Overview of injuries in the young athlete

It is estimated that 30 million children in the US participate in organised sports programmes. As more and more children participate in sports and recreational activities, there has been an increase in acute and overuse injuries. Emergency department visits are highest among the school-age to young adult population. Over one-third of school-age children will sustain an injury severe enough to be treated by a doctor or nurse. The yearly costs have been estimated to be as high as 1.8 billion US dollars. There are physical and physiological differences between children and adults that may cause children to be more vulnerable to injury. Factors that contribute to this difference in vulnerability include: children have a larger surface area to mass ratio, children have larger heads proportionately, children may be too small for protective equipment, growing cartilage may be more vulnerable to stresses and children may not have the complex motor skills needed for certain sports until after puberty. The most commonly injured areas of the body include the ankle and knee followed by the hand, wrist, elbow, shin and calf, head, neck and clavicle. Contusions and strains are the most common injuries sustained by young athletes. In early adolescence, apophysitis or strains at the apophyses are common. The most common sites are at the knee (Osgood-Schlatter disease), at the heel (Sever's disease) and at the elbow (Little League Elbow). Non-traumatic knee pain is one of the most common complaints in the young athlete. Patellar Femoral Pain Syndrome (PFPS) has a constellation of causes that include overuse, poor tracking of the patellar, malalignment problems of the legs and foot problems, such as pes planus. In the child, hip pathology can present as knee pain so a careful hip exam is important in the child presenting with an insidious onset of knee pain. Other common injuries in young athletes discussed include anterior cruciate ligament injuries, ankle sprains and ankle fractures. Prevention of sports and recreation-related injuries is the ideal. There are six potential ways to prevent injuries in general: (i) the pre-season physical examination; (ii) medical coverage at sporting events; (iii) proper coaching; (iv) adequate hydration; (v) proper officiating; and (vi) proper equipment and field/surface playing conditions.

Effect of functional bracing on subsequent knee injury in ACL-deficient professional skiers

The effect of functional bracing on subsequent knee injury in anterior cruciate ligament (ACL) deficient professional skiers was evaluated. A cohort of 180 ACL-deficient skiers was identified from a knee screening of 9410 professional skiers from 1991-1997. An ACL-deficient knee was defined by an abnormal examination (Lachman or pivot-shift) and a > or = 5-mm KT-1000 manual maximum difference. The dependent variable was subsequent knee injury, which occurred in 12 knees. A significantly higher proportion of injuries occurred in nonbraced skiers compared with braced skiers (P = .005). The risk ratio for subsequent knee injury comparing nonbraced with braced skiers was 6.4 (13% and 2%, respectively). Univariate analysis revealed no significant effects of the other covariates. Logistic regression identified bracing status (P < .01; odds ratio = 8) and KT-1000 manual maximum difference (P = .02; odds ratio = 1.3) as significant multivariate risk factors for subsequent knee injury, controlling for covariates.

Prevention of anterior cruciate ligament injuries in female team handball players: a prospective intervention study over three seasons

OBJECTIVE

To assess the effect of a neuromuscular training program on the incidence of anterior cruciate ligament injuries in female team handball players.

DESIGN

Prospective intervention study.

SETTING

Female team handball: Division I-III in Norway.

PARTICIPANTS

Players from the three top divisions: control season (1998-1999), 60 teams (942 players); first intervention season (1999-2000), 58 teams (855 players); second intervention season (2000-2001), 52 teams (850 players).

INTERVENTION

A five-phase program (duration, 15 min) with three different balance exercises focusing on neuromuscular control and planting/landing skills was developed and introduced to the players in the autumn of 1999 and revised before the start of the season in 2000. The teams were instructed in the program and supplied with an instructional video, poster, six balance mats, and six wobble boards. Additionally, a physical therapist was attached to each team to follow up with the intervention program during the second intervention period.

MAIN OUTCOME MEASURES

The number of anterior cruciate ligament injuries during the three seasons and compliance with the program.

RESULTS

There were 29 anterior cruciate ligament injuries during the control season, 23 injuries during the first intervention season (OR, 0.87; CI, 0.50-1.52; p = 0.62), and 17 injuries during the second intervention season (OR, 0.64; CI, 0.35-1.18; p = 0.15). In the elite division, there were 13 injuries during the control season, six injuries during the first intervention season (OR, 0.51; CI, 0.19-1.35; p = 0.17), and five injuries in the second intervention season (OR, 0.37; CI, 0.13-1.05; p = 0.06). For the entire cohort, there was no difference in injury rates during the second intervention season between those who complied and those who did not comply (OR, 0.52; CI, 0.15-1.82; p = 0.31). In the elite division, the risk of injury was reduced among those who completed the anterior cruciate ligament injury prevention program (OR, 0.06; CI, 0.01-0.54; p = 0.01) compared with those who did not.

CONCLUSIONS

This study shows that it is possible to prevent anterior cruciate ligament injuries with specific neuromuscular training.

Optimal entry point for retrograde femoral nailing

OBJECTIVE

The purpose of this study is to identify the optimum entry point for retrograde femoral nailing, defined as that point which will provide adequate fracture alignment while minimizing soft-tissue and articular cartilage injury.

