Medial collateral ligament knee sprains in college football. Brace wear preferences and injury risk

Prophylactic Knee Bracing in Offensive Linemen of the National Football League: A Retrospective Analysis of Usage Trends, Player Performance, and Major Knee Injury

Background

Offensive linemen in American football are prone to high-energy valgus forces to the knee, leading to associated injuries. Some offensive linemen in the National Football League (NFL) wear prophylactic knee braces (PKB) to prevent ligamentous injury.

Purpose/Hypothesis

This purpose of the study was to compare injury rates and performance between NFL offensive linemen who wear PKB and those who do not. It was hypothesized that brace wear would be associated with fewer major knee injuries and no difference in gameplay performance.

Study Design

Cohort study; Level of evidence, 3.

Methods

For the 2014 through 2020 NFL seasons, offensive linemen with at least 200 game snaps per regular season were identified. Players were grouped by PKB status (bracers vs nonbracers) based on visualization of bilateral, dual-hinged metal knee braces as part of gameday uniforms on publicly available imaging databases and/or game videos. Major knee injuries, defined as those requiring the missing of games, were identified using publicly available data. Performance was assessed with Pro Football Focus grades for each season. Rates of major knee injury were compared between groups with the 2-sample Z test for proportions, and performance grades were compared with the unpaired t test.

Results

For the cumulative study period, bracers demonstrated a significantly lower rate of major knee injuries than nonbracers (0.013 vs 0.049 injuries per player, respectively; P = .04). Isolated MCL injury was the most common injury for nonbracers. There was no group difference in performance for the cumulative study period or during most individual seasons. Yearly prevalence of PKB usage declined steadily from 16.3% in 2014 to 5.6% in 2020. A subgroup analysis of rookie players demonstrated an overall downtrend in usage during the study period as well.

Conclusion

Results indicated that knee brace prophylaxis by NFL offensive linemen was associated with a reduced risk of major knee injury without a significant difference in performance when compared with nonbracers. Despite this, the prevalence of PKB declined over the study period.

Efficacy of Prophylactic Knee Bracing in Sports

Anterior cruciate ligament (ACL) and medial collateral ligament (MCL) injuries are common knee injuries, which can result from contact and noncontact during sports, recreation, or work-related activities. Prophylactic knee braces (PKBs) have been designed to protect the knee and decrease risk of recurrence of these injuries. Despite their success, PKBs have not been proven to be consistently effective and cost of the device must be evaluated to optimize its use in sports, particularly American football. Biomechanical studies have suggested that increased hip and knee flexion angles may reduce frontal plane loading with bracing which can protect the knee joint. This is essential with knee loading and rotational moments because they are associated with jumping, landing, and pivoting movements. The clinical efficacy of wearing PKBs can have an impact on athletic performance with respect to speed, power, motion, and agility, and these limitations are evident in athletes who are unaccustomed to wearing a PKB. Despite these concerns, use of PKBs increases in patients who have sustained an MCL injury or recovering from an ACL reconstruction surgery. As the evidence continues to evolve in sports medicine, there is limited definitive data to determine their beneficial or detrimental effects on overall injury risk of athletes, therefore leading those recommendations and decisions for their usage in the hands of the athletic trainers and team physicians' experience to determine the specific brace design, brand, fit, and situations for use.

Overview of Sport-Specific Injuries

Athletes are at risk for a variety of injuries not typically sustained in everyday life. The team physician must be capable of not only identifying and treating injuries as they occur, but he or she must be armed with the knowledge to minimize the risk of injuries before they occur. This review serves to provide an overview of the various sport-specific injuries typically encountered by team physicians. Injuries are grouped by body part and/or organ system, when possible. We do not aim to cover in detail the various treatments for these injuries; rather, we hope that this article provides a comprehensive overview of sport-specific injury, and demonstrate the well-roundedness in skills that must be possessed by team physicians.

The NFL's Chop-Block Rule Change: Does It Prevent Knee Injuries in Defensive Players?

Background:

The chop block, a football maneuver in which an offensive player blocks an opponent around the thigh while another offensive player engages the same opponent above the waist, was declared illegal by the National Football League (NFL) before the 2016-2017 season. Chop blocks have been hypothesized to be associated with medial collateral ligament and anterior cruciate ligament injury, especially in offensive/defensive linemen.

Purpose:

To quantify the impact that the chop-block rule change had on the incidence of knee injuries to defensive players in the NFL over 4 seasons (2014-2018).

Study Design:

Cohort study; Level of evidence, 3.

Methods:

NFL injury data for all defensive players from regular-season games played from 2014 through 2018 were collected. For this study, all knee injuries were attributed to competitive game play. Injury rates were reported as the number of injuries per 1000 athletic exposures (with 95% CIs).

Results:

A total of 256 games were played during the 2014-2015, 2015-2016, 2016-2017, and 2017-2018 NFL regular seasons, and all were included in this study. Among defensive players, the relative risk for a knee injury per 1000 athletic exposures was 0.84 (95% CI, 0.75-0.96) for the 2 seasons after the chop-block rule change (2016-2017 and 2017-2018) versus the 2 seasons before (2014-2015 and 2015-2016) (P = .009). Thus, the relative risk reduction was 16%. The relative risk for a defensive player to be placed on injured reserve per season was 0.90 (95% CI, 0.72-1.13) for the 2 seasons after the rule change versus the 2 seasons before (P = .39).

