Prevention of non-contact anterior cruciate ligament injuries in soccer players. Part 2: A review of prevention programs aimed to modify risk factors and to reduce injury rates

Soccer is the most commonly played sport in the world, with an estimated 265 million active soccer players participating in the game as on 2006. Inherent to this sport is the higher risk of injury to the anterior cruciate ligament (ACL) relative to other sports. ACL injury causes a significant loss of time from competition in soccer, which has served as the strong impetus to conduct research that focuses to determine the risk factors for injury, and more importantly, to identify and teach techniques to reduce this injury in the sport. This research emphasis has afforded a rapid influx of literature aimed to report the effects of neuromuscular training on the risk factors and the incidence of non-contact ACL injury in high-risk soccer populations. The purpose of the current review is to sequence the most recent literature relating the effects of prevention programs that were developed to alter risk factors associated with non-contact ACL injuries and to reduce the rate of non-contact ACL injuries in soccer players. To date there is no standardized intervention program established for soccer to prevent non-contact ACL injuries. Multi-component programs show better results than single-component preventive programs to reduce the risk and incidence of non-contact ACL injuries in soccer players. Lower extremity plyometrics, dynamic balance and strength, stretching, body awareness and decision-making, and targeted core and trunk control appear to be successful training components to reduce non-contact ACL injury risk factors (decrease landing forces, decrease varus/valgus moments, and increase effective muscle activation) and prevent non-contact ACL injuries in soccer players, especially in female athletes. Pre-season injury prevention combined with an in-season maintenance program may be advocated to prevent injury. Compliance may in fact be the limiting factor to the overall success of ACL injury interventions targeted to soccer players regardless of gender. Thus, interventional research must also consider techniques to improve compliance especially at the elite levels which will likely influence trickle down effects to sub-elite levels. Future research is also needed for male soccer athletes to help determine the most effective intervention to reduce the non-contact ACL injury risk factors and to prevent non-contact ACL injuries.     

Mechanisms of non-contact ACL injuries

In soccer one of the most common knee injuries is the anterior cruciate ligament (ACL) tear, which usually occurs through non-contact mechanisms. Female soccer players are at higher risk of sustaining non-contact ACL injuries than male soccer players. A good understanding of ACL loading mechanisms is the basis for a good understanding of the mechanisms of non-contact ACL injuries, which in turn is essential for identifying risk factors and developing prevention strategies. Current literature demonstrates that sagittal plane biomechanical factors, such as small knee flexion angle, great posterior ground reaction force and great quadriceps muscle force, are the major ACL loading mechanisms. A great posterior ground reaction force may be associated with a great quadriceps muscle force, which would cause great anterior draw force at the knee. A small knee flexion is associated with a large patella tendon-tibia shaft angle and ACL elevation angle, which would result in great ACL loading. Current literature also demonstrates that the ACL is not the major structure of bearing knee valgus-varus moment and internal-external rotation loadings. Knee valgus-varus moment and internal-external rotation moment alone are not likely to result in isolated ACL injuries without injuring other knee structures.     

Lower extremity kinematics and kinetics of Division III collegiate baseball and softball players while performing a modified pro-agility task