DESIGN

Cadaveric study.

SETTING

Biomechanics laboratory.

MAIN OUTCOME MEASURE

Anatomic relationships and fracture reduction. METHODS Eleven cadaveric femori with attached knee joints underwent retrograde femoral nailing with a Synthes femoral nail (Synthes, Paoli, PA, U.S.A.). After placement of the nail, the specimens underwent an osteotomy 3 inches proximal to the articular surface. Multiple entry points were tested to determine fracture alignment and extent of articular cartilage injury. Medial-lateral and anterior-posterior displacements, in addition to any soft-tissue or articular surface trauma, were recorded for these various points of entry.

RESULTS

An entry point of 1.2 cm anterior to the femoral origin of the posterior cruciate ligament resulted in the least anterior-posterior displacement of the femoral shaft following fracture. In the coronal plane, an entry point at the midpoint of the intercondylar sulcus was identified as minimizing the displacement following fracture. This ideal position allows for proper seating of the nail within the intercondylar sulcus, resulting in minimal damage to the articular cartilage and posterior cruciate ligament and minimal disruption of the patella femoral joint.

CONCLUSION

Retrograde femoral nailing should be used cautiously in select patients, when conventional antegrade nailing cannot be used, due to the unavoidable injury to the knee articular surface associated with this technique. The optimum entry point of 1.2 cm anterior to the femoral posterior cruciate ligament origin and centered in the intercondylar sulcus provides the optimal balance of fracture reduction and knee joint sparing. It may be difficult to target this site with a percutaneous technique and may require direct visualization of the intercondylar sulcus for ideal nail placement.

The skier's knee

Knee injuries in skiers have unique epidemiology and distinct mechanisms. Conversely, evaluation and treatment of the skier's knee is similar to evaluation and treatment of knee injuries in other athletes. A greater understanding of the epidemiology and mechanisms of knee injuries in skiers may aid arthroscopic clinicians and related researchers treating or investigating knee injuries in both skiers and in other athletes.

Alpine ski injuries and their prevention

Alpine skiing is a popular sport with significant risk of injury. Since the 1970s, injury rates have dropped from approximately 5 to 8 per 1000 skier-days to about 2 to 3 per 1000 skier-days. The nature of the injuries has also been transformed over the same period. Lower leg injuries are becoming less common while the incidence of knee sprains and upper extremity injuries is becoming more common. Much of this change can be attributed to advancements in binding technology, which effectively reduces lower leg injury, but does not adequately address the issue of knee sprains. Along with design, binding adjustment and maintenance are important preventative factors. Poorly adjusted bindings have been correlated with increased injury rates. Upper extremity injuries constitute approximately one-third of skiing injuries, with ulnar collateral ligament sprains and shoulder injuries being the most common. Strategies to prevent these include proper poling technique and avoidance of non-detachable ski pole retention devices. Spinal injuries in skiers have been traditionally much less common than in snowboarders, but this disparity is likely to diminish with the recent trend of incorporating snowboarding moves into skiing. Strategies to help reduce these injuries include promoting the development of terrain parks and focussing on proper technique during such moves. Head injuries have been increasing in incidence over recent decades and account for more than half of skiing-related deaths. The issue of ski helmets remains controversial while evidence for their efficacy remains under debate. There is no evidence to demonstrate that traditional ski instruction reduces injury frequency. More specific programmes focussed on injury prevention techniques are effective. The question of pre-season conditioning to prevent injuries needs further research to demonstrate efficacy.

The female ACL: why is it more prone to injury?

Multiple factors are responsible for ACL tears. The key factor in the gender discrepancy appears to be dynamic, not static, and proximal, not distal. The factors involved in evaluating the female ACL are multiple. However, it is the dynamic movement patterns ot hip and knee position with increased flexion and a coordinated proximal muscle firing pattern to keep the body in a safe landing position that are the most critical factors. An ACL injury at an early age is a life-changing event. We can very successfully reconstruct and rehabilitate an ACL, but we cannot stop there. We must now go into the prevention arena. In the United States there is tremendous variation in the exposure and acquisition of skills of physical activities in our youth. Today, children are often playing inside, using computers and watching television-missing out on the opportunity to learn safe movement patterns. Therefore, physical movement classes should occur very early in life, teaching children to land safely and in control, similar to the cry of "get down, stay down" routinely heard during youth soccer. Similarly, specific strength training programs can address landing as well as foot movements during cutting in basketball. Coaches should issue stern warnings when athletes demonstrate a high-risk movement patterns such as one-leg landings, out-of-control baseline landings, or straight-leg landings. The warnings may serve to keep the athlete from "touching the hot stove again" for fear of getting burned. No athlete feels she will be the one to get injured. Therefore, prospective analysis is likely to be received more warmly by the athletes if the program is presented with an emphasis on performance improvement rather than injury prevention. With increased participation in these programs, multiple-center analysis will have the power necessary to determine which factors significantly predispose athletes to ACL injury. The future for injury prevention is bright. We must rise to the challenge.