Conclusion:

The NFL’s recent ruling against in-game chop blocks may have reduced the incidence of knee injuries among defensive players.

Medial Collateral Ligament Reconstruction in Patients With Medial Knee Instability: A Systematic Review

Background:

The medial collateral ligament (MCL) is the most frequently injured ligament of the knee, but it infrequently requires surgical treatment. Current literature on MCL reconstructions is sparse and offers mixed outcome measures.

Purpose/Hypothesis:

The purpose of this study was to compare the outcomes of isolated MCL reconstruction and multiligamentous MCL reconstruction. Our hypothesis was that in selective patients, MCL reconstruction would significantly improve objective and subjective patient knee performance measures, those being baseline valgus laxity, range of motion, objective and subjective International Knee Documentation Committee (IKDC) scores, Tegner score, and Lysholm knee activity scores.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines and utilizing 3 computer-based databases. Studies reporting clinical outcomes of patients undergoing MCL reconstruction due to chronic instability or injury with mean follow-up of at least 2 years and levels of evidence 1 to 4 were eligible for inclusion. All relevant subject demographics and study data were statistically analyzed using 2-sample and 2-proportion z tests.

Results:

Ten studies involving 275 patients met our inclusion criteria. Of these patients, 46 underwent isolated MCL reconstruction while another 229 underwent reconstruction of the MCL in addition to a variety of concomitant reconstructions. Overall outcomes for all patients were significant for (1) reducing the medial opening of the knee (8.1 ± 1.3 vs 1.4 ± 1.0 mm; P < .001), (2) improving the patient’s objective IKDC score (1.2% vs 88.4%; P < .001), (3) improving the patient’s subjective IKDC score (49.8 ± 6.9 vs 82.4 ± 9.6; P < .001), and (4) improving the Lysholm knee activity score (69.3 ± 5.9 vs 90.5 ± 6.6; P < .001). No differences existed between concomitant reconstruction groupings except that postoperative Lysholm scores were better for MCL/anterior cruciate ligament reconstruction than MCL/posterior cruciate ligament reconstruction (94.3 ± 4.5 vs 84.0 ± 11.7; P < .001). Normal or nearly normal range of motion was obtained by 88% of all patients.

Conclusion:

The systematic review of 10 studies and 275 knees found that the reported patient outcomes after MCL reconstruction were significantly improved across all measures studied, with no significant difference in outcomes between concomitant reconstructions.

Trends in Authorship Characteristics in The American Journal of Sports Medicine, 1994 to 2014

BACKGROUND

Trends in author qualifications, the number of authors per article, and the internationalization of author groups in sports medicine journals have not been widely investigated.

PURPOSE

To examine trends in authorship characteristics in a single prominent sports medicine journal.

STUDY DESIGN

Systematic review.

METHODS

Articles published in The American Journal of Sports Medicine (AJSM) in 1994, 2004, and 2014 were reviewed. For each article, the academic degree(s) of the first and last author, the total number of authors, the country of the author group, and academic institution status were recorded.

RESULTS

A total of 708 articles met the inclusion criteria: 129 in 1994, 244 in 2004, and 335 in 2014. There were significant differences in the proportion of first authors with an MD degree (80% in 1994, 75% in 2004, 67% in 2014; P = .01), a dual MD/PhD degree (4.7% in 1994, 6.2% in 2004, 9.3% in 2014; P < .001), and a bachelor's degree (0% in 1994, 0% in 2004, 3.9% in 2014; P < .001). The proportion of last authors with an MD/PhD significantly increased over the 2 decades studied (7% in 1994, 13% in 2004, 17% in 2014; P = .01). The mean number of authors per article also significantly increased (3.8 in 1994, 4.3 in 2004, 5.8 in 2014; P < .0001). The proportion of articles published by an international group and the proportion of articles published by an academic institution increased over the 20-year span as well (both P < .0001).

CONCLUSION

Within the past 2 decades, there has been a significant increase in the average number of authors per article in AJSM, as well as a higher proportion of international groups and academic institutions publishing in the journal. More nonphysicians are publishing in AJSM, with a significantly higher percentage of first authors with a bachelor's degree as their highest degree. This is likely due to a combination of a general increased interest in research as well as increased competition among medical students. These factors have likely led to larger research groups and thus a significantly higher average number of authors per article.

The epidemiology of medial collateral ligament sprains in young athletes

BACKGROUND

A medial collateral ligament (MCL) knee sprain is a prevalent injury in athletic populations that may result in significant time lost to injury. Remarkably little is known of the epidemiology of this injury.

PURPOSE

To define the incidence of MCL tears and to determine the demographic and athletic risk factors.

STUDY DESIGN

Descriptive epidemiological study.

