Greater Risk Of Anterior Cruciate Ligament Injury Research Articles

Research Dominance Definitions May Not Identify Higher Risk Limb for Anterior Cruciate Ligament Injury in NCAA D3 Student-Athletes.

Background/PurposeRecent work has identified non-significant correlations of established limb dominance to the lower extremity (LE) at greater risk for Anterior Cruciate Ligament (ACL) injury in an active, non-athletic sample. The most common LE dominance definition is preferred leg to kick a ball. Athletes develop a unilaterality pattern different from their active, non-athlete peers. Therefore, the purpose of this study was to explore the correlation between the LE used to kick a ball with and the limb identified at greater risk of ACL injury in National Collegiate Athletic Association (NCAA) Division III athletes.DesignAn Observational Descriptive study designMethodsForty-six student-athletes that were active on their NCAA Division III football, field hockey, volleyball, and soccer team rosters were recruited. Upon completing consent, participants performed two tasks (kicking a ball; unilateral land) in a counterbalanced order. Data were entered into and analyzed with a commercial statistical software package where a phi coefficient and Chi-squared analysis were performed.ResultsOf the 46 student athletes who participated (Female=32, Male=14, 19.48±1.26years, 171.75±10.47cm, 77.26±18.74kg), 25 participants kicked and landed with the same limb. Twenty participants chose kicking and landing with different limbs. The Phi Coefficient (Φ= 0.001; P= 0.97) indicated little to no relationship between the LE a participant kicked and landed with. Likewise, the Chi-square statistic revealed no statistical differences between observed and expected frequencies (χ2= 0.001; p= 0.97).Discussion/ConclusionNCAA Division III athletes display a statistical absence of preferred limb predictability utilizing the most common dominance definition (kicking a ball) as it relates to identifying LE at risk of ACL injury. The results suggest that the prevalent LE dominance definition is problematic when exploring ACL injury risk in this population.

Effects of foot progression angle on knee mechanics during an anticipated cutting task: A statistical parametric mapping approach

Cutting is considered a “high-risk” movement for anterior cruciate ligament (ACL) injuries. It has been established that sex differences exist during cutting, placing females at greater ACL injury risk. Foot progression angle (FPA) during landing has been shown to influence lower extremity mechanics, yet little is known how FPA influences mechanics during cutting. The purpose of this study was to compare two FPA conditions during cutting between males and females. Twenty-four males and females were tested using two FPA conditions: toe-in 15° (TI15) and toe-out 15° (TO15). Right knee joint kinematic and kinetic variables were measured using a motion capture system and force plate. Five successful trials were collected and compared between FPA conditions. One-dimensional statistical parametric mapping was used to assess changes in knee mechanics between males and females over the entire stance phase. The only sex × FPA effect found was knee flexion angle. Females cutting at TI15 had decreased knee flexion angle compared TO15 (p = 0.019). Significant sex main effects included knee abduction and rotation angles, and knee flexion and rotation moments. Significant FPA main effects included knee flexion, abduction and rotation angles. The results show cutting with a toe-in FPA of 15° is enough to induce changes in knee abduction angle while cutting with 15° toe-out FPA influenced knee flexion and rotation angles. These data suggest that different cutting FPAs may be influential on known ACL injury risk variables. However, more research is warranted on cutting FPA before FPA is targeted as part of ACL injury prevention protocols.

Immediate Effect of Anterior Cruciate Ligament Protective Knee Taping on Knee Landing Mechanics and Muscle Activations during Side Hops.

Athletic taping is widely used in sports to prevent injury. However, the effect of anterior cruciate ligament (ACL) protective taping on neuromuscular control during dynamic tasks remains unclear. Therefore, this study aimed to investigate the immediate effect of ACL protective taping on landing mechanics and muscle activations during side hops in healthy individuals. Fifteen healthy individuals (11 males and 4 females; age, 23.1 ± 1.4 years; height, 175.1 ± 10.4 cm; weight, 66.3 ± 11.2 kg) volunteered to participate in this study. Landing mechanics and muscle activations were measured while each participant performed single-leg hops side-to-side for ten repetitions with and without taping. An optical motion capture system and two force plates were used to collect the kinematic and kinetic data during the side hops. Surface electromyogram recordings were performed using a wireless electromyography system. Paired t-tests were performed to determine the differences in landing mechanics and muscle activations between the two conditions (taping and non-taping). The level of significance was set at p < 0.05. Compared with the non-taping condition, participants landed with a smaller knee abduction angle, greater knee external rotation angle, and smaller knee extensor moment in the taping condition. Given that greater knee abduction, internal rotation, and knee extension moment are associated with a greater risk of ACL injury, our findings suggest that ACL protective taping can have an immediate effect on dynamic knee stability. Clinicians should consider using ACL protective taping to facilitate the use of favorable landing mechanics for ACL injuries.