AIM: Females experience at least twice as many non-contact anterior cruciate ligament (ACL) injuries as males. The aim of this study was to investigate if males and females exhibited different characteristics while performing a modified pro-agility test. METHODS: Collegiate Division III male baseball (n=14) and female softball (n=13) players performed 4 trials of a modified pro-agility task, which consisted of running toward a force platform target for 5 steps, planting their right foot, and propelling themselves off of the target with their left foot. Kinematic and kinetic parameters were compared using a multivariate analysis of variance between gender with the level of significance set at P<0.05. RESULTS: Males and females exhibited similar knee valgus angles. Females had a greater maximum knee extension angle (10.14 degrees vs 17.43 degrees ), and greater knee range of motion (46.12 degrees vs 40.12 degrees ). Both groups reached maximum knee flexion at 52% of stance. Females had significantly more maximum hip flexion than males (28.86 degrees vs 22.75 degrees ). Females had significantly smaller minimum internal knee varus moments than their male counterparts (1.12 Nm/kg vs 1.55 Nm/kg). Vertical ground reaction forces as a percentage of bodyweight, and stance time, were not statistically different. The female group displayed an external knee rotation angle (2.49 degrees ) during the beginning of their stance, which was significantly different than the internal rotation angle (4.11 degrees ) in the male group. Early in stance knee rotation angle was highly correlated with the lack of internal knee varus moment (males R(2)=0.75, females R(2)=0.88). CONCLUSION: Females displayed knee moments and kinematics that may place them at greater risk for ACL injury during a stop-cut task. Females should be coached to perform stop cuts with more knee flexion and a more neutral knee rotation angle upon foot contact in an effort to reduce moments that may place the ACL at risk.     

The influence of in-season injury prevention training on lower-extremity kinematics during landing in female soccer players.

OBJECTIVE: To examine the influence of in-season injury prevention training on hip and knee kinematics during a landing task. DESIGN: Longitudinal pre-post intervention study. SETTING: Testing sessions were conducted in a biomechanics research laboratory. PARTICIPANTS: Eighteen female soccer players between the ages of 14 and 17 participated in this study. All subjects were healthy with no current complaints of lower extremity injury. INTERVENTIONS: Testing sessions were conducted prior to and following a season of soccer practice combined with injury prevention training. MAIN OUTCOME MEASUREMENTS: During each testing session three-dimensional kinematics were collected while each subject performed a drop landing task. Peak hip and knee joint angles were measured during the early deceleration phase of landing and compared between pre- and post-training using paired t-tests. RESULTS: Following a season of soccer practice combined with injury prevention training, females demonstrated significantly less hip internal rotation (7.1 degrees vs. 1.9 degrees; P = 0.01) and significantly greater hip abduction (-4.9 degrees vs. -7.7 degrees; P = 0.02). No differences in knee valgus or knee flexion angles were found post-season. CONCLUSIONS: Female soccer players exhibited significant changes in hip kinematics during a landing task following in-season injury prevention training. Our results support the premise that a season of soccer practice combined with injury prevention training is effective in altering lower extremity motions that may play a role in predisposing females to ACL injury.     

Effect of gender and defensive opponent on the biomechanics of sidestep cutting

PURPOSE: Anterior cruciate ligament (ACL) injuries often occur in women during cutting maneuvers to evade a defensive player. Gender differences in knee kinematics have been observed, but it is not known to what extent these are linked to abnormal neuromuscular control elsewhere in the kinetic chain. Responses to defense players, which may be gender-dependent, have not been included in previous studies. This study determined the effects of gender and defense player on entire lower extremity biomechanics during sidestepping. METHODS: Eight male and eight female subjects performed sidestep cuts with and without a static defensive opponent while 3D motion and ground reaction force data were recorded. Peak values of eight selected motion and force variables were, as well as their between-trial variabilities, submitted to a two-way (defense x gender) ANOVA. A Bonferroni-corrected alpha level of 0.003 denoted statistical significance. RESULTS: Females had less hip and knee flexion, hip and knee internal rotation, and hip abduction. Females had higher knee valgus and foot pronation angles, and increased variability in knee valgus and internal rotation. Increased medial ground reaction forces and flexion and abduction in the hip and knee occurred with the defensive player for both genders. CONCLUSIONS: A simulated defense player causes increased lower limb movements and forces, and should be a useful addition to laboratory protocols for sidestepping. Gender differences in the joint kinematics suggest that increased knee valgus may contribute to ACL injury risk in women, and that the hip and ankle may play an important role in controlling knee valgus during sidestepping. Consideration of the entire lower extremity contributes to an understanding of injury mechanisms and may lead to better training programs for injury prevention.     