METHODS

A longitudinal cohort study was performed to examine the epidemiology of isolated MCL sprains at the United States Military Academy (USMA) between 2005 and 2009. Charts and radiographic studies were reviewed by an independent orthopaedic surgeon to identify all new isolated MCL sprains resulting in time lost to sport and activity that occurred within the study period. Incidence rates (IRs) with 95% confidence intervals (CIs) were calculated per 1000 person-years at risk and by sex, sport, and level of competition. The IR per 1000 athlete-exposures (AEs) was also determined. Incidence rate ratios (IRRs) and respective 95% CIs were calculated between male and female students, intercollegiate and intramural athletes, and male and female intercollegiate athletes involved in selected sports. Chi-square and Poisson regression analyses were used to examine the relationship between the variables of interest and the incidence of MCL sprains, with statistical significance set at P < .05.

RESULTS

A total of 128 cadets sustained isolated MCL injuries during 17,606 student person-years from 2005 to 2009. This resulted in an IR of approximately 7.3 per 1000 person-years. Of the 128 injuries, 114 were in male athletes (89%) and 14 were in female athletes (11%). Male cadets had a 44% higher IR than did female cadets (7.60 vs 5.36, respectively), although this was not significant (P = .212). Of 5820 at-risk intercollegiate athletes, 59 (53 male, 6 female) sustained an isolated MCL sprain during 528,523 (407,475 male, 121,048 female) AEs for an overall IR of 10.14 per 1000 person-years and 0.11 per 1000 AEs. The IRR of MCL sprains of men compared with women involved in intercollegiate athletics was 2.87 (95% CI, 1.24-8.18) per 1000 person-years and 2.62 (95% CI, 1.13-7.47) per 1000 AEs. Of 21,805 at-risk intramural athletes, with quarterly participation, 16 (all male) sustained isolated MCL injuries during 225,683 AEs for an overall IR of 0.07 per 1000 AEs. The IRs of MCL injuries of intercollegiate and intramural athletes did not differ significantly. In intercollegiate sports, wrestling (0.57), judo (0.36), hockey (0.34), and rugby (men's, 0.22; women's, 0.23) had the highest IRs per 1000 AEs. When examining men's intercollegiate athletics, the IRRs of wrestling (13.41; 95% CI, 1.80-595.27) and hockey (8.12; 95% CI, 0.91-384.16) were significantly higher compared with that of lacrosse. Among women's intercollegiate sports as well as intramural sports, there were no significant differences in IRs. A median of 16 days was lost to injury, with 2407 total days lost for all injuries. Grade 1 MCL injuries lost a median of 13.5 days, while higher grade injuries lost a median of 29 days.

CONCLUSION

Medial collateral ligament injuries are relatively common in athletic cohorts. The most injurious sports are contact sports such as wrestling, hockey, judo, and rugby. Male athletes are at a greater risk than female athletes. Intercollegiate athletes are at a greater risk than intramural athletes. The average amount of time lost per injury was 23.2 days, with greater time lost with higher grade sprains than grade 1 sprains.

Ligamentous injuries of the knee: anterior cruciate, medial collateral, posterior cruciate, and posterolateral corner injuries

This article discusses athletic injuries of the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and posterolateral corner. Best evidence to date validates that conservative management of ACL ruptures is a reasonable strategy. Current data also seem to advocate nonoperative management of PCL injuries. All isolated MCL injuries, regardless of grade, are usually treated with a brief period of immobilization and symptomatic management. Although the surgical literature often advocates surgical treatment of posterolateral corner injuries, there have been no randomized trials substantiating that these injuries are best treated surgically.

The effectiveness of prophylactic knee bracing in american football: a systematic review

Context:

Knee injuries, particularly of the medial collateral ligament (MCL), are the most common injury sustained in American football. In 1979, Anderson et al described a knee brace that could protect uninjured knees from MCL injuries resulting from lateral impact. Since then, a number of light and free-moving bracing devices have been developed. However, the efficacy of prophylactic knee bracing remains in question.

Objective:

A systematic review of the efficacy of prophylactic knee bracing in preventing MCL injuries in football players.

Data Sources:

Based on MedSearch and PubMed, articles from 1985 to November 2009 were identified with the following keywords and their combinations: prophylactic, prevent injury, knee brace, prevention, medial collateral ligament, MCL, football, and bracing.

Study Selection:

One randomized controlled trial (level 1 study) and 5 prospective cohort studies (level 2 studies) were selected.

Results:

The results of the studies were inconsistent; only 1 study showed that prophylactic knee bracing significantly reduced MCL injuries (P < .05). In contrast, 2 studies found that knee bracing was associated with an increase in knee injuries.

Conclusions:

Prophylactic bracing in American football has not consistently reduced MCL injuries. There remains a lack of evidence to support the routine use of prophylactic knee bracing in uninjured knees. There is limited high-level evidence, bias in the available literature, and confounding variables that limit the current literature.

The effect of prophylactic knee bracing on performance: balance, proprioception, coordination, and muscular power

PURPOSE

Prophylactic knee braces are largely used in the prevention of ligament injuries, but their effectiveness on performance are still controversial. The aim of this study was to determine which brace was the most effective on functional performance.

METHOD

Twenty-four healthy subjects (14 men and 10 women), between the age of 18 and 22 with no prior history of lower limb injury and brace use, voluntarily participated in this study. Five different prophylactic knee braces were used. The test protocol consisted of dynamic balance, jumping performance, proprioception, coordination, and maximal force. Balance was assessed by the Y balance test; jumping performance was assessed by vertical jump and one-leg hop tests; maximal force, proprioception, and coordination were assessed by using functional squat testing. Proprioceptive test was performed by using the functional squat system machine that the participants were instructed to keep the crosshair on the line, even after the visual aid had disappeared. The subjects without a brace and with the brace by using 5 different braces (DonJoy-USA) were evaluated by five different therapists.