Anterior Cruciate Ligament Injury Risk in Sport: A Systematic Review and Meta-Analysis of Injury Incidence by Sex and Sport Classification.

To evaluate sex differences in incidence rates (IRs) of anterior cruciate ligament (ACL) injury by sport type (collision, contact, limited contact, and noncontact). A systematic review was performed using the electronic databases PubMed (1969-January 20, 2017) and EBSCOhost (CINAHL, SPORTDiscus; 1969-January 20, 2017) and the search terms anterior cruciate ligament AND injury AND (incidence OR prevalence OR epidemiology). Studies were included if they provided the number of ACL injuries and the number of athlete-exposures (AEs) by sex or enough information to allow the number of ACL injuries by sex to be calculated. Studies were excluded if they were analyses of previously reported data or were not written in English. Data on sport classification, number of ACL injuries by sex, person-time in AEs for each sex, year of publication, sport, sport type, and level of play were extracted for analysis. We conducted IR and IR ratio (IRR) meta-analyses, weighted for study size and calculated. Female and male athletes had similar ACL injury IRs for the following sport types: collision (2.10/10 000 versus 1.12/10 000 AEs, IRR = 1.14, P = .63), limited contact (0.71/10 000 versus 0.29/10 000 AEs, IRR = 1.21, P = .77), and noncontact (0.36/10 000 versus 0.21/10 000 AEs, IRR = 1.49, P = .22) sports. For contact sports, female athletes had a greater risk of injury than male athletes did (1.88/10 000 versus 0.87/10 000 AEs, IRR = 3.00, P < .001). Gymnastics and obstacle-course races were outliers with respect to IR, so we created a sport category of fixed-object, high-impact rotational landing (HIRL). For this sport type, female athletes had a greater risk of ACL injury than male athletes did (4.80/10 000 versus 1.75/10 000 AEs, IRR = 5.51, P < .001), and the overall IRs of ACL injury were greater than all IRs in all other sport categories. Fixed-object HIRL sports had the highest IRs of ACL injury for both sexes. Female athletes were at greater risk of ACL injury than male athletes in contact and fixed-object HIRL sports.

A Cam Shaped Femur Might Be A Risk Factor for ACL Injuries

Objectives:Bony morphologic characteristics have been demonstrated to increase the risk of anterior cruciate ligament (ACL) injury. While posterior femoral condyle condylar offset is an aspect of distal femoral bony morphology that has been reported to influence range of motion and other aspects of knee joint kinematics, it remains unclear whether this characteristic influences the risk of ACL injury. The purpose of the study was to examine the relationship between distal femoral morphology and risks of ACL injury, reconstruction failure, and contralateral ACL injury. It was hypothesized that increased posterior femoral condylar depth, quantified as the cam ratio, would correlate with increased risk of primary ACL injuries, ACL reconstruction failures, and contralateral ACL injuries.Methods:Consecutive patients undergoing evaluation for knee complaints at an academic medical center from 2012-2016 with minimum 24-month follow-up were retrospectively reviewed. Subjects were stratified into four groups: a control group consisting of patients with no ACL injuries and three groups of patients with a primary ACL injury, failed ACL reconstruction, or previous ACL injury with subsequent contralateral ACL injury. Using lateral radiographs, the ratio of posterior condylar depth over total condylar distance was defined as the cam ratio. Analysis-of-variance (ANOVA) and post-hoc testing were used to test for differences in the mean tomahawk ratio between study groups (p<0.05). Receiver Operating Characteristic (ROC) analysis was performed to determine the optimal cam ratio cut-off for detecting increased risk for ACL injury.Results:One hundred and seventy-five patients met inclusion criteria. The mean cam ratios in the control, primary ACL injury, failed ACL reconstruction, and contralateral ACL injury groups were 61.1% (± 2.1), 64.2% (± 3.8), 64.4% (± 3.6), and 66.9% (± 4.0), respectively. Patients with a primary ACL injury, failed ACL reconstruction, or contralateral ACL injury had a significantly higher cam ratio compared to the control group (p<0.008). ROC analysis demonstrated a cam ratio of 63% or greater to be associated with an increased risk for ACL injury with a sensitivity of83% and a specificity of 71%.Conclusion:The data from this study show that an increased posterior femoral condylar depth, or cam ratio, might be associated with increased risk of ACL injury, including primary ACL injury, failed ACL reconstruction, and contralateral ACL injury. The data from this study may help clinicians identify patients at greater risk of ACL injury and re-injury. Future prospective studies will be helpful in investigating the mechanism by which an increased cam ratio increases ACL injury risk and potential strategies to mitigate the increased risk posed by this bony characteristic.