Altered hip control during a standing knee-lift test is associated with increased risk of knee injuries

A few prospective studies have investigated hip and pelvic control as a risk factor for lower extremity (LE) injuries. The purpose of this study was to investigate whether deficits in hip and lumbopelvic control during standing knee-lift test are associated with increased risk of acute knee and LE injuries in youth team sports. At baseline, 258 basketball and floorball players (aged 12-21 years) participated in a standing knee-lift test using 3-dimensional motion analysis. Two trials per leg were recorded from each participant. Peak sagittal plane pelvic tilt and frontal plane pelvic drop/hike were measured. Both continuous and categorical variables were analyzed. New non-contact LE injuries, and match and training exposure, were recorded for 12 months. Seventy acute LE injuries were registered. Of these, 17 were knee injuries (eight ACL ruptures) and 35 ankle injuries. Risk factor analyses showed that increased contralateral pelvic hike was significantly associated with knee injury risk when using categorical variable (HR for high vs low group 4.07; 95% CI 1.32-12.6). Furthermore, significant association was found between high lateral pelvic hike angles and ACL injury risk in female players (HR for high vs low group 9.10; 95% CI 1.10-75.2). Poor combined sensitivity and specificity of the test was observed. In conclusion, increased contralateral pelvic hike is associated with non-contact knee injury risk among young team sport players and non-contact ACL injuries among female players. More research to determine the role of pelvic control as a risk factor for knee injuries is needed.     

Effect of gender on lower extremity kinematics during rapid direction changes: An integrated analysis of three sports movements

Anterior cruciate ligament (ACL) injury is a common sports injury, particularly in females. Gender differences in knee kinematics have been observed for specific movements, but there is limited information on how these findings relate to other joints and other movements. Here we present an integrated analysis of hip, knee and ankle kinematics across three movements linked to non-contact ACL injury. It was hypothesised that there are gender differences in lower extremity kinematics, which are consistent across sports movements. Ten female and ten male NCAA basketball players had three-dimensional hip, knee and ankle kinematics quantified during the stance phase of sidestep, sidejump and shuttle-run tasks. For each joint angle, initial value at contact, peak value and between-trial variability was obtained and submitted to a two-way mixed design ANOVA (gender and movement), with movement condition treated as a repeated measure. Females had higher peak knee valgus and lower peak hip and knee flexion, with the same gender differences also existing at the beginning of stance (p<0.05). Peak valgus measures were highly correlated between movements, but not to static valgus alignment. Kinematic differences demonstrated by females for the sports movements studied, and in particular knee valgus, may explain their increased risk of ACL injury. These differences appear to stem largely from subject-specific neuromuscular mechanisms across movements, suggesting that prevention via neuromuscular training is possible.     

Coordination and variability during anticipated and unanticipated sidestepping

BackgroundNumerous investigations have attempted to link the incidence and risk of non-contact anterior cruciate ligament injuries to specific intrinsic and extrinsic mechanisms. However, these are often measured in isolation.Research questionThis study utilizes a dynamical systems approach to investigate differences in coordination and coordination variability between segments and joints in anticipated and unanticipated sidestepping, a task linked to a high risk of non-contact anterior cruciate ligament injuries.MethodsFull body, three-dimensional kinematics and knee kinetic data were collected on 22 male collegiate soccer players during anticipated and unanticipated sidestepping tasks. A modified vector coding technique was used to quantify coordination and coordination variability of the trunk and pelvis segments and the hip and knee joints.ResultsSagittal and frontal plane trunk-pelvis coordination were more in-phase during unanticipated sidestepping. Sagittal plane hip-knee and hip (rotation)-knee (flexion/extension) coordination were more in-phase with the knee dominating the movement during unanticipated sidestepping (P < 0.05). Coordination variability was greater in unanticipated sidestepping for trunk (flexion)-pelvis (tilt), trunk (lateral flexion)-pelvis (obliquity), hip (flexion/extension)-knee (flexion/extension) and hip (rotation)-knee (flexion/extension) (P < 0.05). In unanticipated sidestepping where there is limited time to pre-plan the movement, multiple kinematic solutions and high coordinative variability is required to achieve the task.SignificanceOur results suggest that coordination becomes more in-phase and the variability of this coordination increases as a function of task complexity and reduced planning time as that which occurs in unanticipated sporting task scenarios. Consequently, injury prevention programs must incorporate perceptual components in order to optimise planning time and coordinate appropriate postural adjustments to reduce external knee joint loading and subsequent injury risk in sport.     