Lower limb taping

This article, the final in this series, describes taping techniques for common lower limb problems. Taping can be used to correct abnormal biomechanics (e.g. patellofemoral pain), prevent recurrent injury (e.g. ankle taping for instability), offload the injured tissue (e.g. acute ankle sprain) or provide proprioception awareness (e.g. Achilles tendonitis).

Injury surveillance and systematic investigation identify a rubber matting hazard for anterior cruciate ligament rupture on an obstacle course

In June 1998, six unexpected anterior cruciate ligament ruptures within 12 months were detected by routine injury surveillance in a cohort of Australian Army recruits. A systematic investigative process was used to identify the probable cause. Review of the case histories, followed by on-site assessment of the common hazard, revealed that all ruptures occurred as recruits twisted or landed on newly laid rubber matting at one obstacle course. The matting was laid with the intention of countering ground wear, shock of impact, and slipping to reduce the risks of ankle sprain and stress fracture. Review of the literature indicated that the interface between the rubber boot sole and rubber matting was associated with a very high coefficient of friction, probably causing excessive torque at the knee. Similar mechanisms of anterior cruciate ligament injury have been reported in sports and skiing. A subsequent study of intervention effects, reported separately in this issue, was conducted to confirm the damaging role of the matting. Routine injury surveillance and systematic investigation are valuable tools for injury prevention. Clinicians are well equipped for both.

Anterior cruciate ligament injuries in the female athlete

With the participation of women in athletics growing rapidly over the last two decades, a disturbing gender-specific pre-disposition has emerged regarding anterior cruciate ligament (ACL) injuries of the knee. Female athletes have a two- to eightfold higher incidence of ACL injury than their male counterparts. It is estimated that 38,000 women sustain ACL tears per year. The majority of ACL injuries in female athletes occur through noncontact mechanisms, most often during deceleration activities, such as landing from a jump or cutting. The risk factors for noncontact ACL injuries can be categorized as intrinsic (anatomic and hormonal) and extrinsic (environmental and biomechanical). This article will discuss these risk factors that are thought to contribute to the higher incidence of ACL injuries in women, the development of prevention strategies, and the outcomes of ACL reconstruction in women.

Neuromuscular contributions to anterior cruciate ligament injuries in females

Although anterior cruciate ligament (ACL) injuries are not gender specific, they do occur at a significantly greater rate in females. Biomechanical and neuromuscular deficits in females have been documented as factors contributing to ACL injuries, however little research has been conducted in the area of preventative training programs to improve these deficits. This article will describe the biomechanical and neuromuscular factors that contribute to ACL injuries in females, and provide a foundation from which preventative training programs should be designed.

[Evaluation of mechanical and neurophysiological effects of wearing bandages for the knee joint in functional testing situations]

The purpose of the study was to estimate the stabilising effects of two functional bandages for the knee joint. Two mechanisms typically leading to knee injuries were simulated. Three-dimensional recordings of knee joint angles and recordings of the tibial displacement in anterior-posterior direction were used to determine the destabilisation of the knee joint as a result of the applied mechanical stimuli, as well as the stabilising support of wearing the bandages. Reflex activations of the knee joint muscles and their modulation by the bandages were measured by EMG. To estimate limitations of the sports performance by the bandages, the subjects performed an additional test for postural stability. The testing performance, the three-dimensional knee joint angles and muscle activities were measured. While the FUTURO(R)-knee joint bandage (BDF AG) caused both mechanical and neurophysiological effects, the action of the KASSELER bandage (Sporlastic(R) GmbH) relied solely on the enhancement of muscular activities. The applied methods proved to be a very useful tool for the evaluation of stabilising effects of bandages in functional situations.

Prevention of anterior cruciate ligament injuries

Numerous studies have found that female athletes who participate in jumping and pivoting sports are four to six times more likely to sustain a knee ligament injury, such as anterior cruciate ligament (ACL) injury, than male athletes participating in the same sports [1-8]. A widening gender gap in the number of serious knee ligament injuries exists due to geometric growth in female athletic participation, coupled with the four- to sixfold higher injury rate. More than 50,000 serious knee injuries are projected to occur in female varsity intercollegiate and high school athletics each year [9, 10]. Most ACL injuries occur by noncontact mechanisms, often during landing from a jump or making a lateral pivot while running [2, 11]. Knee instability, due to ligament dominance (decreased medial-lateral neuromuscular control of the joint), quadriceps dominance (increased quadriceps recruitment and decreased hamstring recruitment and strength), and leg dominance (side-to-side differences in strength, flexibility, and coordination) are possible contributing factors to the increased incidence of knee injury in female athletes [5, 6]. In this review, dynamic neuromuscular analysis (DNA) training is defined, and a rationale is presented for correcting the neuromuscular imbalances that may result in dynamic knee instability during sports play. Dynamic neuromuscular training has been shown to increase knee stability and decrease knee injury rates in female athletes [5, 12.., 13.]. Preliminary research on athlete screening and injury prediction based on the three aforementioned imbalances also is presented with recommendations for developing screening protocols for the identification of high-risk athletes.