Peak Lower Extremity Landing Kinematics in Dancers and Nondancers.

Anterior cruciate ligament (ACL) injuries often occur during jump landings and can have detrimental short-term and long-term functional effects on quality of life. Despite frequently performing jump landings, dancers have lower incidence rates of ACL injury than other jump-landing athletes. Planned versus unplanned activities and footwear may explain differing ACL-injury rates among dancers and nondancers. Still, few researchers have compared landing biomechanics between dancers and nondancers. To compare the landing biomechanics of dancers and nondancers during single-legged (SL) drop-vertical jumps. Cross-sectional study. Laboratory. A total of 39 healthy participants, 12 female dancers (age = 20.9 ± 1.8 years, height = 166.4 ± 6.7 cm, mass = 63.2 ± 16.4 kg), 14 female nondancers (age = 20.2 ± 0.9 years, height = 168.9 ± 5.0 cm, mass = 61.6 ± 7.7 kg), and 13 male nondancers (age = 22.2 ± 2.7 years, height = 180.6 ± 9.7 cm, mass = 80.8 ± 13.2 kg). Participants performed SL-drop-vertical jumps from a 30-cm-high box in a randomized order in 2 activity (planned, unplanned) and 2 footwear (shod, barefoot) conditions while a 3-dimensional system recorded landing biomechanics. Overall peak sagittal-plane and frontal-plane ankle-, knee-, and hip-joint kinematics (joint angles) were compared across groups using separate multivariate analyses of variance followed by main-effects testing and pairwise-adjusted Bonferroni comparisons as appropriate ( P < .05). No 3-way interactions existed for sagittal-plane or frontal-plane ankle (Wilks λ = 0.85, P = .11 and Wilks λ = 0.96, P = .55, respectively), knee (Wilks λ = 1.00, P = .93 and Wilks λ = 0.94, P = .36, respectively), or hip (Wilks λ = 0.99, P = .88 and Wilks λ = 0.97, P = .62, respectively) kinematics. We observed no group × footwear interactions for sagittal-plane or frontal-plane ankle (Wilks λ = 0.94, P = .43 and Wilks λ = 0.96, P = .55, respectively), knee (Wilks λ = 0.97, P = .60 and Wilks λ = 0.97, P = .66, respectively), or hip (Wilks λ = 0.99, P = .91 and Wilks λ = 1.00, P = .93, respectively) kinematics, and no group × activity interactions were noted for ankle frontal-plane (Wilks λ = 0.92, P = .29) and sagittal- and frontal-plane knee (Wilks λ = 0.99, P = .81 and Wilks λ = 0.98, P = .77, respectively) and hip (Wilks λ = 0.88, P = .13 and Wilks λ = 0.85, P = .08, respectively) kinematics. A group × activity interaction (Wilks λ = 0.76, P = .02) was present for ankle sagittal-plane kinematics. Main-effects testing revealed different ankle frontal-plane angles across groups ( F2,28 = 3.78, P = .04), with male nondancers having greater ankle inversion than female nondancers ( P = .05). Irrespective of activity type or footwear, female nondancers landed with similar hip and knee kinematics but greater peak ankle eversion and less peak ankle dorsiflexion (ie, positions associated with greater ACL injury risk). Ankle kinematics may differ between groups due to different landing strategies and training used by dancers. Dancers' training should be examined to determine if it results in a reduced occurrence of biomechanics related to ACL injury during SL landing.