RESULTS

Hinged "H" buttress for the support of the knee brace was found to be more effective than the others in terms of balance. Drytex economy hinged knee brace had the best result in terms of proprioception and maximal force. There were no significant differences in vertical jump and one-leg hop tests (n.s.).

CONCLUSION

In conclusion, the hinged "H" buttress for support of the knee brace and Drytex economy hinged knee brace produced the best results on the performance parameters. The other three braces demonstrated more variable and less optimal results. Prophylactic knee braces can be used for both healthy subjects and athletes to enhance proprioception, coordination, maximal force, and balance, but it is important to choose the best proper brace to the individuals according to their fitness level.

LEVEL OF EVIDENCE

(Economic and decision analysis-developing an economic or decision model), Level II.

Performance of healthy braced participants during aerobic and anaerobic capacity tasks

CONTEXT

Knee braces were introduced in sports approximately 30 years ago. However, the effects of a functional knee brace (FKB) on aerobic and anaerobic performance after fatigue are unknown.

OBJECTIVE

To investigate whether FKB use in noninjured participants hindered performance during aerobic (Léger beep test) and anaerobic (repeated high-intensity shuttle test [RHIST]) tasks.

DESIGN

Crossover study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty-seven healthy male provincial and national basketball and field hockey athletes (age = 19.4±3.0 years, range, 17-26 years; height = 182.6±6.8 cm, range, 168-196 cm; mass = 80.0±9.1 kg, range, 66-108 kg).

INTERVENTION(S)

Each participant was provided a custom-fitted FKB and performed 5 nonbraced (NBR) testing sessions over 3 days, followed by 5 braced (BR) testing sessions over 3 days, for a total of 17.5 hours of testing per condition. During each testing session, participants performed 1 trial of the Léger beep test and 1 trial of the RHIST in each condition.

MAIN OUTCOME MEASURE(S)

Predicted maximal oxygen consumption (Vo(2) max) and time performance measures were recorded for each NBR and BR trial.

RESULTS

Initial performance levels were lower for BR than NBR for both the Léger beep test (BR = 44.3 mL/kg/min, NBR = 47.3 mL/kg/min; F(1,26) = 8.726; P = .007) and the RHIST (BR = 16.5 seconds, NBR = 16.2 seconds; F(1,26) = 13.98, P = .001). However, with continued FKB use, the aerobic performance measure remained higher for only the first 2 BR testing sessions (NBR = 46.9 mL/kg/min, BR = 42.4 mL/kg/min; F(3.0,79.8) = 4.95, P = .003). For the anaerobic test, no performance difference was noted between the testing conditions (NBR = 16.2 seconds, BR = 16.4 seconds; P = .7), whereas fatigue levels were lower during BR testing sessions (NBR = 33%, BR = 31%). After 14.0 hours of FKB use, performance levels were almost equal between the testing conditions (NBR = 47.6 mL/kg/min, BR = 46.1 mL/kg/min).

CONCLUSIONS

We found an initial decrement in performance when the FKB was used during an aerobic or anaerobic task. However, after 14.0 hours of FKB use, accommodation to the FKB was possible.

Knee injuries and the use of prophylactic knee bracing in off-road motorcycling: results of a large-scale epidemiological study

BACKGROUND

The effectiveness of prophylactic knee bracing in preventing knee injuries during sports has been evaluated; however, because of the variability in study conclusions, the topic remains controversial. Despite a paucity of data, the authors believe that prophylactic knee bracing is frequently used in off-road motorcycling.

HYPOTHESIS

No statistically significant difference exists in the frequency and types of knee injuries incurred between braced and nonbraced riders using commercially available knee braces in off-road motorcycling.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

Data from 2115 off-road motorcycle riders was obtained using an Internet-based survey over a 1-year period. Participants were grouped by use or nonuse of prophylactic knee bracing, and an incidence rate ratio was used for injury rate comparison.

RESULTS

Participants recorded 39 611 riding hours over the study period. A total of 57 riders (2.7%) sustained at least 1 knee injury, for a total of 89 injuries. The most common injuries involved the anterior cruciate ligament, menisci, and medial collateral ligament. There was a significantly higher rate of overall injuries in the nonbraced group versus the braced group (3.675 vs 1.587 per 1000 rider hours, P < .001). Significantly higher incidence rates of anterior cruciate ligament rupture (1.518 vs 0.701 per 1000 rider hours, P = .0274) and medial collateral ligament injury (0.799 vs 0.111 per 1000 rider hours, P = .002) were found among nonbraced riders compared with braced riders.

CONCLUSION

The most common knee injuries in off-road motorcycling involve the anterior cruciate ligament, menisci, and medial collateral ligament. The use of prophylactic knee bracing appears to have a beneficial effect in preventing medial collateral ligament and anterior cruciate ligament injuries as well as overall knee injury occurrence. These findings may be applicable to other sports that involve similar forces and mechanics.