Proprioceptive training and prevention of anterior cruciate ligament injuries in soccer

This commentary describes a program developed to help reduce the incidence of anterior cruciate ligament injuries in soccer players. The basic principles underlying the injury prevention protocol are described with respect to the proprioceptive control mechanisms at the knee joint. This is followed by a detailed description of the program.

Dynamic knee stability: current theory and implications for clinicians and scientists

We will discuss the mechanisms by which dynamic knee stability may be achieved and relate this to issues that interest clinicians and scientists concerned with dynamic knee stability. Emphasis is placed on the neurophysiologic evidence and theory related to neuromuscular control. Specific topics discussed include the ensemble firing of peripheral mechanoreceptors, the potential for muscle stiffness modulation via force and length feedback, postural control synergies, motor programs, and the neural control of gait. Factors related to answering the difficult question of whether or not knee ligament injuries can be prevented during athletic activities are discussed. Prevention programs that train athletes to perform their sport skills in a safe fashion are put forth as the most promising prospect for injury prevention. Methods of assessing neuromuscular function are reviewed critically and the need for future research in this area is emphasized. We conclude with a brief review of the literature regarding neuromuscular training programs.

[The application of external knee stabilizers - Influence on mechanical stabilization and physical performance]

The aim of the study was, to assess the influence of a knee brace on the development of anterior instability after anterior cruciate ligament rupture and to test aptitude for physical strain. 46 subjects with arthroscopically proven anterior cruciate ligament rupture were divided equally in a randomised order into two groups. Both groups carried out a standardized physical therapy program, while one group (0) received additional stabilization by means of a functional knee brace (SofTec, Bauerfeind). In addition, important features of the brace (stabilization capacity, safety perception and physical performance) were tested and compared to the non-braced contralateral leg among 23 healthy physical education students by means of a standardized scaled questionnaire (observational study). 0 showed lower (p < 0.05) development of the anterior instability by 46 % and lower (p < 0.05) reduction in circumference of the femur muscles by 25 %. Increasing the time interval between accident and beginning of the brace treatment, increased the difference of the therapeutical effect of the brace. In the observational study, the brace received a better evaluation regarding all test parameters. The reduction of developing anterior instability by means of a brace should facilitate - apart from an individual operation-time-arrangement - especially a conservative approach within the framework of anterior instability and physical activity. Aside from the improvement of the mechanical stabilization, indications for suitability in strain situations could be detected for the tested brace.

American Academy of Pediatrics: Technical report: knee brace use in the young athlete

This statement is a revision of a previous statement on prophylactic knee bracing and provides information for pediatricians regarding the use of various types of knee braces, indications for the use of knee braces, and the background knowledge necessary to prescribe the use of knee braces for children.

Impact responses of the flexed human knee using a deformable impact interface

Blunt impact trauma to the patellofemoral joint during car accidents, sporting activities, and falls can produce a range of injuries to the knee joint, including gross bone fracture, soft tissue injury, and/or microinjuries to bone and soft tissue. Currently, the only well-established knee injury criterion applies to knee impacts suffered during car accidents. This criterion is based solely on the peak impact load delivered to seated cadavers having a single knee flexion angle. More recent studies, however, suggest that the injury potential, its location, and the characteristics of the damage are also a function of knee flexion angle and the stiffness of the impacting structure. For example, at low flexion angles, fractures of the distal patella are common with a rigid impact interface, while at high flexion angles splitting of the femoral condyles is more evident. Low stiffness impact surfaces have been previously shown to distribute impact loads over the anterior surface of the patella to help mitigate gross and microscopic injuries in the 90 deg flexed knee. The objective of the current study was to determine if a deformable impact interface would just as effectively mitigate gross and microscopic injuries to the knee at various flexion angles. Paired experiments were conducted on contralateral knees of 18 human cadavers at three flexion angles (60, 90, 120 deg). One knee was subjected to a fracture level impact experiment with a rigid impactor, and the opposite knee was impacted with a deformable interface (3.3 MPa crush strength honeycomb material) to the same load. This (deformable) impact interface was effective at mitigating gross bone fractures at approximately 5 kN at all flexion angles, but the frequency of split fracture of the femoral condyles may not have been significantly reduced at 120 deg flexion. On the other hand, this deformable interface was not effective in mitigating microscopic injuries observed for all knee flexion angles. These new data, in concert with the existing literature, suggest the chosen impact interface was not optimal for knee injury protection in that fracture and other minor injuries were still produced. For example, in 18 cadavers a total of 20 gross fractures and 20 subfracture injuries were produced with a rigid interface and 5 gross fractures and 21 subfracture injuries with the deformable interface selected for the current study. Additional studies will be needed to optimize the knee impact interface for protection against gross and microscopic injuries to the knee.