Prevalence of bowlegs among child and adolescent soccer players.

OBJECTIVE: Little is known about the interactions of sports-related demands and human body, in particular on musculoskeletal features, during growth. Focusing on the relationship between soccer and lower limb alignment, we examined the hypothesis that varus knee deviation is more prevalent among high-performance pediatric and adolescent soccer players. DESIGN: Cross-sectional study with focused sampling. SETTING: First league sports clubs. PARTICIPANTS: 106 male child/adolescent soccer players aged 10 to 21 years and 68 age-matched tennis players. INTERVENTIONS: All athletes completed a demographic questionnaire and underwent physical examinations, which included height, weight, generalized laxity, knee, ankle, foot and spine axis, hip range of motion, tibial torsion, Q angle, foot navicular height, and progression angle. MAIN OUTCOME MEASUREMENT: Varus/valgus axis was determined by the intercondylar intermalleolar distance while standing. Soccer and tennis players were compared on knee axis and other outcome variables by analysis of covariance, adjusting for age and by t-tests within age groups. RESULTS: A significantly higher prevalence of knee varus was found among the soccer players compared to that among the tennis players. The difference in intracondylar distance was statistically significant after the age of 13 years (P < 0.001). In addition, compared to tennis players, soccer players had higher foot arches, decreased hip external rotation and increased external tibial torsion. CONCLUSIONS: Varus knee axis deviation was more common among children and adolescent soccer players than among tennis players. The prevalence was more pronounced among players aged 13 years or older. Further research is needed to explore the rationale of this phenomenon.     

Biomechanical evaluation of the side-cutting manoeuvre associated with ACL injury in young female handball players

Purpose

The purpose of the study was to investigate the biomechanics of the knee and hip joint during handball-specific side-cutting on the dominant and non-dominant leg. Understanding the sports-specific biomechanics may improve prevention measures and post-injury treatment.

Methods

Twenty-four young female elite handball players performed 5 handball side-cutting manoeuvres on the dominant and non-dominant legs. The local maxima of the joint moments in each plane, during the initial 100 ms following foot contact, were collected.

Results

External knee moments of flexion, outward rotation and valgus—along with external hip moments of extension, abduction and internal rotation—were observed, coincidentally 30–40 ms after foot contact. No side-to-side asymmetries were found. The external moments observed support the injury mechanisms previously described in case studies of handball injuries.

Conclusion

The results underline the importance of implementing preventive exercises that increase activity of medial hamstrings, to match the external outward rotating knee moments and knee valgus moments, and increase activity of hip external rotators to match the external hip inward-rotating moment. Furthermore, the results may yield further information to the graft selection decision before ACL surgery.

Level of evidence

Diagnostic studies, Level II.     

Differences in kinematics of single leg squatting between anterior cruciate ligament-injured patients and healthy controls

