Clinical significance and evaluation of prophylactic knee brace studies in football

A review of nine studies of prophylactic knee braces in American tackle football found some support for the use of double-hinge braces in high school but little support for their use at the collegiate level. Problems with bias and confounding make it necessary that caution be exercised in the interpretation of the results of these studies, however,. To which groups these results might apply must also be considered. The two studies that assigned braces randomly found lower injury rates among high school and high-school-sized players for knee injuries and knee ligament injuries. Conversely a large, multiteam collegiate study found a significantly higher rate of knee injuries among brace users, a difference that remained when controlled for position, skill, and previous injury.     

Submaximal fatigue of the hamstrings impairs specific reflex components and knee stability

Rupture of the anterior cruciate ligament (ACL) is one of the most serious sports-related injuries and requires long recovery time. The quadriceps and hamstring muscles are functionally important to control stability of the knee joint complex. Fatigue, however, is an important factor that may influence stabilizing control and thus cause ACL injuries. The objective of this study was therefore to assess how submaximal fatigue exercises of the hamstring muscles affect anterior tibial translation as a direct measure of knee joint stability. While 15 test participants were standing upright with the knees in 30° of flexion, anterior tibial translation was induced by a force of 315 N. Two linear potentiometers placed on the tibial tuberosity and the patella recorded tibial motion relative to the femur. Reflex latencies and neuromuscular hamstring activity were determined using surface electromyography (EMG). Muscle fatigue produced a significant longer latency for the monosynaptic reflex latencies, whereas no differences in the latencies of the medium latency component were found. Fatigue significantly reduced EMG amplitudes of the short and medium latency components. These alterations were in line with significantly increased anterior tibial translation. Our results suggest that hamstring fatigue is effectively associated with mechanical loss of knee stability. This decrease in joint stability may at least in part explain higher risk of ACL injury, especially in fatigued muscles. Furthermore, we discuss why the present findings indicate that reduced motor activity rather than the extended latency of the first hamstring response is the reason for possible failure.     

A historical perspective of PCL bracing

Purpose

Currently there are many functional knee braces but very few designed to treat the posterior cruciate ligament (PCL). No PCL braces have been biomechanically validated to demonstrate that they provide stability with proper force distribution to the PCL-deficient knee. The purpose of this review was to evaluate the history and current state of PCL bracing and to identify areas where further progress is required to improve patient outcomes and treatment options.

Methods

A PubMed search was conducted with the terms “posterior cruciate ligament”, “rehabilitation”, “history”, “knee”, and “brace”, and the relevant articles from 1967 to 2011 were analysed. A review of the current available PCL knee bracing options was performed.

Results

Little evidence exists from the eight relevant articles to support the biomechanical efficacy of nonoperative and postoperative PCL bracing protocols. Clinical outcomes reported improvements in reducing PCL laxity with anterior directed forces to the tibia during healing following PCL tears. Biomechanics research demonstrates that during knee flexion, the PCL experiences variable tensile forces. One knee brace has been specifically designed and clinically validated to improve stability in PCL-deficient knees during rehabilitation. While available PCL braces demonstrate beneficial patient outcomes, they lack evidence validating their biomechanical effectiveness.

Conclusions

There is limited information evaluating the specific effectiveness of PCL knee braces. A properly designed PCL brace should apply correct anatomic joint forces that vary with the knee flexion angle and also provide adjustability to satisfy the demands of various activities. No braces are currently available with biomechanical evidence that satisfies these requirements.

Level of evidence

IV.     

A biomechanical study of the static stabilizing effect of knee braces on medial stability

The purpose of this project was to determine if commercially available braces could be shown to produce objective evidence of medial stabilization of the knee. Commercially available athletic braces were evaluated for their effect on abduction forces applied to a cadaver knee with no instability and with experimentally created medial instability. Under computer control, abduction forces were applied while simultaneous data were obtained from an electrogoniometer and transducers applied to the anterior cruciate ligament and the superficial medial collateral ligament at 0 degrees, 15 degrees, and 30 degrees of flexion. Our results showed a reduction in abduction angle using functional braces, whereas prophylactic braces demonstrated little or no protective effect.     

Knee stability in orthotic knee braces

The ability of six commercially available orthotic knee braces to stabilize ligamentous injuries of the knee was evaluated using fresh cadaver specimens. Anterior, valgus, and rotational forces were applied to the intact knee, after the anterior cruciate and medial collateral ligaments were cut, and after application of the knee braces. Bony displacement was measured using half pins and an external fixator applied to the tibia and femur. There was a significant difference in brace performance, most likely due to differences in brace design. Of the six braces tested, the 3D 3-Way Brace provided the greatest knee stability.     