Contributions of proximal and distal moments to axial tibial rotation during walking and running

The purpose of this study was to determine the cause and effect relationship between tibial internal rotation and pronation of the foot during walking and heel-toe running. This would allow predictions of orthotic effectiveness in reducing knee pain related to excessive internal tibial rotation. Kinematic and force plate data were collected from twenty subjects performing ten running and ten walking trials across a force plate. Using a least-squares algorithm, attitude matrices for each segment in each frame were obtained and the angular velocity vector of the tibia was calculated. The intersegmental moment at the ankle was calculated from ground reaction force and kinematic data, and the power flow from foot to tibia associated with axial tibial rotation was calculated. In walking, all subjects exhibited a clear power flow from tibia to foot during most of the stance phase, indicating that the foot was following the body. This suggests that the use of foot orthoses to reduce knee pain associated with tibial rotation during walking will not be successful. During running, power flow was also mainly proximal to distal, but there were brief periods of opposite power flow. There was more variability between subjects during running, with five subjects having large distal to proximal power flow peaks. These observations may explain and support previous work that has found variable clinical effects of orthoses between patients.

[Risk factors in leisure sports. Early and late sequelae]

Risk factors for sports injuries result from extrinsic factors such as footgear, playing field surfaces, and crash helmets as well as intrinsic factors such as muscle imbalances, chronic injuries, and deficiencies in coordination. To prevent sports injuries, the incidence and severity of sports injuries must be identified and described. Then the mechanisms of injury and the risk factors must be determined accordingly. Only thereafter can consideration be given to measures that reduce the risk and severity of sports injuries. To be able to conclusively establish the total benefit of preventive measures, this process must be continually monitored for its efficacy.

The influence of functional knee bracing on the anterior cruciate ligament strain biomechanics in weightbearing and nonweightbearing knees

Functional knee braces are commonly prescribed after anterior cruciate ligament injury or reconstruction; however, their ability to protect the ligament, or graft, remains unclear. Our objective was to evaluate the anterior cruciate ligament strain response in braced and unbraced knees during weightbearing and nonweightbearing in combination with three externally applied loads: 1) anterior-posterior shear forces, 2) internal-external torques, and 3) varus-valgus moments. The Legend brace was tested. All external loads were applied to the tibia with the knee flexed to 20 degrees. Reproducible data were obtained from 11 subjects. For anterior shear loads up to 130 N, the brace significantly reduced strain values compared with the unbraced knee during nonweightbearing and weightbearing conditions. For internal torques of the tibia (up to 9 N x m), strain in the braced knee was significantly less than in the unbraced knee when the knee was nonweightbearing only. The brace did not reduce strain values when the knee was subjected to external torques (9 N x m) or varus-valgus moments (10 N x m) in weightbearing and nonweightbearing knees. These data indicate that a functional knee brace can protect the anterior cruciate ligament during anterior-posterior shear loading in the nonweightbearing and weightbearing knee and during internal torques in the nonweightbearing knee.

The sliding stop: a technique of fielding in cricket with a potential for serious knee injury

The sliding stop method of fielding in cricket is gaining popularity in schools and club cricket through its frequent exposure on television. The case history is reported of a cricketer who suffered a torn medial meniscus in his knee, a rare cricketing injury, while performing this technique incorrectly in a club game. The correct method of performing the technique is described in coaching manuals but is not commonly instructed at club or school level. The sliding stop should be discouraged in school and for club cricketers unless appropriately coached.

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.

Neuromuscular and hormonal factors associated with knee injuries in female athletes. Strategies for intervention

Female athletes who participate in jumping and cutting sports are 4 to 6 times more likely to sustain a serious knee injury than male athletes participating in the same sports. More than 30,000 serious knee injuries are projected to occur in female intercollegiate and high school athletics in the US each year. The majority of these injuries occur by non-contact mechanisms, most often during landing from a jump or making a lateral pivot while running. Knee instability, due possibly to decreased neuromuscular strength and coordination or increased ligamentous laxity, may underlie the increased incidence of knee injury in females. Neuromuscular training can significantly increase dynamic knee stability in female athletes. Female sex hormones (i.e. estrogen, progesterone and relaxin) fluctuate radically during the menstrual cycle and are reported to increase ligamentous laxity and decrease neuromuscular performance and, thus, are a possible cause of decreases in both passive and active knee stability in female athletes. Oral contraceptives stabilise hormone levels during the menstrual cycle and may function to either passively or actively stabilise the knee joint. The long term objective of clinicians and researchers should be to determine the factors that make women more susceptible than men to knee ligament injury and to develop treatment modalities to aid in the prevention of these injuries. The immediate objectives of this review are to examine how female and male athletes differ in neuromuscular and ligamentous control of the lower extremity. The review will examine the effects of neuromuscular training on knee stability. The effects of female hormone levels and oral contraceptives on neuromuscular control of the female athletes' knee will also be discussed.

Noncontact anterior cruciate ligament injuries: risk factors and prevention strategies

An estimated 80,000 anterior cruciate ligament (ACL) tears occur annually in the United States. The highest incidence is in individuals 15 to 25 years old who participate in pivoting sports. With an estimated cost for these injuries of almost a billion dollars per year, the ability to identify risk factors and develop prevention strategies has widespread health and fiscal importance. Seventy percent of ACL injuries occur in noncontact situations. The risk factors for non-contact ACL injuries fall into four distinct categories: environmental, anatomic, hormonal, and biomechanical. Early data on existing neuromuscular training programs suggest that enhancing body control may decrease ACL injuries in women. Further investigation is needed prior to instituting prevention programs related to the other risk factors.