Management of medial-sided knee injuries, part 1: medial collateral ligament

The medial collateral ligament complex is a primary stabilizer that combines static and dynamic resistance to direct valgus stress while contributing significant restraints to rotatory motion and anterior-posterior translation. Varying opinions exist among investigators regarding injury classification and treatment algorithms. Whereas most agree that the majority of isolated medial collateral ligament complex injuries can be treated nonoperatively, isolated injuries with chronic instability and multiligament injuries may require operative intervention. Substantial confounding factors are present within published reports, making comparative analyses and systematic review challenging. This review focuses on the anatomy and biomechanics of the medial structures of the knee; it discusses the clinical evaluation of complex injuries; and it reviews nonoperative and operative treatment methods.

Medial collateral ligament injuries of the knee: current treatment concepts

The medial collateral ligament is one of the most commonly injured ligaments of the knee. Most injuries result from a valgus force on the knee. The increased participation in football, ice hockey, and skiing has all contributed to the increased frequency of MCL injuries. Prophylactic knee bracing in contact sports may prevent injury; however, performance may suffer. The majority of patients who sustain an MCL injury will achieve their pre-injury activity level with non-operative treatment alone; however, those with combined ligamentous injuries may require acute operative care. Accurate characterization of each aspect of the injury will help to determine the optimum treatment plan.

Management of medial collateral ligament injuries in the knee: an update and review

The medial collateral ligament (MCL) is the most frequently injured ligament in the knee, with mild-to-moderate tears often going unreported to physicians. Medial collateral ligament injuries can result from both contact and noncontact sporting activities. The mainstay of treatment is nonoperative; however, operative management of symptomatic grade II and grade III injuries is considered when laxity and instability persist. The timing of surgical repair in the setting of a multiligament knee injury remains an area of controversy among surgeons, with proponents of early reconstruction of the anterior and posterior cruciate ligaments and nonoperative management of the MCL versus proponents of delayed reconstruction following nonoperative treatment of the MCL. Prophylactic bracing may continue to increase and evolve as bracing technology improves and athletic cultures change.

Treatment of medial collateral ligament injuries

The medial collateral ligament is the most frequently injured ligament of the knee. The anatomy and biomechanical role of this ligament and the associated posteromedial structures of the knee continue to be explored. Prophylactic knee bracing has shown promise in preventing injury to the medial collateral ligament, although perhaps at the cost of functional performance. Most isolated injuries are treated nonsurgically. Recent studies have investigated ligament-healing variables, including modalities such as ultrasound and nonsteroidal anti-inflammatory drugs. Concomitant damage to the anterior or posterior cruciate ligaments is a common indication to surgically address the high-grade medial collateral ligament injury. The optimal treatment of multiligamentous knee injuries continues to evolve, and controversy exists surrounding the role of medial collateral ligament repair/reconstruction, with data supporting both conservative and surgical management.

Current evidence and clinical applications of therapeutic knee braces

Braces are commonly used for the management of musculoskeletal injuries. With improvements in design and application, the knee brace has gained recognition by many as a treatment and prevention modality. However, there exist many different categories of knee braces, leading to confusion among many end users. The theoretical basis of the mechanism of action of the unloader, prophylactic, patellofemoral, and functional knee braces are explained in this review. This article also provides an update on the various knee braces in terms of the clinical efficacy and appropriate prescription recommendations.

Use of discretionary protective equipment in high school athletes: prevalence and determinants

OBJECTIVES

We sought to describe the use of discretionary protective equipment among high school athletes and to examine social and behavioral determinants contributing to equipment usage.

METHODS

We analyzed data from a 3-year (1996-1999), stratified, 2-stage cluster sample of athletes engaged in 12 organized sports in 100 North Carolina high schools (n=19728 athlete-seasons) (an athlete-season represents an individual student who participates in a particular sport in a particular season). We used generalized logistic regression to model the association of social and behavioral determinants and demographic variables with discretionary protective equipment use.

RESULTS

About one third of high school athletes self-reported using lower extremity discretionary protective equipment. Girls, seniors, those who played limited-contact sports, and those who played multiple sports reported higher usage. Small school size, low player/coach ratio, high proportion of team usage, and history of previous lower extremity injury were important predictors of usage. Coaches' experience, qualifications, and training, however, were not predictive of usage.

CONCLUSIONS

Intervention efforts to promote use of discretionary protective equipment need to target school-level factors and should consider both team requirements and the role of peers in setting and reinforcing norms.