The effects of a 90-minute simulated soccer match-play on knee and hip kinematics

Knee and hip extension are two proposed mechanisms of non-traumatic anterior cruciate ligament (ACL) injury. This study aimed to investigate the changes of the hip extension angles following exertion induced by an overground simulated soccer match-play. Fifteen male recreational players consented to this study and were required to complete a 90 minutes of simulated soccer match-play. Knee and hip angles were measured at initial contact during 45° anticipated side-cutting tasks performed prior to the simulation (time 0 min), at the end of the first half (time 45 min) prior to the second half (time 60 min) and at the end of the soccer match simulation (time 105 min). A two (group: dominant, nondominant) × four (time: 0 min, 45 min, 60 min and 105 min) mixed between- and within- subjects ANOVA was utilized. Results revealed that both knee and hip extension angles were significantly altered over time (knee: F3,102 = 4.464, p = 0.005, η2 = 0.116; hip: F3,102 = 9.998, p = 0.000, η2 = 0.227), however no significant differences were observed between dominant and nondominant sides (knee: F1,34 = 0.026, p = 0.872, η2 = 0.001; hip: F1,34 = 0.225, p = 0.638, η2 = 0.007). Pairwise comparisons indicated that the knee and hip is more during the second half of the simulation (time 60 min and time 105 min), compared to pre-exertion (time 0 min) (p &lt; 0.05). The more erect knee and hip landing postures observed suggested a greater risk of ACL injury during the latter stage of each halves of match-play, supporting epidemiological observations. Further interrogations of the kinematic differences in the knees and hips across limb dominance are warranted for a more comprehensive understanding of the changes in a multiplanar perspective following soccer specific fatigue development.

Divided attention during cutting influences lower extremity mechanics in female athletes

Anterior cruciate ligament (ACL) injuries in basketball appear to be more common when players are in possession of the ball. The greater risk of ACL injury when in possession of the ball may result from the athlete’s inability to fully attend to their movement. However, it is also possible that having to carry/manipulate the ball restricts the athlete’s ability to utilise their upper extremities for stability during a manoeuvre. The purpose of this study was to explore how possession of a basketball and divided attention influence lower extremity mechanics during cutting and landing. Twenty uninjured females with basketball experience performed a baseline lateral cutting task, as well as lateral cuts while carrying a basketball, with and without a subsequent chest pass. Requiring participants to carry the basketball in isolation (i.e., without the additional pass) had minimal influence on lower extremity mechanics compared to baseline. However, participants demonstrated less knee flexion (40.9° vs. 47.3°) and greater knee abduction (12.2° vs. 10.1°) for trials that included the additional pass (divided attention condition) compared to trials conducted while carrying the basketball in isolation. Athletes may be at greater risk for ACL injury when they are unable to solely attend to their movement.

Associations between player age and club soccer coaches’ perceptions of injury risk and lower extremity injury prevention program use

The use of a lower extremity injury prevention program by female soccer players before the completion of puberty may mitigate movement changes that develop during puberty and contribute to post-pubescent females’ greater anterior cruciate ligament-injury risk. It is unknown whether club soccer coaches are using injury prevention programs with younger athletes and if player age is associated with soccer coaches’ knowledge, attitudes, and behaviors surrounding injury prevention programs. Fifty-four coaches of female soccer teams from Oregon and Washington states (USA) completed a web-based survey. Associations between team age (U9–U14 teams = 57 and U15–U19 teams = 19 teams) and coaches’ (a) attitudes and perceptions; and (b) injury prevention program awareness, adoption, and implementation fidelity were assessed. Coaches of U15–U19 teams perceived injuries to be more of a problem and soccer to present a high risk of injury. Coaches of older teams more strongly agreed that preventive exercises should be performed by their players during training. Injury prevention program awareness among coaches of U15–U19 and U9–U14 age groups was 79% and 60%, respectively. Injury prevention program-aware coaches of U15–U19 teams were more likely to use an injury prevention program than injury prevention program-aware coaches of U9–U14 teams (67% vs. 38%), but they were not more likely to do so with high fidelity (60% vs. 54%). Team age is associated with coaches’ short-term perceptions of injury risk, but not perceptions about the long-term ramifications of injury. Educating coaches about the potential benefits of injury prevention programs for mitigating injury-related maturational changes and the long-term ramifications of lower extremity injuries may facilitate greater use of injury prevention programs by coaches of younger female soccer players.