Case-control study of discharge from the U.S. Army for disabling occupational knee injury: the role of gender, race/ethnicity, and age

BACKGROUND

Occupational injuries are responsible for more lost time from work, productivity, and working years of life than any other health condition in either civilian or noncombat military sectors. Injuries, not illnesses, are the leading cause of morbidity and mortality among U.S. Army personnel. We examined the separate and joint roles of gender, race/ethnicity, and age in the odds of discharge from the Army for disabling knee injury.

METHODS

A total of 860 women and 7868 men were discharged from the Army between 1980 and 1995 for knee-related disability and met all inclusion criteria for this study. All women and a subsample of 1005 men were included in these analyses, along with a simple random sample of three controls per case, stratified by gender, drawn from the population of all active-duty enlisted soldiers in each year from 1980 to 1995. We identified predictors of the occurrence or nonoccurrence of discharge from the Army for disabling knee injury using unconditional multiple logistic regression analyses.

RESULTS

We found relations between the risk of knee-related disability and age and race, with marked effect modification by gender. Non-Caucasian men and women were at lower risk than Caucasians at all ages. At most ages, Caucasian women were at higher risk than Caucasian men, and non-Caucasian women were at lower risk than non-Caucasian men. Within race/ethnicity and gender, the risks for men showed an inverted "U" shape with increasing age, and the risks for women showed a "J" shape with increasing age.

CONCLUSIONS

Age, race/ethnicity, and gender interactions are important in occupational injury. Differences in risk may be related to differences in work assignments, leisure activities, physical or physiological differences, or the ways in which disability compensation is granted.

Motor pattern of the knee joint muscles during side-step cutting in European team handball. Influence on muscular co-ordination after an intervention study

The incidence of anterior cruciate ligament (ACL) injuries is reported to be high in many popular team sports The most risky movement in European team handball is reported to be the side-step cutting manoeuvre. Well-rehabilitated ACL-deficient athletes have been shown to have increased co-contraction about the knee joint with this manoeuvre. The aim of this study was to examine the effect of a prophylactic training programme on the co-contraction of the knee joints of non-injured European team handball players The subjects performed 'match-like' cutting manoeuvres on a force platform. EMG-signals from the involved knee joint muscles and force platform signals were simultaneously stored on a personal computer. The data collected before and after a 12-week prophylactic training program were compared. The results demonstrated that rehabilitation exercises cannot increase co-contraction about the knee joint in healthy athletes during side-step cutting. This is contradictory to the reported effect on ACL-deficient athletes.

The anterior cruciate ligament enigma. Injury mechanisms and prevention

The reasons for the higher frequency of anterior cruciate ligament injuries in women are largely conjecture. These injuries may result from direct contact or, more frequently, from no direct contact to the knee during activities that most athletes consider routine to their sport. This implies that there are intrinsic factors that lead to anterior cruciate ligament rupture. For the anterior cruciate ligament to tear, there must be excess anterior tibial translation or rotation of the femur on the tibia. In the former case, the tibia can move anteriorly during quadriceps activation that is not counterbalanced by hamstring activation. Patients describe their injury as occurring when landing, stopping, or when planting to change directions. The knee typically was near full extension. Mechanically, the angle of the patellar tendon and tibial shaft increases as the knee approaches full extension. This gives a mechanical advantage to the quadriceps. During cutting maneuvers, athletes tend to cut with a knee near extension (0 degree-20 degrees) when the quadriceps are active and the hamstrings are neither very active nor at a knee flexion angle that offers much of a mechanical advantage. In performing cutting and landing maneuvers, women tend to perform the activities more erect; that is, with their knee and hips closer to extension. One possible factor to help reduce the frequency of anterior cruciate ligament injuries in women may be in proper instruction for performing cutting and landing maneuvers which will lower their center of gravity thereby denying the quadriceps the opportunity to shift the tibia anteriorly.

Knee braces: current evidence and clinical recommendations for their use

Methods of preventing and treating knee injuries have changed with the rapid development and refinement of knee braces. Prophylactic knee braces are designed to protect uninjured knees from valgus stresses that could damage the medial collateral ligaments. However, no conclusive evidence supports their effectiveness, and they are not recommended for regular use. Functional knee braces are intended to stabilize knees during rotational and anteroposterior forces. They offer a useful adjunct to the treatment and rehabilitation of ligamentous knee injuries. Patellofemoral knee braces have been used to treat anterior knee disorders and offer moderate subjective improvement without significant disadvantages. Additional well-designed studies are needed to demonstrate objectively the benefits of all knee braces. Knee braces should be used in conjunction with a rehabilitation program that incorporates strength training, flexibility, activity modification and technique refinement.