Seventy to eighty percent of all anterior cruciate ligament (ACL) injuries are due to non-contact injury mechanisms. It has been reported that the majority of injuries due to single leg landing come from valgus positioning of the lower leg. Preventing valgus positioning during single leg landing is expected to help reduce the number of ACL injuries. We found that many ACL-deficient patients cannot perform stable single leg squatting. Therefore, we performed 3D motion analysis of the single-legged half squat for ACL-injured patients to evaluate its significance as a risk factor for ACL injuries. We evaluated the relative angles between the body, thigh, and lower leg using an electromagnetic device during single leg half squatting performed by 63 ACL-injured patients (32 males, 31 females) the day before ACL reconstruction and by 26 healthy control subjects with no knee problems. The uninjured leg of ACL-injured male subjects demonstrated significantly less external knee rotation than that of the dominant leg of the male control. The uninjured leg of ACL-injured female subjects demonstrated significantly more external hip rotation and knee flexion and less hip flexion than that of the dominant leg of the female control. Comparing injured and uninjured legs, the injured leg of male subjects demonstrated significantly less external knee and hip rotation, less knee flexion, and more knee varus than that of the uninjured leg of male subjects. The injured leg of female subjects demonstrated more knee varus than that of the uninjured leg of female subjects. Regarding gender differences, female subjects demonstrated significantly more external hip rotation and knee valgus than male subjects did in both the injured and uninjured legs (P < 0.05). The current kinematic study exhibited biomechanical characteristics of female ACL-injured subjects compared with that of control groups. Kinematic correction during single leg half squat would reduce ACL reinjury in female ACL-injured subjects.     

Kinematic analysis of pressing situations in female collegiate football games: New insight into anterior cruciate ligament injury causation

The most common events during which anterior cruciate ligament (ACL) injuries occur in football are pressing situations. This study aimed to describe the knee and hip joint kinematics during pressing situations in football games to identify kinematic patterns in actions with a high risk for ACL injuries. We filmed 5 female collegiate football matches and identified 66 pressing situations. Five situations with a large distance between the trunk and foot placements in the sagittal plane were analyzed using a model‐based image‐matching technique. The mean knee flexion angle at initial contact (IC) was 13° (range, 8°‐28°) and increased by 11° (95% confidence interval [CI], 3°‐14°) at 40 ms after IC. As for knee adduction and rotation angles, the knee positions were close to neutral at IC, and only minor knee angular changes occurred later in the sequences. The mean hip flexion was 25° (range, 8°‐43°) at IC and increased by 22° (95% CI, 11°‐32°) after 100 ms. The hip was also externally rotated by 7° (range, −19° to 3°) at IC, and gradually rotated internally, reaching 10° of internal rotation (range, −5° to 27°) at 100 ms after IC. This study suggests that the observed knee valgus, internal hip and knee rotation, and static hip flexion previously reported in non‐contact ACL injury events are unique to injury situations. In contrast, neither rapid knee valgus nor increased internal rotation was seen in non‐injury pressing maneuvers.     

Influence of hip restriction on noncontact ACL rerupture

Purpose

This study investigated variables associated with hip restriction (reduced range of motion) in a group of soccer players presenting with noncontact rerupture of the anterior cruciate ligament (ACL) and compared results with a group of sport-matched healthy professional athletes.

Methods

In this case series, 28 male soccer players with noncontact ACL rerupture were examined for clinical hip range of motion findings potentially associated with ACL rerupture, namely anterior knee displacement, internal–external hip rotation, and cruciate ligament insufficiency. Results were compared with data obtained from 27 healthy professional players. Patients presenting gross surgical errors (e.g. poorly positioned tunnel) or reporting major accidents affecting the lower limbs, such as leg or ankle fractures, were excluded from analysis. Internal–external rotation was measured in the supine position, with knee and hip at 90° of flexion. ACL insufficiency was assessed using the Pivot Shift test and the Lachman’s test with the aid of a Rolimeter RM^® arthrometer and confirmed by magnetic resonance imaging.

Results

The most prevalent finding was a significantly lower mean internal–external hip rotation in the rerupture group (45.0°) when compared with healthy professional soccer players (56.2°).

Conclusion

Assessing hip restriction in patients presenting noncontact ACL rerupture showed to be extremely important during ACL reconstruction planning.

Level of evidence

IV.     