Relationship of ACL Injury and Posterior Tibial Slope With Patient Age, Sex, and Race.

Background:Posterior tibial slope (PTS) has been proposed as a potential risk factor for anterior cruciate ligament (ACL) injury; however, studies that have examined this relationship have provided inconclusive and sometimes contradictory results. Further characterization of this relationship may enable the medical community to identify individuals at greater risk for ACL injury and possibly characterize an anatomic target during surgical reconstruction.Purpose:The primary goal was to investigate the relationship between PTS and ACL injury. The secondary goal was to determine whether there are any patient factors, such as age, race, or sex, that correlate with ACL injury and PTS.Study Design:Cross-sectional study; Level of evidence, 3.Methods:Medical records of 221 patients who underwent magnetic resonance imaging (MRI) of the knee between January 2003 and December 2009 were reviewed. Patients were separated into 2 groups: a study group of those subjects who had undergone surgery for ACL injury (n = 107) and a control group of patients diagnosed with patellofemoral syndrome (n = 114). Demographic data were collected, and MRI images from both groups were analyzed using imaging software to obtain medial and lateral tibial slope measurements. Data were then analyzed using analysis of variance (ANOVA) comparison and a multivariable regression model to determine which, if any, patient factors were related to probability of having an ACL injury.Results:ANOVA comparison demonstrated that the study group had significantly greater values for lateral PTS (6° ± 4°; P < .001) and medial PTS (7° ± 4°; P = .002) compared with controls (5° ± 3° and 5° ± 4°, respectively). After stepwise elimination of nonsignificant variables, the final multivariable logistic regression model determined that age (odds ratio [OR], 0.94; P < .001) and lateral PTS (OR, 1.12; P = .002) had statistically significant relationships with ACL injury. Medial PTS, race, and sex were not demonstrated to be significant predictors of ACL injury in this final model.Conclusion:This study demonstrates a relationship between increased lateral PTS and ACL injury, which corroborates the findings of previously published studies. The findings presented in this article may help identify patients who are at greater risk of ACL injury and could potentially benefit from treatments aimed at modification of PTS.

Male-Female Differences in Knee Laxity and Stiffness

Background: It has been reported that over 70% of anterior cruciate ligament (ACL) injuries occur in noncontact situations and that females are at 2 to 8 times greater risk of ACL injury than males. Increased joint laxity and reduced knee stiffness in female knees have been suggested as possible explanations for the higher ACL injury rates in females. Hypothesis: Compared with male knees, female knees will demonstrate increased laxity and reduced stiffness along the anterior-posterior (AP), internal-external (IE), and varus-valgus (VV) directions. Study Design: Controlled laboratory study. Methods: Forty-seven fresh-frozen human cadaveric knees were tested (22 male and 25 female) by use of a robotic system. Mean ages were 34.6 years (range, 19-45 years) for males and 28.4 years (range, 16-42 years) for females. Joint laxity and stiffness were measured from force-vs-displacement or torque-vs-rotation curves recorded for 3 modes of testing: ±134 N AP force, ±5 N·m IE torque, and ±10 N·m VV moment. Results: Compared with male knees, female knees had greater internal laxity from 0° to 50° flexion (P < .01; maximum difference of 8.3° at 50° of flexion) and greater valgus laxity from 0° to 50° of flexion (P < .05; maximum difference of 1.6° at 50° of flexion). However, female knees exhibited greater anterior laxity only at 50° of flexion (P < .03; difference of 1.3 mm). No significant male-female differences in anterior or posterior stiffness were found. Male knees had 42% greater internal stiffness from 0° to 30° of flexion (P < .03), 35% greater valgus stiffness at 10° of flexion (P < .03), and 19% greater varus stiffness at 50° of flexion (P < .03). Conclusion: Female knees demonstrated significantly increased laxity and reduced stiffness compared with males. This finding was not uniform but was dependent on the direction tested and the knee flexion angle. Clinical Relevance: Understanding the risk factors for noncontact ACL injury is important for injury prevention. In combination with other female-specific risk factors, increased knee laxity may be a contributing factor associated with the higher rate of female ACL injuries.