The effect of neuromuscular training on the incidence of knee injury in female athletes. A prospective study

To prospectively evaluate the effect of neuromuscular training on the incidence of knee injury in female athletes, we monitored two groups of female athletes, one trained before sports participation and the other not trained, and a group of untrained male athletes throughout the high school soccer, volleyball, and basketball seasons. Weekly reports included the number of practice and competition exposures and mechanism of injury. There were 14 serious knee injuries in the 1263 athletes tracked through the study. Ten of 463 untrained female athletes sustained serious knee injuries (8 noncontact), 2 of 366 trained female athletes sustained serious knee injuries (0 noncontact), and 2 of 434 male athletes sustained serious knee injuries (1 noncontact). The knee injury incidence per 1000 athlete-exposures was 0.43 in untrained female athletes, 0.12 in trained female athletes, and 0.09 in male athletes (P = 0.02, chi-square analysis). Untrained female athletes had a 3.6 times higher incidence of knee injury than trained female athletes (P = 0.05) and 4.8 times higher than male athletes (P = 0.03). The incidence of knee injury in trained female athletes was not significantly different from that in untrained male athletes (P = 0.86). The difference in the incidence of noncontact injuries between the female groups was also significant (P = 0.01). This prospective study demonstrated a decreased incidence of knee injury in female athletes after a specific plyometric training program.

Preventing in-line skating injuries: how effective are the countermeasures?

There was a six-fold growth in participation in in-line skating in the US from 1989 to 1996 and a concomitant increase in injuries. Similar trends have been reported in Canada, the UK, Denmark and Australia. Falls, mostly from loss of balance, are a common cause of injury. Falling skaters typically put one or both hands out to break their fall and land on a hard surface with the upper limb sustaining the injury. Approximately one-quarter of all in-line skating injuries are wrist fractures. Hospital emergency department data shows that skaters aged 10 to 14 years are most at risk for injury. First-time skaters, inexperienced skaters and experienced skaters trying new tricks are also at risk for injury. In-line skating injuries can be severe, with several deaths reported. Measures to prevent in-line skating injury include: wearing personal protective equipment (wrist guards, helmets, knee and elbow pads); improving environmental conditions for skaters; providing lessons, particularly for novice skaters; certification for skating instructors; encouraging physical preparation; educating skaters about safety; improving equipment design and standards; and refining government policy and regulation in consultation with skating groups. Few of these measures have been formally proven to reduce injury. Controlled evaluations of the currently advocated methods are needed to establish their efficacy. More biomechanical and epidemiological research is needed, particularly in the area of wrist/forearm injury prevention. Given the rapid increase in popularity of in-line skating and the potential for a related epidemic of moderate to serious injuries, research into in-line skating injury prevention should be a priority.

Alpine ski bindings and injuries. Current findings

In spite of the fact that the overall incidence of alpine ski injuries has decreased during the last 25 years, the incidence of serious knee sprains usually involving the anterior cruciate ligament (ACL) has risen dramatically since the late 1970s. This trend runs counter to a dramatic reduction in lower leg injuries that began in the early 1970s and to date has lowered the risk of injury below the knee by almost 90%. One of the primary design objectives of modern ski boots and bindings has been to protect the skier from tibia and ankle fractures. So, in that sense, they have done an excellent job. However, despite advances in equipment design, modern ski bindings have not protected the knee from serious ligament trauma. At the present time, we are unaware of any binding design, settings or function that can protect both the knee and lower extremities from serious ligament sprains. No innovative change in binding design appears to be on the horizon that has the potential to reduce the risk of these severe knee injuries. Indeed, only 1 study has demonstrated a means to help reduce this risk of serious knee sprains, and this study involved education of skiers, not ski equipment. Despite the inability of bindings to reduce the risk of severe knee injuries there can be no doubt that improvement in ski bindings has been the most important factor in the marked reduction in incidence of lower leg and ankle injuries during the last 25 years. The authors strongly endorse the application of present International Standards Organisation (ISO) and American Society for Testing and Materials (ASTM) standards concerning mounting, setting and maintaining modern 'state of the art' bindings.

[To brace or not to brace? How effective are knee braces in rehabilitation?]

Since the clinical benefit of knee braces has yet to be defined, discussion about braces after reconstructive surgery of the anterior cruciate ligament remains controversial. The use of prophylactic braces in sport did not prove to be effective. In ACL insufficient knee joints, the operative treatment is preferred over the use of functional knee braces. Therefore, the postoperative rehabilitation presents the main application of braces. Modern operative techniques with an initial strong fixation of the ACL graft make a functional postoperative treatment without external fixation possible. In the presented meta-analysis of the literature about knee braces, results from clinical and experimental studies are compared. No published clinical data have shown that braces have any effect on postoperative outcome after ACL-reconstruction. Also, no evidence of a significant bracing effect could be demonstrated in the experimental in vivo or in vitro studies, except a limited stabilizing function for lower shear stress below the physiological loads. Consequently, the systematic use of braces in the rehabilitation after ACL reconstruction cannot be recommended.

Effects of a participatory ergonomics team among hospital orderlies

BACKGROUND

High rates of work-related injuries are seen among health care workers involved in lifting and transferring patients. We studied the effects of a participatory worker-management ergonomics team among hospital orderlies.

METHODS

This prospective intervention trial examined work injuries and other outcomes before and after the intervention, with other hospital employees used as a concurrent control. All orderlies in a 1,200-bed urban hospital were studied using passively collected data (mean employment during study period 100-110 orderlies); 67 orderlies (preintervention) and 88 orderlies (postintervention) also completed a questionnaire. The intervention was the formation of a participatory ergonomics team with three orderlies, one supervisor, and technical advisors. This team designed and implemented changes in training and work practices.