The use of knee braces, part 1: Prophylactic knee braces in contact sports

Surrogate knee model biomechanical studies have indicated that off-the-shelf braces provide 20% to 30% greater resistance to a lateral blow when the knee is in full extension. Custom functional braces doubled the protective effects and proved effective with the knee in some flexion. Although functional performance studies are not consistent, preventive knee braces may slow straight-ahead sprint speed, cause early fatigue, and increase muscular relaxation pressures, energy expenditure, blood lactate levels, maximal torque output, oxygen consumption, and heart rate. Two epidemiologic studies have been performed. At West Point, a randomized control study of 71 injuries in 1396 cadets indicated knee brace effectiveness with a statistically higher rate of injury in the control group (3.4/1000 exposures) than in the braced group (1.5/1000 exposures), with the most significance for medial collateral ligament sprains in defensive players. The Big Ten Conference conducted a descriptive study of 100 medial collateral ligament sprains among 987 players in different positions, strings, and types of session. Brace-wear tendency varied directly with the unbraced player counterpart's risk of medial collateral ligament sprain, with the nonplayer linemen experiencing both the greatest risk of unbraced practice session injury (0.0801 injuries/1000 exposures) and the highest incidence of brace wear (85%). During practices, there was a nonsignificant but very consistent reduction in injury rate for braced players in every position and string. During games, there was also a reduced rate for linemen and the linebacker/tight end group. The study concluded that although the issue is not closed, preventive knee braces appear to offer some protection to the medial collateral ligament from a contact injury involving a valgus blow, but there may be negative effects on performance level, leg cramping, and fatigue symptoms.

Use of discretionary protective equipment and rate of lower extremity injury in high school athletes

Use of protective equipment is an important sports injury prevention strategy, yet use of protective equipment by high school athletes has seldom been studied. The authors analyzed data from a 3-year (1996-1999), stratified, two-stage cluster sample of athletes from 12 organized sports in 100 North Carolina high schools (n = 19,728 athlete-seasons). Information on each athlete's use of protective equipment and prior injury was collected during the preseason. Prospective information on injuries and weekly participation in games and practices was collected during the playing season. Use of lower extremity discretionary protective equipment tended to decrease the overall rate of lower extremity injury (rate ratio (RR) = 0.91, 95% confidence interval (CI): 0.72, 1.15). However, this slight protective effect was entirely due to kneepad use (for knee injury, RR = 0.44, 95% CI: 0.27, 0.74). Knee brace use and ankle brace use were associated with increased rates of knee injury (RR = 1.61, 95% CI: 1.08, 2.41) and ankle injury (RR = 1.74, 95% CI: 1.11, 2.72), respectively. This could be due to slippage of the brace during use, increased fatigue due to the energy cost of wearing a brace, or bias in the study. Further investigation into the effects of brace use is warranted.

Injury patterns in big ten conference football

BACKGROUND

In 1998, the National Collegiate Athletic Association legislated a decrease in the number of scrimmages and full-contact practices allowed during the spring season.

HYPOTHESIS

A significantly increased risk of injury faced by the same player during the spring versus fall practice sessions does exist, but the National Collegiate Athletic Association regulations will not have the intended effect of reducing injury rates to equal or below those of the fall practice sessions.

STUDY DESIGN

Retrospectively analyzed, descriptive study of prospectively collected injury surveillance data followed by a prospective, controlled, repeated-measures study after the rule change.

METHODS

Phase 1: the Big Ten Conference Sports Injury Surveillance System database was reviewed from spring 1992 through fall 1997 for all reportable injuries. Phase 2: a prospective investigation was instituted from spring 1998 through fall 2000. This protocol was modified to also document updated individual player position descriptions and string as well as exposures for the old fall and spring practice categories (scrimmages, full contact, and limited contact) and the new spring practice designations (full pads with and without tackling, helmets only, spring game, and other scrimmages).

RESULTS

Phase 1: There were 3950 fall injuries and 1007 spring injuries, with 469 of the 1007 attributable to the "spring risk factor." There was a statistically significant increase in injury rate in the spring (19.8) versus fall (10.6). Scrimmages (incidence density ratio = 2.4) and limited-contact practices (incidence density ratio = 2.5) showed more than twice the fall injury rate. Phase 2: There were 1502 fall injuries and 648 spring injuries, with 192 attributable to the spring risk factor. There was a 3-fold increase in injury rate in the spring (incidence density ratio = 3.2). Although the noncontact, helmets-only practices produced the lowest injury rates, the nonspring game scrimmages and the limited-contact practices defined as "practice with pads but without tackling" displayed the highest injury rates. In both spring and fall, nonplayers exhibited the highest injury rates for all string groups.

CONCLUSIONS

There was and still is a statistically significant increase in spring practice injury risk. The 1998 rule change resulted in an even greater increase in spring practice injury risk. If the goal is to minimize the number of spring practice injuries, it will be best accomplished by limiting the number of scrimmages and limited-contact sessions.

Place des orthèses en pathologie ligamentaire du genou. Revue de la littérature

OBJECTIVE

To review the literature for the benefits of the three different knee braces (prophylactic, rehabilitation, functional) that can be used to treat ligament injuries of the knee. What is their influence on stability? Do they have adverse effects? Is their use justified?

METHODS

We searched the Medline and Embase databases with use of the keywords knee, orthoses, brace, proprioception, stability, rehabilitation, physical therapy, and anterior cruciate ligament for reports published between 1980 and 2003 and selected 93 articles, expert reports or literature reviews.

RESULTS

Anterior tibial displacement can be controlled with mechanical strains (150 N), which are lower than physiological restraints? (400 N). The control of joint position is improved by increasing proprioception. Soft tissue stiffness influences the control of anterior tibial displacement. The beneficial effects observed are mainly subjective. Our analysis of the literature showed limitations and variations in study methodologies.

CONCLUSION

We did not find any justification for use of either prophylactic or rehabilitation braces. Functional braces can improve stability, as reported by the patient, and may be used in some situations.