Lower extremity mechanics during landing after a volleyball block as a risk factor for anterior cruciate ligament injury

ObjectivesTo compare lower extremity mechanics and energy absorption during two types of landing after a successful or unsuccessful block in volleyball and assess the risks of anterior cruciate ligament (ACL) injury. DesignCohort study. SubjectsFourteen elite male volleyball players (aged 24.5 ± 4.6 years; height 1.94 ± 0.06 m; mass 86.6 ± 7.6 kg). InterventionsSubjects were required to land on force platforms using stick landing or step-back landing (with the right lower extremity stepping back away from the net) techniques after performing a standing block jump movement. Main Outcome MeasuresVertical ground reaction force (body weight); knee flexion (degrees); knee moments (Nm/kg); and hip, knee and ankle energy absorption (J/kg). ResultsThe right lower extremity showed a greater first peak of vertical ground reaction force, a greater valgus moment, lower energy absorption by the knee, and higher energy absorption by the hip and ankle joints during step-back landing. ConclusionsThe lower extremity may be exposed to a greater risk of ACL injury when stepping back from the net during the initial impact phase after a step-back landing.

RELATIONSHIP JUMP-LANDING TECHNIQUE AND NEUROPSYCHOLOGICAL CHARACTERISTICS, IMPLICATIONS FOR ACL INJURY PREVENTION

BackgroundNeuropsychological capabilities in athletes may be associated with a predisposition to anterior cruciate ligament (ACL) injuries.ObjectiveAssess differences between male and female athletes in jump-landing technique in relation to their neuropsychological...

Incidence of Second Anterior Cruciate Ligament (ACL) Injury 2 Years after Primary ACL Reconstruction and Return to Sport

Objectives:The incidence of second anterior cruciate ligament (ACL) injury in the first 12 months after ACL reconstruction (ACLR) and return to sport in a young, active population has been reported to be 15 times greater than a previously uninjured cohort. It is unknown if this high relative rate of injury continues beyond the first year after return to sport following ACLR. The tested hypothesis was that the incidence rate of a subsequent ACL injury in the 2 years following ACLR and return to sports would be less than the incidence rate reported within the first 12 months after return to sport, but greater than the ACL injury incidence rate in an uninjured cohort of young athletes.Methods:Seventy-eight subjects who underwent ACLR and were ready to return to a pivoting/cutting sport (RTS) and 47 controls were prospectively enrolled. Each subject was followed for injury and athletic exposure (AE) data for a 24-month period after return to sport. Twenty-three subjects after ACLR and 4 control subjects suffered an ACL injury during this time. Incidence rate ratios (IRR) were calculated to compare the rates (per 1000 athletic exposures [AEs]) of ACL injury in athletes in the ACLR group and control group. For the ACLR group, similar comparisons were conducted for side of injury by sex.Results:The overall incidence rate of a second ACL injury within 24 months after ACLR and RTS (1.39/1000 AE) was nearly 6 times greater (IRR=5.71, 95% CI: 2.0, 22.7, p=0.0003) than healthy control subjects (0.24/1,000 AE). Female ACLR athletes demonstrated 4 times greater rate of injury within 24 months of RTS (IRR=4.51; 95% CI: 1.5-18.2, p=0.0004) than female controls. Within the ACLR group, there was a trend for female subjects to be over two (RR=2.43, 95% CI: 0.8, 8.6) times more likely to suffer a contralateral injury (1.13/1000 AEs) than an ipsilateral injury (0.47/1000 AEs). Overall, 29.5% of athletes suffered a second ACL injury within 24 months of RTS with 20.5% sustaining a contralateral injury and 9.0% incurring an ipsilateral graft re-tear injury. A higher proportion of females (23.7%) suffered a contralateral injury compared to males (10.5%). Conversely, for ipsilateral injuries, the incidence proportion between females (8.5%) and males (10.5%) were found to be similar.Conclusion:These data support the hypothesis that in the 24 months following ACLR and RTS, patients are at greater risk (nearly 6 times) to suffer a subsequent ACL injury compared to young athletes without a history of ACL injury. Additionally, the contralateral limb of female patients appears to be at greatest risk. These 24 month outcome data, analyzed in conjunction with recent 12 month outcome data which noted a 15 times greater risk of ACL injury compared to healthy control subject, indicate that the greatest risk of second ACL injury after ACLR occurs during the initial 12 months after ACLR and RTS than the second year after RTS.