Effect of bracing on the prevention of anterior knee pain—a prospective randomized study

There have been numerous reports about the use of knee braces to prevent traumatic knee injuries. Despite the frequent use of braces, very few prospective studies have been performed to study the effect of knee braces for preventing anterior knee pain syndrome (AKPS). The purpose of this study was to assess the effectiveness of a dynamic patellofemoral brace (On-Track System, dj Orthopedics) in the prevention of AKPS. 167 military recruits without history of knee pain were randomized into two groups prior to the start of their 6-week basic military training (BMT) program. The first group (brace group) consisted of 54 recruits who wore the braces for all physical activities during these 6 weeks. 113 recruits served as a control group, and followed the same 6-week strenuous training program. Chi square statistics (Fisher exact test) were used to compare the number of AKPS patients in the brace group and in the non-brace group. Our results indicated that recruits in the brace group appeared to develop significantly less anterior knee pain compared to the recruits in the control group (p =0.020). Out of the 54 recruits in the brace group, ten (18.5%) developed anterior knee pain during this study. In the control group (n =113), 42 recruits (37%) developed anterior knee pain. We conclude that the result of the present study suggests that the use of a dynamic patellofemoral brace is an effective way to prevent the development of anterior knee pain in persons undergoing a strenuous training program.The views expressed in this article are those of the author and do not reflect the official policy or position of the Belgian Department of Defense     

Prophylactic knee bracing in college football

We report on the number of knee injuries sustained by a major college football team during 2 full years when all players were required to wear laterally placed prophylactic knee braces during all practice sessions and all games. We found that the incidence rates of knee injuries were higher when the braces were worn compared to a similar period when the braces were not worn. There was also an increased number of ACL injuries during the brace period. Several indices characterizing the nature of the injuries were analyzed and were found not to be altered significantly when the prophylactic braces were used. These facts lead us to question the efficacy of prophylactic knee braces in preventing knee injuries in college football. The use of the braces was associated with increased episodes of muscle cramping in the triceps surae muscle group, required the constant attention of coaches and trainers to remind the players to wear the braces and to apply them correctly, and was costly. These findings indicate the need for other carefully controlled clinical and biomechanical studies of these devices before their routine use can be advocated.     

Evaluation of knee braces in Swedish ice hockey players.

In this retrospective investigation we have determined the rate and types of knee injuries among Swedish ice hockey players, and related these data to the use of knee braces. Thirty-seven of the originally selected 50 hockey teams (74%) of elite or first division calibre took part in the study, and 600 players answered a questionnaire. A total of 254 previous knee injuries sustained while playing hockey were reported by 243 players; tears of the medical collateral ligament (60%), meniscus (15%) or anterior cruciate ligament (12%) were the most commonly reported injuries. Prophylactic knee braces were worn by 138 (23%) of the players. Of these, 122 (88%) had earlier sustained a knee injury, and 16 had not. A total of 17 knee injuries had occurred while the players were wearing a brace. Six of these players had previously uninjured knees while 11 had repeat injury in a brace despite earlier successful rehabilitation or operation. The most common injury in braced knees was a tear of the medial collateral ligament. We conclude that the number of knee injuries is high among Swedish ice hockey players, and that the efficacy of functional knee braces to reduce knee injuries is questionable.     

Complications in the multiple-ligament-injured knee

Multiple-ligament knee injuries require careful evaluation to make an accurate diagnosis and to identify associated neurovascular injuries that can threaten limb viability. Other concomitant bony and soft-tissue injuries may include open joint injuries, fracture-dislocations, and compartment syndrome. Surgical reconstruction of multiple-ligament knee injuries requires careful preoperative planning and surgical timing to decrease the potential for iatrogenic neurovascular injuries and wound complications. Postoperative loss of motion and residual instability can result in severe functional deficits. Other complications related to surgical reconstruction may include tourniquet problems, anterior knee pain, medial femoral condyle ostenecrosis, heterotopic ossification, and compartment syndrome. This article reviews the complications that are often associated with multiple-ligament knee injuries.     