Anterior cruciate ligament injuries in the National Football League: epidemiology and current treatment trends among team physicians

PURPOSE

To review the epidemiology of anterior cruciate ligament (ACL) injuries in the National Football League (NFL) and current treatment trends within this population.

TYPE OF STUDY

Descriptive.

METHODS

Part 1 of this study reviews the data collected in the NFL Injury Surveillance System from 1986 to 1995 with respect to these injuries. Included in this review are the specifics surrounding these injuries such as exposure type (game versus practice), position, mechanism, and playing surface on which the injury occurred. Part 2 of this analysis focuses on present treatment performed on these high-level athletes through a survey that was sent to and completed by all 31 NFL team orthopaedic surgeons.

RESULTS

The total number of ACL injuries in this select population has remained constant over the period analyzed.

CONCLUSIONS

Current preferred treatment technique favors endoscopic patellar tendon autograft reconstruction.

Long-term metabolic and skeletal muscle adaptations to short-sprint training: implications for sprint training and tapering

The adaptations of muscle to sprint training can be separated into metabolic and morphological changes. Enzyme adaptations represent a major metabolic adaptation to sprint training, with the enzymes of all three energy systems showing signs of adaptation to training and some evidence of a return to baseline levels with detraining. Myokinase and creatine phosphokinase have shown small increases as a result of short-sprint training in some studies and elite sprinters appear better able to rapidly breakdown phosphocreatine (PCr) than the sub-elite. No changes in these enzyme levels have been reported as a result of detraining. Similarly, glycolytic enzyme activity (notably lactate dehydrogenase, phosphofructokinase and glycogen phosphorylase) has been shown to increase after training consisting of either long (>10-second) or short (<10-second) sprints. Evidence suggests that these enzymes return to pre-training levels after somewhere between 7 weeks and 6 months of detraining. Mitochondrial enzyme activity also increases after sprint training, particularly when long sprints or short recovery between short sprints are used as the training stimulus. Morphological adaptations to sprint training include changes in muscle fibre type, sarcoplasmic reticulum, and fibre cross-sectional area. An appropriate sprint training programme could be expected to induce a shift toward type IIa muscle, increase muscle cross-sectional area and increase the sarcoplasmic reticulum volume to aid release of Ca(2+). Training volume and/or frequency of sprint training in excess of what is optimal for an individual, however, will induce a shift toward slower muscle contractile characteristics. In contrast, detraining appears to shift the contractile characteristics towards type IIb, although muscle atrophy is also likely to occur. Muscle conduction velocity appears to be a potential non-invasive method of monitoring contractile changes in response to sprint training and detraining. In summary, adaptation to sprint training is clearly dependent on the duration of sprinting, recovery between repetitions, total volume and frequency of training bouts. These variables have profound effects on the metabolic, structural and performance adaptations from a sprint-training programme and these changes take a considerable period of time to return to baseline after a period of detraining. However, the complexity of the interaction between the aforementioned variables and training adaptation combined with individual differences is clearly disruptive to the transfer of knowledge and advice from laboratory to coach to athlete.

[Knee orthosis. Evaluation of clinical efficiency with a review of the literature]

INTRODUCTION

The aim of this work was to collect literature data to assess the knee orthosis use with controlled clinical trials.

METHOD

The international literature relating to the years 1980-2000 was carried out with the Medline data bank.

RESULTS

Five hundred and twelve articles were collected and 35 were retained, 32 related to clinical studies and three related to toxicity. The evaluations were performed with either functional tests or clinical studies. The open-non controlled clinical trials are far higher than prospective comparative clinical trials that were developed only during last years. Main criteria of judgement are articular stability, functional pain and clinical index. Most of studies focused the anterior cruciate ligament lesions, patellar pains and osteoarthritis.

DISCUSSION

This review of the literature may help to determine the interest and the limits of orthosis use as well as side effect occurrence. Both these clinical and experimental data point out the methodological difficulties facing the investigatory clinician in knee orthosis evaluation.

CONCLUSION

Many studies contributed to the clinical evaluation of the knee orthosis. This work highlights various clinical indications for the same orthosis and variable results for the same indication. These methodological difficulties may not prevent a further evaluation of these devices to improve their use in current practice.

Effects of protective knee bracing on speed and agility

We evaluated the effects of prophylactic knee braces on athlete speed and agility, as well as brace tendency to migrate. Thirty college football players in full gear ran a 40-yard dash and a four-cone agility drill wearing braces on both knees or no brace (control). Braces included the DonJoy Legend, Breg Tradition, OMNI-AKS 101W, McDavid Knee Guard, and models 1 and 2 of the Air Armor Knee and Thigh Protection System. Brace migration and subjective measures were recorded after each trial. In the 40-yard dash, times using Air Armor 1 and OMNI did not differ significantly from control. Times with other braces were significantly slower. In the four-cone drill, only the Breg times were significantly slower than control. The Air Armor 1 and McDavid braces showed significantly less superior/inferior migration in the 40-yard dash than other braces. In the four-cone drill, the Air Armor 1 and 2 showed significantly less superior/inferior migration than other braces. These findings indicate that selected knee braces do not significantly reduce speed or agility. Braces showed a variable tendency to migrate, which could affect their protective function and athlete performance. This information will help athletes and coaches decide about knee-brace use during sports; studies are needed regarding whether braces protect against knee injury. This study does not constitute an endorsement of knee-brace use or efficacy.