Two-dimensional motion analysis of dynamic knee valgus identifies female high school athletes at risk of non-contact anterior cruciate ligament injury

Purpose

Female athletes are at greater risk of non-contact ACL injury. Three-dimensional kinematic analyses have shown that at-risk female athletes have a greater knee valgus angle during drop jumping. The purpose of this study was to evaluate the relationship between knee valgus angle and non-contact ACL injury in young female athletes using coronal-plane two-dimensional (2D) kinematic analyses of single-leg landing.

Methods

Two hundred ninety-one female high school athletes newly enrolled in basketball and handball clubs were assessed. Dynamic knee valgus was analysed during single-leg drop jumps using 2D coronal images at hallux–ground contact and at maximal knee valgus. All subjects were followed up for 3 years for ACL injury. Twenty-eight (9.6%) of 291 athletes had ACL rupture, including 27 non-contact ACL injuries. The injured group of 27 knees with non-contact ACL injury was compared with a control group of 27 randomly selected uninjured knees. The relationship between initial 2D movement analysis results and subsequent ACL injury was investigated.

Results

Dynamic knee valgus was significantly greater in the injured group compared to the control group at hallux–ground contact (2.1 ± 2.4 vs. 0.4 ± 2.2 cm, P = 0.006) and at maximal knee valgus (8.3 ± 4.3 vs. 5.1 ± 4.1 cm, P = 0.007).

Conclusion

The results of this study confirm that dynamic knee valgus is a potential risk factor for non-contact ACL injury in female high school athletes. Fully understanding the risk factors that increase dynamic knee valgus will help in designing more appropriate training and interventional strategies to prevent injuries in at-risk athletes.

Level of evidence

Prognostic studies, Level II.

     

Sex differences in proximal control of the knee joint

Following the onset of maturation, female athletes have a significantly higher risk for anterior cruciate ligament (ACL) injury compared with male athletes. While multiple sex differences in lower-extremity neuromuscular control and biomechanics have been identified as potential risk factors for ACL injury in females, the majority of these studies have focused specifically on the knee joint. However, increasing evidence in the literature indicates that lumbo-pelvic (core) control may have a large effect on knee-joint control and injury risk. This review examines the published evidence on the contributions of the trunk and hip to knee-joint control. Specifically, the sex differences in potential proximal controllers of the knee as risk factors for ACL injury are identified and discussed. Sex differences in trunk and hip biomechanics have been identified in all planes of motion (sagittal, coronal and transverse). Essentially, female athletes show greater lateral trunk displacement, altered trunk and hip flexion angles, greater ranges of trunk motion, and increased hip adduction and internal rotation during sport manoeuvres, compared with their male counterparts. These differences may increase the risk of ACL injury among female athletes. Prevention programmes targeted towards trunk and hip neuromuscular control may decrease the risk for ACL injuries.     

The epidemiology of anterior cruciate ligament injury in football (soccer): a review of the literature from a gender-related perspective

Football (soccer), the most popular sport worldwide, is associated with a high injury risk, and the knee joint is often affected. Several studies have found female players to be more susceptible to knee injury, anterior cruciate ligament (ACL) injury in particular, compared to their male counterparts. There is, however, some controversy regarding the magnitude of this risk increase and a few studies have found no differences. The influence of age and activity type on gender-related differences in injury risk is only scarcely investigated. In this paper, the literature reporting gender-specific ACL injury risk in football is reviewed. A literature search yielded 33 relevant articles that were included for review. These show that female players have a 2–3 times higher ACL injury risk compared to their male counterparts. Females also tend to sustain their ACL injury at a younger age than males, and a limiting factor in the existing literature is that age is not adjusted for in comparisons of ACL injury risk between genders. Furthermore, the risk increase in females is primarily evident during match play, but type of exposure is also rarely adjusted for. Finally, the studies included in this review share important methodological limitations that are discussed as a starting point for future research in the field.     