The effect of anterior cruciate ligament deficiency and functional bracing on translation of the tibia relative to the femur during nonweightbearing and weightbearing

BACKGROUND: Much of what is known about functional bracing is derived from studies of the knee during unweighted or weightbearing conditions, whereas little is known about the transition between these postures. HYPOTHESIS: Bracing the anterior cruciate ligament-deficient knee during nonweightbearing, throughout the transition to weightbearing, and during weightbearing reduces the abnormal translations of the tibia relative to the femur to within the limits of normal. STUDY DESIGN: Controlled laboratory study. METHODS: Subjects with chronic anterior cruciate ligament tears were studied with and without braces. Anteroposterior shear and compressive loads were applied to the knee, and translations of the tibia relative to the femur were measured while subjects were nonweightbearing, throughout the transition to weightbearing, and during weightbearing. RESULTS: Bracing the anterior cruciate ligament-deficient knee resulted in a significant reduction of anteroposterior laxity values, to a level within the limits of the normal knee during nonweightbearing and weightbearing postures. In contrast, when the anterior cruciate ligament-deficient knees transitioned from nonweightbearing to weightbearing, the anterior translation of the tibia relative to the femur was 3.5 times greater than in the normal knee, and bracing did not reduce this to within the limits of normal. CONCLUSIONS: Bracing a knee with a chronic anterior cruciate ligament tear was effective in reducing abnormal anteroposterior laxity during nonweightbearing and weightbearing; however, braces were not effective in reducing the abnormal anterior translations produced by the change between these postures. CLINICAL RELEVANCE: This study explains why subjects with anterior cruciate ligament tears gain partial control of pathologic anteroposterior laxity with the use of a brace but may continue to experience abnormal translations during activity.     

The efficacy of a prophylactic knee brace to reduce knee injuries in football. A prospective, randomized study at West Point

The purpose of this prospective, randomized study was to determine the efficacy of a prophylactic knee brace to reduce the frequency and severity of acute knee injuries in football in an athletic environment in which the athletic shoe, playing surface, athlete-exposure, knee injury history, and brace assignment were either statistically or experimentally controlled. The participants in the study were 1396 cadets at the United States Military Academy, West Point, New York, who experienced a total of 21,570 athlete-exposures in the 1986 and 1987 fall intramural tackle football seasons. The use of prophylactic knee braces significantly reduced the frequency of knee injuries, both in the total number of subjects injured and in the total number of medial collateral ligament injuries incurred. However, the reduction in the frequency of knee injuries (total and medial collateral ligament) was dependent on player position. Defensive players who wore prophylactic knee braces had statistically fewer knee injuries than players who served as controls. This was not true of offensive players who served as controls; they had statistically no difference in the number of knee injuries from players who wore prophylactic knee braces. The severity of medical collateral ligament and anterior cruciate ligament knee injuries was not significantly reduced with the use of prophylactic knee braces.     

The effects of functional knee bracing on muscle function and performance.

When applied, knee braces compress the soft tissues of the thigh and leg. External compression may abnormally elevate intramuscular pressure beneath the straps of the knee brace, decrease local muscle blood flow and muscular oxygenation, and induce premature muscle fatigue. Functional knee braces may give valuable support to athletes with unstable knees. They may also be a valuable rehabilitative tool in patients following surgery for knee joint instability. However, prophylactic and functional knee braces do not improve performance and may even inhibit performance in asymptomatic athletes. Athletes and coaches should be aware of the serious adverse effects of knee bracing.     

The use of knee braces during rehabilitation

This article has profiled the use of knee braces as an augmentation to the overall rehabilitation program following knee injury. It has also outlined other aspects of rehabilitation, the use of continuous passive motion devices, and other forms of exercises and training that, together with bracing, may enhance patient recovery. Continuous passive motion devices have been used for many different orthopedic problems with good success. Understanding the mechanics of how these devices move the knee and the forces that can be applied to the knee is helpful in deciding on their use after ligamentous reconstructions. Rehabilitation of the knee following surgery requires a good understanding of the effects that each exercise has on the knee and the reconstruction. Gradual progression of exercises to the knee following knee ligament reconstruction will not overstress healing tissues. Many different types of knee braces exist, and careful evaluation of them may enhance patient recovery.     

Upslope walking increases anterior tibial translation deficiency in patients with generalized joint hypermobility

