8 The authors felt that there is validity in considering bracing and how it relates to patient outcome measures. Early mobilization and normalized ROM, along with bracing, could assist a young athlete in returning to postinjury competition. But this type of program should be considered on a case-by-case basis.
Ultimately, the use of a KO lies in the hands of the end user: the patient. The decision to pursue and utilize the brace is predicated on many considerations, such as fit, form, function, styling, price, and availability. Compliance can be a tricky topic, which often lies solely with the patient. It can be driven by many factors, such as the duration and intensity of symptoms, the riskiness of the activity being pursued, and the education/direction of the medical advisor. Proper clinical judgment should be exercised when recommending bracing for patients and athletes. Therapists should possess the ability to speak of the efficacy and practicality of the orthoses. Although not scientific, subjective reports from patients in regard to confidence level and overall function can have merit in the decision-making process.
In regard to the current body of evidence, we can summarize that many of the studies offer poor control of research parameters and bias, and are generally deficient in the support of knee bracing practices. As health care costs fall under tight scrutiny, one of two things will need to happen: an increased body of evidence supporting the use of KO will arise, or a trend of diminishing referrals and utilization of these products. RM
Brian J. Adams, PT, DPT, OCS, CSCS, is a practicing physical therapist and site supervisor at the University of Michigan MedSport—Sports Medicine Program, located in southeast Michigan. He routinely makes presentations about sports and orthopedic topics relative to the evaluation and treatment of the upper and lower extremities, and does considerable work with patients postoperatively for knee and shoulder diagnoses. As an elite-level cyclist, Adams has a special interest in the evaluation of cyclists, triathletes, runners, and other endurance athletes. For more information, contact [email protected].
1. Wolters BW. Knee orthoses for sports-related disorders. In: Hsu JD, Michael J, Fisk J, eds. AAOS Atlas of Orthoses and Assistive Devices. 4th ed. Philadelphia: Mosby-Elsevier Health Sciences; 2008:379-389.
2. Salata MJ, Gibbs AE, Sekiya JK. The effectiveness of prophylactic knee bracing in American football: a systematic review. Sports Health. 2010;2(5):375-379.
3. Albright JP, Powell JW, Smith W, et al. Medial collateral ligament knee sprains in college football. Effectiveness of preventive braces. Am J Sports Med. 1994;22:12–8.
4. Najibi S, Albright JP. The use of knee braces, Part 1: Prophylactic knee braces in contact sports. Am J Sports Med. 2005;33:602-11.
5. Wright RW, Fetzer GB. Bracing after ACL reconstruction: a systematic review. Clin Orthop Relat Res. 2007;455:162-8.
6. Wilson B, Rankin H, Barnes CL. Long-term results of an unloader brace in patients with unicompartmental knee osteoarthritis. Orthopedics. 2011;34(8):334-337.
7. Orishimo KF, Kremenic IJ, Lee SJ, McHugh MP, Nicholas SJ. Is valgus unloader bracing effective in normally aligned individuals: implications for post-surgical protocols following cartilage restoration procedures. Knee Surg Sports Traumatol Arthrosc. 2012 Aug 17. [Epub ahead of print] DOI 10.1007/s00167-012-2174-4
8. Masini BD, Owens BD. ACL Bracing Update. AOSSM: Sports Medicine Update. November/December 2011:2-6.