Why Do Girls Sustain More Anterior Cruciate Ligament Injuries Than Boys?

Sport is the leading cause of injury among adolescents and girls incur more non-contact anterior cruciate ligament (ACL) ruptures than boys, with this gender disparity in injury incidence apparent from the onset of puberty. Although the mechanisms for this gender disparity in ACL injuries are relatively unknown, hormonal, anatomical and biomechanical factors have been implicated. Puberty is associated with rapid skeletal growth and hormonal influx, both of which are thought to contribute to alterations in ACL metabolic and mechanical properties, as well as changes in lower limb strength and flexibility, ultimately influencing landing technique. Therefore, the aim of this review is to explain (i) the effects of changes in estrogen levels on the metabolic and mechanical properties of the ACL; (ii) changes in musculoskeletal structure and function that occur during puberty, including changes in knee laxity, and lower limb flexibility and strength; and (iii) how these hormonal and musculoskeletal changes impact upon the landing technique displayed by pubescent girls. Despite evidence confirming estrogen receptors on the ACL, there are still conflicting results as to how estrogen affects the mechanical properties of the ACL, particularly during puberty. However, during this time of rapid growth and hormonal influx, unlike their male counterparts, girls do not display an accelerated muscle strength spurt and the development of their hamstring muscle strength appears to lag behind that of their quadriceps. Throughout puberty, girls also display an increase in knee valgus when landing, which is not evident in boys. Therefore, it is plausible that this lack of a defined strength spurt, particularly of the hamstring muscles, combined with the hormonal effects of estrogen in girls, may contribute to a more ‘risky’ lower limb alignment during landing, in turn, contributing to a greater risk of ACL injury. There is, however, a paucity of longitudinal studies specifically examining the lower limb musculoskeletal structural and functional changes experienced by girls throughout puberty, as well as how these changes are related to estrogen fluctuations characteristic of puberty and their effects on landing biomechanics. Therefore, further research is recommended to provide greater insight as to why pubescent girls are at an increased risk of non-contact ACL injuries during sport compared with boys. Such information will allow the development of evidence-based training programmes aimed at teaching girls to land more safely and with greater control of their lower limbs in an attempt to reduce the incidence of ACL ruptures during puberty.

Collagen Gene Variants Previously Associated With Anterior Cruciate Ligament Injury Risk Are Also Associated With Joint Laxity

Background:Genetic association studies demonstrate a relationship between several collagen gene variants and anterior cruciate ligament (ACL) injury, yet the mechanism of these relationships is still unclear. Joint laxity is a heritable trait; increased magnitudes of anterior knee laxity (AKL), genu recurvatum (GR), and general joint laxity (GJL) have been consistently associated with a greater risk of ACL injury. Joint laxity may constitute an important intermediate phenotype for the genetic association with ACL injury that can be measured clinically.Hypothesis:To determine if genetic variants within the COL1A1, COL5A1, and COL12A1 genes, previously associated with ACL injury, were also associated with greater magnitudes of AKL, GR, and GJL.Study Design:Descriptive laboratory study.Methods:Blood samples and measures of AKL, GR, and GJL were obtained from 124 (50 male, 74 female) healthy, recreationally active subjects. Genomic DNA was extracted from the blood samples and genotyped for single-nucleotide polymorphisms previously examined relative to ACL injury. Univariate analyses of variance compared the magnitude of each laxity variable across the 3 genotypes for each single-nucleotide polymorphism in both sex-combined and sex-specific models.Results:Specific genotypes were associated with greater GR in all subjects. Some genotypes were associated with greater magnitudes of GR, AKL, and GJL in females only.Conclusions:Gene variants previously associated with ACL injury risk were in large part also associated with joint laxity. Sex-specific genetic associations with joint laxity were consistent with those previously reported for ACL injury.Clinical Relevance:These data provide insight into potential pathways through which genotypic variants in collagen genes have the potential to alter ligament structure and behavior and, thus, ACL injury risk.