BackgroundGeneralized joint hypermobility (GJH) is a highly prevalent disease that frequently affects the knee joint. The current literature has conflicting results about whether patients with GJH had knee kinematics deficiency during gait. This could be because most of the testing environment (level walking) was gentle and low-demanding for patients when studying their knee kinematics. With a high-demanding knee function and sagittal firm structure requirement, upslope walking was thought to stimulate sagittal knee kinematics deficiency in patients with GJH.Research questionsHowever, only little investigation reported whether upslope walking could stimulate knee kinematic deficiency or not. We hypothesize that upslope walking can increase sagittal knee kinematic deficiency between GJH subjects and healthy controls.MethodsA three-dimensional motion analysis was conducted to explore whether upslope walking could stimulate sagittal knee kinematic deficiency in patients with GJH. A total of 44 patients with GJH and 44 healthy controls were recruited. Subjects walked on both level and upslope (15%) conditions when the kinematic data were collected. SPM1D analysis was taken to explore the differences between groups.ResultsOur results showed that upslope walking could significantly increase knee flexion angle and anterior tibial translation in both GJH patients and healthy controls (p < 0.05). The increments of anterior tibial translation (values in upslope walking minus values in level walking) of GJH patients were greater than those of healthy controls (magnitude varying from 2.5 to 2.9 mm during 0–3% gait cycles (GC), p = 0.034; 1.4–2.9 mm during 93–100%GC, p = 0.012).SignificancesThe findings partially confirmed our hypothesis and suggested that upslope walking could increase anterior tibial translation deficiency in patients with GJH. Upslope walking may be a practical motion task in studying the weakness of knee kinematics of GJH subjects for researchers and scholars. Patients with GJH may face a more challenging knee kinematic environment than healthy controls in up-sloped activities.     

The effect of estradiol and progesterone on knee and ankle joint laxity

BACKGROUND: Female athletes suffer a higher incidence of anterior cruciate ligament injuries compared to their male counterparts, and they appear to be at increased risk for these injuries when they have increased anterior-posterior knee laxity and at specific phases of the menstrual cycle. Although the mechanism by which these factors combine to increase injury risk is unclear, studies suggest that cyclic variations in joint laxity produced by hormone fluctuation during the menstrual cycle predispose an athlete to increased risk of ligamentous injury. Little is known about whether joint laxity varies cyclically during the menstrual cycle and if so, whether it is modulated by cyclic variations of estradiol (E2) and progesterone (P4). HYPOTHESIS: Increased serum estradiol (E2) and progesterone (P4) levels are associated with increased ankle and knee joint laxity. STUDY DESIGN: Cohort study. Level of evidence, 2. METHODS: Ankle laxity, anterior-posterior knee laxity, and serum concentrations of estradiol (E2) and progesterone (P4) were measured during the menstrual cycle in women and at corresponding time intervals in men (controls). Ankle laxity was measured from stress radiographs and included anterior talar translation relative to the tibia and talar tilt relative to the tibia; anterior-posterior knee laxity was measured with the KT-1000 arthrometer. RESULTS: Women had greater knee and ankle laxity values compared to men. There was, however, no change in knee and ankle laxity over the normal menstrual cycle in women and no change over time in men. There was no relationship between estradiol and progesterone fluctuation and ankle and knee joint laxity. CONCLUSIONS: Knee and ankle joint laxities are greater for women compared to men; however, the cyclic estradiol and progesterone fluctuations that occur during the menstrual cycle do not produce cyclic fluctuations of joint laxity. Studies using joint laxity to identify a subject at risk for ligamentous injury need only consider making measurements at a specific point in time, such as during a preseason screening evaluation.     

The effect of anterior cruciate ligament reconstruction on knee joint kinematics under simulated muscle loads

BACKGROUND: Numerous studies have investigated anterior stability of the knee during the anterior drawer test after anterior cruciate ligament reconstruction. Few studies have evaluated anterior cruciate ligament reconstruction under physiological loads. PURPOSE: To determine whether anterior cruciate ligament reconstruction reproduced knee motion under simulated muscle loads. STUDY DESIGN: Controlled laboratory study. METHODS: Eight human cadaveric knees were tested with the anterior cruciate ligament intact, transected, and reconstructed (using a bone-patellar tendon-bone graft) on a robotic testing system. Tibial translation and rotation were measured at 0 degrees, 15 degrees, 30 degrees, 60 degrees, and 90 degrees of flexion under anterior drawer loading (130 N), quadriceps muscle loading (400 N), and combined quadriceps and hamstring muscle loading (400 N and 200 N, respectively). Repeated-measures analysis of variance and the Student-Newman-Keuls test were used to detect statistically significant differences between knee states. RESULTS: Anterior cruciate ligament reconstruction resulted in a clinically satisfactory anterior tibial translation. The anterior tibial translation of the reconstructed knee was 1.93 mm larger than the intact knee at 30 degrees of flexion under anterior load. Anterior cruciate ligament reconstruction overconstrained tibial rotation, causing significantly less internal tibial rotation in the reconstructed knee at low flexion angles (0 degrees-30 degrees) under muscle loads (P < .05). At 30 degrees of flexion, under muscle loads, the tibia of the reconstructed knee was 1.9 degrees externally rotated compared to the intact knee. CONCLUSIONS: Anterior cruciate ligament reconstruction may not restore the rotational kinematics of the intact knee under muscle loads, even though anterior tibial translation was restored to a clinically satisfactory level under anterior drawer loads. These data suggest that reproducing anterior stability under anterior tibial loads may not ensure that knee joint kinematics is restored under physiological loading conditions. CLINICAL RELEVANCE: Decreased internal rotation of the knee after anterior cruciate ligament reconstruction may lead to increased patellofemoral joint contact pressures. Future anterior cruciate ligament reconstruction techniques should aim at restoring 3-dimensional knee kinematics under physiological loads.     