RESULTS

The 2-year postintervention period was marked by decreased risks of work injury (RR = 0.50, 95% CI 0.35-0.72), lost time injury (RR = 0.26, 95% CI 0.14-0.48), and injury with three or more days of time loss (RR = 0.19, 95% CI 0.07-0.53). Total lost days declined from 136.2 to 23.0 annually per 100 full-time worker equivalents (FTE). Annual workers' compensation costs declined from $237/FTE to $139/FTE. The proportion of workers with musculoskeletal symptoms declined and there were statistically significant improvements in job satisfaction, perceived psychosocial stressors, and social support among the orderlies.

CONCLUSION

Substantial improvements in health and safety were seen following implementation of a participatory ergonomics program.

Snow skiing

There are many inherent difficulties in the collection of epidemiologic ski data, but important trends have been identified. Further investigation into controllable risk factors is currently in progress in an attempt to reduce injury incidence, along with prophylactic strength training and conditioning programs. A comprehensive ski-specific training program entailing training of the energy systems, isolated and kinetic chain strength training, skill-specific training, and psychological training is essential to ensure the optimal performance and safety of the skier. Rehabilitation issues also can be addressed in the context of the above elements.

Survey of injuries and protective gear worn by in-line skaters in public parks

In-line skating, also known as rollerblading, has become popular as a recreational activity as well as a mode of transportation. Increased participation has been accompanied with a marked rise in major and minor injuries. The objective of this study was to survey active in-line skaters and to describe their demographic features, formal training, protective gear used, and a history of incurred injuries. A questionnaire was distributed to randomly selected in-line skaters in a large public park in New York City. Of the 223 skaters who responded, 128 were male and 95 were female. Ages ranged from 12 to 64 (mean, 29) yr. Some kind of injury was reported by 87 (39%) of the participants. The majority of those injuries occurred when the skaters were beginners (46). Skin abrasions and musculoligamentous injuries were the most common. Only 15 (17.2%) sought medical treatment, and of these, 5 were treated for fractures: 3 at the wrist and 1 each at the ankle and knee. The knee was the most commonly injured part of the body (24.7%), followed by the elbow and wrist. Approximately 5% of all injuries involved the head. Many skaters did not wear helmets or knee pads, even though they owned this equipment. There was a strong preference for wearing wrist pads, either alone or with other protective gear. This suggests that skaters have learned that the wrist is particularly vulnerable to serious injury and should be protected.

Analysis of acute mechanical insult in an animal model of post-traumatic osteoarthrosis

Chronic degeneration of articular cartilage and bone in a rabbit model of post-traumatic osteoarthrosis has been hypothesized to occur due to acute stresses that exceed a threshold for injury. In this study, we impacted the rabbit patellofemoral joint at low and high intensities. High-intensity impacts produced degenerative changes in the joint, such as softening of retropatellar cartilage, as measured by indentation, an increase in histopathology of the cartilage, and an increase in thickness of subchondral bone underlying the cartilage. Low-intensity impacts did not cause these progressive changes. These data suggest that low-intensity impacts produced acute tissue stresses below the injury threshold, while high-intensity impacts produced stresses that exceeded the threshold for disease pathogenesis. This study begins to identify "safe" and "unsafe" ranges of acute tissue stress, using the rabbit patella, which may have future utility in the design of injury prevention devices for the human.

Reduction of injuries in downhill skiing by use of an instructional ski-video: a prospective randomised intervention study

Despite various attempts at prevention, injury in downhill skiing continues to be a worrisome recreational problem. The purpose of this study was to test the effect of an instructional ski video on the behaviour and injuries of 763 downhill skiers. They were enrolled in two study groups, based on whether or not an instructional video had been shown in their bus on the way to a skiing resort. The video focussed on information regarding how to get started in downhill skiing and injury prevention. The outcome parameters, behaviour (binding test and adjustment), injury risk, type and consequence, were registered on the return trip 8 days later by a questionnaire. In the intervention group all outcome parameters changed significantly. The binding test was performed by 86% in the intervention group and by only 59% in the control group (P < 0.05). Adjustment of the bindings was done by 22% in the intervention group vs 14% in the control group. Regarding injury risk, 205 injuries were seen in 158 persons (20.7%) which is 26 injured skiers per 1000 skier-days and 33.6 injuries per 1000 skier-days. In the intervention group 16% of all skiers were injured vs 23% in the control group, yielding a reduction in injury risk of 30% (P < 0.05). Injuries caused by falls were seen in 12.6% in the intervention group vs 16.2% in the control group (P < 0.05). Injuries caused by collision were seen in 6% of the intervention group vs 12% in the control group (P < 0.05). The overall mean injury risk was 16 injuries per 1000 falls. Knee injuries made up 32.6% of the total. For inexperienced skiers the knee injury risk was significantly lower if the bindings had been tested (P < 0.05). Therefore, an instructional ski video can change the behaviour of downhill skiers and reduce the injury risk and consequences significantly.