Tuck Jump Assessment for Reducing Anterior Cruciate Ligament Injury Risk

FEMALE ATHLETES demonstrate a 4 to 6 times higher incidence of non-contact anterior cruciate ligament (ACL) injury than male athletes participating in the same landing and pivoting sports.1-3 This greater risk of ACL injury, coupled with a dramatic increase in participation (doubling each decade), has led to a significant rise in the number of ACL injuries in female athletes. This gender disparity in non-contact ACL injury risk, combined with evidence that the primary cause may be neuromuscular in nature, have lead to the development of neuromuscular interventions designed to prevent injury.4-9 Initial interventions aimed at reducing the incidence of ACL injuries in female athletes were developed based on empirical evidence from coaching and training female athletes and from performance enhancement research.4,10 More current techniques, developed from identified injury mechanism (dynamic knee valgus11) and objective analysis of training methods,12-19 may further reduce traumatic ACL injuries in female athletes.5-7 The programs that have demonstrated ACL injury reduction are comprehensive, and include multiple training components that may induce the neuromuscular changes. The purpose of this report is to discuss the current evidence related to modifiable ACL injury mechanisms during landing and to present a novel “clinician-friendly” assessment and training technique that can be used to identify these mechanisms in high-risk female athletes. Key Points Use of the tuck jump assessment to identify neuromuscular imbalances may provide direction for targeted treatment for those at high risk for ACL injury. Improvement in neuromuscular techniques may be assessed and continually monitored with repeated measurement using the tuck jump assessment. Multiple factors may underlie the differences in ACL injury risk in male and females, neuromuscular control may be the most important and modifiable factor that can be addressed with plyometric training.

Gender differences in passive knee biomechanical properties in tibial rotation

The anterior cruciate ligament (ACL) is the most commonly injured knee ligament with the highest incidence of injury in female athletes who participate in pivoting sports. Noncontact ACL injuries commonly occur with both internal and external tibial rotation. ACL impingement against the lateral wall of the intercondylar notch during tibial external rotation and abduction has been proposed as an injury mechanism, but few studies have evaluated in vivo gender-specific differences in laxity and stiffness in external and internal tibial rotations. The purpose of this study was to evaluate these differences. The knees of 10 male and 10 female healthy subjects were rotated between internal and external tibial rotation with the knee at 60 degrees of flexion. Joint laxity, stiffness, and energy loss were compared between male and female subjects. Women had higher laxity (p = 0.01), lower stiffness (p = 0.038), and higher energy loss (p = 0.008) in external tibial rotation than did men. The results suggest that women may be at greater risk of ACL injury resulting from impingement against the lateral wall of the intercondylar notch, which has been shown to be associated with external tibial rotation and abduction.

The influence of gender-specific loading patterns of the stop-jump task on anterior cruciate ligament strain

Studies have shown that women are at higher risk of sustaining noncontact anterior cruciate ligament (ACL) injuries in specific sports. Recent gait studies of athletic tasks have documented that gender differences in knee movement, muscle activation, and external loading patterns exist. The objective of this study was to determine in a knee cadaver model if application of female-specific loading and movement patterns characterised in vivo for a stop-jump task cause higher ACL strains than male patterns. Gender-specific loading patterns of the landing phase of the vertical stop-jump task were applied to seven cadaver knees using published kinetic/kinematic results for recreational athletes. Loads applied consecutively included: tibial compression, quadriceps, hamstrings, external posterior tibial shear, and tibial torque. Knee flexion was fixed based on the kinematic data. Strain of the ACL was monitored by means of a differential variable reluctance transducer installed on the anterior-medial bundle of the ACL. The ACL strain was significantly increased (P<0.05) for the female loading pattern relative to the male loading pattern after the posterior tibial shear force was applied, and showed a similar trend (P=0.1) to be increased after the final tibial torque was applied. This study suggests that female motor control strategies used during the stop-jump task may place higher strains on the ACL than male strategies, thus putting females at greater risk of ACL injury. We believe these results suggest the potential effectiveness of using training programs to modify motor control strategies and thus modify the risk of injury.

Neuromuscular Training to Prevent Anterior Cruciate Ligament Injury in the Female Athlete

Despite the identification of effective anterior cruciate ligament (ACL) injury prevention exercise programs,female athletes remain at a 4- to 6-fold greater risk of ACL injury compared to male athletes. One possible explanation for the lack of improvement in ACL injury risk in female athletes is an inadequate dissemination of information regarding effective intervention strategies. This article presents gender differences in neuromuscular control that may place the female athlete at increased risk for ACL injury and information on the design and implementation of a neuromuscular training program to reduce the risk of ACL injury in female athletes