Association between ankle angle at initial contact and biomechanical ACL injury risk factors in male during self-selected single-leg landing

BackgroundIncreasing the ankle plantar-flexion angle at initial contact (IC) during landing reduces the impact features associated with landing, such as the vertical ground reaction force and loading rate, potentially affecting the risk of anterior cruciate ligament (ACL) injury. However, the relationships between the ankle plantar-flexion angle at IC and the previously identified biomechanical factors related to noncontact ACL injury have not been studied.Research questionThus, the purpose of this study was to determine whether significant relationships exist between the ankle plantar-flexion angle at IC and the biomechanical factors related to noncontact ACL injury.MethodsThe peak anterior tibial shear force, peak external knee valgus moment, peak knee valgus angle, and combined peak external knee valgus plus tibial internal rotation moments were measured in 26 individuals while performing self-selected, single-leg landing. Pearson correlation analyses were performed to assess the relationships between the ankle plantar-flexion angle at IC and the biomechanical factors mentioned above.ResultsThe greater ankle plantar-flexion angle at IC was related to smaller the peak knee valgus moment (r = −0.5, p = 0.009) and the combined peak knee valgus plus internal rotation moments (r = −0.58, p = 0.001).SignificanceThese results suggest that large ankle plantar-flexion angle at IC might be associated with lesser loading of the knee frontal plane and altering the self-selective ankle angle may result in biomechanical changes associated with ACL injury risk.     

Anticipatory effects on knee joint loading during running and cutting maneuvers.

PURPOSE: To determine how unanticipated performance of cutting maneuvers in sport affects the external loads applied to the knee joint and the potential risk for ligament injury. METHODS: A 50-Hz VICON motion analysis system was used to determine the lower limb kinematics of 11 healthy male subjects during running and cutting tasks performed under preplanned (PP) and unanticipated (UN) conditions. Subjects performed the UN tasks in response to a light stimulus on a target board. A kinematic model was then used in conjunction with force place data to calculate the three-dimensional loads at the knee joint. RESULTS: External flexion/extension moments at the knee joint were similar between PP and UN conditions; however, the varus/valgus and internal/external rotation moments during the UN cutting tasks were up to twice the magnitude of the moments measured during the PP condition. CONCLUSION: Cutting maneuvers performed without adequate planning may increase the risk of noncontact knee ligament injury due to the increased external varus/valgus and internal/external rotation moments applied to the knee. These results are probably due to the small amount of time to make appropriate postural adjustments before performance of the task, such as the position of the foot on the ground relative to the body center of mass. Subsequently, training for the game situation should involve drills that familiarize players with making unanticipated changes of direction. Practice sessions should also incorporate plyometrics and should focus on better interpretation of visual cues to increase the time available to preplan a movement.     

Efficacy of ACL injury risk screening methods in identifying high‐risk landing patterns during a sport‐specific task

Screening methods sensitive to movement strategies that increase anterior cruciate ligament (ACL) loads are likely to be effective in identifying athletes at‐risk of ACL injury. Current ACL injury risk screening methods are yet to be evaluated for their ability to identify athletes' who exhibit high‐risk lower limb mechanics during sport‐specific maneuvers associated with ACL injury occurrences. The purpose of this study was to examine the efficacy of two ACL injury risk screening methods in identifying high‐risk lower limb mechanics during a sport‐specific landing task. Thirty‐two female athletes were screened using the Landing Error Scoring System (LESS) and Tuck Jump Assessment. Participants' also completed a sport‐specific landing task, during which three‐dimensional kinematic and kinetic data were collected. One‐dimensional statistical parametric mapping was used to examine the relationships between screening method scores, and the three‐dimensional hip and knee joint rotation and moment data from the sport‐specific landing. Higher LESS scores were associated with reduced knee flexion from 30 to 57 ms after initial contact (P = 0.003) during the sport‐specific landing; however, no additional relationships were found. These findings suggest the LESS and Tuck Jump Assessment may have minimal applicability in identifying athletes' who exhibit high‐risk landing postures in the sport‐specific task examined.