Proprioception and joint stability

In the present paper the current clinical knowledge about proprioception is given for the shoulder, knee, ankle, elbow and the radiocarpal joint. Proprioceptive capabilities are decreased after joint injuries such as ACL or meniscus tears, shoulder dislocation, ankle sprain and in joints with degenerative joint disease. Some surgical procedures seem to restore the proprioceptive abilities; others do not. Elastic knee bandages or ankle braces increase different poprioceptive factors like ankle reproduction capability or sports-specific abilities. The present information on proprioception will influence our clinical practice in the future. We should choose surgical procedures that not only reconstruct the anatomy, but also the neurophysiologic feed-back mechanism.     

The effect of proprioceptive knee bracing on knee stability during three different sport related movement tasks in healthy subjects and the implications to the management of Anterior Cruciate Ligament (ACL) injuries

IntroductionProprioceptive knee braces have been shown to improve knee mechanics, however much of the work to date has focused on tasks such as slow step down tasks rather than more dynamic sporting tasks.ObjectiveThis study aimed to explore if such improvements in stability may be seen during faster sports specific tasks as well as slower tasks.MethodTwelve subjects performed a slow step down, single leg drop jump and pivot turn jump with and without a silicone web brace. 3D kinematics of the knee were collected using a ten camera Qualisys motion analysis system. Reflective markers were placed on the foot, shank, thigh and pelvis using the Calibrated Anatomical Systems Technique. A two way ANOVA with repeated measures was performed with post-hoc pairwise comparison to explore the differences between the two conditions and three tasks.ResultsSignificant differences were seen in the knee joint angles and angular velocities in the sagittal, coronal and transverse planes between the tasks. The brace showed a reduction in knee valgum and internal rotation across all tasks, with the most notable effect during the single leg drop jump and pivot turn jump. The transverse plane also showed a significant reduction in the external rotation knee angular velocity when wearing the brace.DiscussionThe brace influenced the knee joint kinematics in coronal and transverse planes which confirms that such braces can have a significant effect on knee control during dynamic tasks. Further studies are required exploring the efficacy of proprioceptive braces in athletic patient cohort.     

Neuromuscular biomechanical modeling to understand knee ligament loading

PURPOSE: This article examines our use of EMG-driven neuromuscular biomechanical models to study how muscles stabilize the knee. EMG can be used to establish which activation patterns are used by people for knee stabilization. However, it does not reveal the effectiveness of these patterns. The EMG-driven models provide quantitative comparisons of the effectiveness of the different knee-stabilizing activation patterns. METHODS: Subjects performed static tasks and common sporting maneuvers that challenged knee joint stability. EMG, joint posture and motion, and external forces and moments were measured during these tasks. These data were used to calibrate the EMG-driven neuromuscular biomechanical model. We then used the model to predict the role of muscles in supporting varus and valgus moments at the knee. RESULTS: We found specific muscle activation patterns to support varus and valgus moments. The most potent activation pattern to stabilize the knee is when the hamstrings or quadriceps are required to generate flexion or extension moments, respectively. The next most effective knee-stabilizing pattern is cocontraction of the hamstring and quadriceps. The small biarticular muscles at the knee provided the least support of varus and valgus moments. In the sporting tasks, sidestepping was found to place the anterior cruciate ligament at high risk of injury. We found that the muscles are the main defense against knee ligament injuries in these tasks. CONCLUSION: Traditional biomechanical and neurophysiological methods have shown that there are specific activation patterns used to stabilize the knee. By also using the EMG-driven neuromuscular biomechanical model, we have shown how effective muscles are in stabilizing the knee. This modeling method provides a new tool to understand knee joint stabilization.     

Knee Braces to Prevent Injuries in Football

In brief: Knee braces are used widely by linemen in professional and college football, and many coaches and team physicians believe the braces have reduced the number and severity of knee injuries. But questions remain about the strength of the braces, whether they prestress the knee in some cases, and, above all, whether they actually reduce injuries. This panel of team physicians says that most evidence of reduced injuries is anecdotal and that some limited evidence suggests that the braces actually increase injuries. While most of the panelists favor continued use of knee braces, they believe that more clinical and biomechanical research is necessary to establish their value.