Musculoskeletal rehabilitation and sports medicine. 3. Knee and lower extremity injuries

This self-directed learning module discusses classic concepts and highlights new advances in the diagnosis and management of knee and lower extremity injuries that commonly occur during athletic competition. It is part of the chapter on musculoskeletal rehabilitation and sports medicine in the Self-Directed Physiatric Education Program for practitioners and trainees in physical medicine and rehabilitation.

Common athletic knee injuries

Knee injuries continue to be an increasingly common and highly visible problem presenting to the sports medicine physician. The physicians who handle knee injuries will be challenged by patients, coaches, trainers, business agents, the press, and family members with an ever-increasing sophistication of medical knowledge. An understanding of the underlying structure and function of the commonly injured ligaments, menisci, and the patellofemoral joint is discussed. Diagnosis by physical examination is encouraged. Conservative and surgical treatment options are reviewed as are the considerations involved in deciding the time to return to sports.

Knee bracing: effects of proprioception

OBJECTIVE

To examine the effects of a knee sleeve type brace on the proprioceptive ability of subjects with normal knees during a dynamic tracking task.

DESIGN

A 2 X 2 Latin square cross over design; in each Latin square, subjects were matched for age and gender.

SETTING

An institution focused on clinical education.

PARTICIPANTS

Twenty subjects with no musculoskeletal or neurological conditions.

INTERVENTIONS

Each subject performed a tracking task on a Kin-Com dynamometer. Angle and force data from the Kin-Com and angle data from an electrogoniometer were sampled at 100Hz using a data acquisition program on a PC computer. The subjects were blindfolded and the limb attached to the Kin-Com was moved passively by the dynamometer. Subjects were instructed to follow the movement as closely as possible with the other limb (the tracking limb). Subject performed two trials, one without knee bracing and another that involved the application of a brace to the tracking limb.

OUTCOME MEASURE

The magnitude of the error in tracking was established by taking the difference of the active and passively moving limbs and calculating the root mean square (RMS) of the difference.

RESULTS

The findings showed that there was an improvement of 11% in tracking when subjects wore the knee brace (p < .05).

CONCLUSION

Alterations in proprioception as a result of bracing may be partly responsible for the improvement in knee injury statistics reported in some studies.

Use of knee braces in sport. Current recommendations

This article provides a review of the progress that has been made on the biomechanical, functional performance and epidemiological investigations into the effectiveness of prophylactic knee braces (PKBs) since the position statement against their use was issued in 1987 by the American Academy of Orthopaedics and a review of this subject was last published in Sports Medicine in 1989 by Montgomery and Korziris. The evolution of the salient design features of three surrogate knee models are reviewed along with the results of PKB effectiveness and safety factor testing. While still too limited in scope to be totally realistic, major advances have been made in the sophistication of the present biomechanics laboratory testing conditions. The on-the-field functional performance effects of wearing a knee brace are not always manifest in all individuals. The efficacy of PKBs remains in question but recent studies have taught us enough to put their use into perspective. While they may play some role, PKBs probably represent the least important factor in influencing the likelihood that a medial collateral ligament (MCL) sprain will occur. On the other hand, there is no evidence that such braces put added valgus pressure on some knees, or that wearing a brace is associated with an increased frequency or severity of knee or ankle injury. All else being equal, from the biomechanical studies, we know that whilst some braces are better than others, currently available PKBs can provide 20 to 30% greater resistance to a lateral blow, with the possibility that the anterior cruciate ligament (ACL) is given even greater protection than the MCL. This appears to be true when the lateral blow is of sufficient magnitude to cause significant medial joint line opening, but is not as great at the very lowest levels of impact. Regardless of the material they are made of, the most effective PKBs are those sufficiently stiff to prevent an external blow at the joint line from causing brace hinge contact with the knee tissues. Based on the superior results of the custom-fit functional braces, the most important future design feature appears to be the sizing and fitting of the thigh and tibial cuffs. On the negative side, the presence of a brace may slow an athlete's straight-ahead sprint speed and cause early fatigue to its wearer. This effect appears to vary from one brace to another according to its weight, design features, and pressure from the leg and thigh straps. However, it appears that knee braces do have the potential to restrict performance of the athlete for high-speed running but the effect is related to several factors. The weight of the brace resultant friction of the hinges, completeness of fit, and tightness of straps appear to be important. The most measurable effects include: increased muscular relaxation pressures; increased energy expenditure; and a related increase in blood lactate levels, maximal torque output, oxygen consumption and heart rate. On the other hand, experienced brace wearers and larger, stronger individuals displayed fewer, or no effects of donning a brace. Improvements in the protectiveness of the PKB are likely to accompany improvements in the ability to contour the braces to fit each individual's leg in the equipment room without the added expense of the cast-moulding process. Further improvement may be realised by friction-free polycentric joints, as well as an attachment system that minimises thigh and calf soft tissue compression perhaps by incorporating the braces into the trousers of the uniform to provide suspension from the waist.