Relationship of the menstrual cycle phase to anterior cruciate ligament injuries in teenaged female athletes Relaxin Receptors in the Human Female Anterior Cruciate Ligament The Menstrual Cycle, Sex Hormones, and Anterior Cruciate Ligament Injury. Knee ligament behavior following a controlled loading protocol does not differ by menstrual cycle day. The Effects of Generalized Joint Laxity on Risk of Anterior Cruciate Ligament Injury in Young Female Athletes Intraarticular Injuries Associated with Anterior Cruciate Ligament Tear: Findings at Ligament Reconstruction in High School and Recreational Athletes Intercondylar notch size and anterior cruciate ligament injuries in athletes Risk Factors Associated with Noncontact Injury of the Anterior Cruciate Ligament A Randomized Controlled Trial to Prevent Noncontact Anterior Cruciate Ligament Injury in Female Collegiate Soccer Players Incidence of Subsequent Injury to Either Knee within 5 Years after Anterior Cruciate Ligament Reconstruction with Patellar Tendon Autograft Biomechanical Measures of Neuromuscular Control and Valgus Loading of the Knee Predict Anterior Cruciate Ligament Injury Risk in Female Athletes: A Prospective Study Lack of effect of a knee ligament injury prevention program on the incidence of noncontact anterior cruciate ligament injury. A prospective cohort study of anterior cruciate ligament injuries in elite Norwegian team handball. A comparison of dynamic coronal plane excursion between matched male and female athletes when performing single leg landings. Effectiveness of a Neuromuscular and Proprioceptive Training Program in Preventing Anterior Cruciate Ligament Injuries in Female Athletes The Association of the Menstrual Cycle with the Laxity of the Anterior Cruciate Ligament in Adolescent Female Athletes Gender Differences in Muscular Protection of the Knee in Torsion in Size-Matched Athletes Association between lower extremity posture at contact and peak knee valgus moment during sidestepping: implications for ACL injury. Effect of Fatigue on Knee Kinetics and Kinematics in Stop-Jump Tasks Incidence of Contralateral and Ipsilateral Anterior Cruciate Ligament (ACL) Injury After Primary ACL Reconstruction and Return to Sport Biomechanical Measures during Landing and Postural Stability Predict Second Anterior Cruciate Ligament Injury after Anterior Cruciate Ligament Reconstruction and Return to Sport Association of Noncontact Anterior Cruciate Ligament Injury With Presence and Thickness of a Bony Ridge on the Anteromedial Aspect of the Femoral Intercondylar Notch The influence of gender on knee kinematics, kinetics and muscle activation patterns during side-step cutting.
Introduction Anterior cruciate ligament ( ACL ) injuries are more common among female athletes compared to male athletes . Several studies have been reported to explain the gender difference in ACL injury rates and several risk factors underlying gender disparity are believed to exist . Hormonal effects are considered to be one of the etiological factors for female non-contact ACL injuries . The objectives of this study were to determine if ACL injuries occurred r and omly or correlated with a specific phase of the female menstrual cycle in teenaged female athletes and then to determine if pre-menstrual and menstrual dysfunctions influenced these ACL injuries . Material s and methods Eighteen of 37 consecutive female athletes , with ACL injuries , met the study criteria : teenage , with regular menstrual cycle , and non-contact injury . The menstrual history , athletic activity , and injury history were collected . Results Seventy-two percent of the subjects had premenstrual symptoms and 83 % had  menstrual symptoms . The subjective activity level at the follicular phase was significantly lowest between the phases . A significant statistical association was found between the phase of the menstrual cycle and ACL injuries ( P = 0.0002 ) . There were more injuries in the ovulatory phase than expected , and fewer injuries occurred in the other phases . Conclusion The results showed a significant increase in non-contact ACL injuries in teenage female athletes during the ovulatory phase of the menstrual cycle and the subjective activity level and the premenstrual and menstrual symptoms might not affect the likelihood of the injuries . These findings suggest that sex hormones might play a role in the incidence of female non-contact ACL injuries Background Noncontact anterior cruciate ligament injuries occur two to eight times more often in women than in men . Changes in ligament laxity and strength have been associated with female hormones such as relaxin . Hypothesis Relaxin receptors are present within the female anterior cruciate ligament . Study Design Controlled laboratory study . Methods Remnants of anterior cruciate ligament were harvested from five women and five men undergoing routine ligament reconstruction . Relaxin was biotinylated and analyzed for biologic activity with use of the mouse interpubic ligament bioassay . Immunohistochemical localization of relaxin receptors was performed with appropriate negative controls and competitive binding assays to determine receptor specificity and saturability . Results Anterior cruciate ligament sections from women but not from men showed uniform specific binding that was limited to synovial lining cells , stromal fibroblasts , and cells lining blood vessels . Specific binding was confirmed in the presence of a 2000-fold excess of human insulin , the structural homolog of relaxin , and competitive inhibition was demonstrated in the presence of a 2000-fold excess of unlabeled relaxin . Conclusions Relaxin exhibits specific saturable binding in the female anterior cruciate ligament , where specific relaxin receptors were present . Clinical Relevance The high incidence of anterior cruciate ligament rupture in female athletes may be partially explained by the effects of relaxin OBJECTIVE : To determine if anterior cruciate ligament ( ACL ) injuries in female athletes occur r and omly or correlate with a specific phase of the menstrual cycle . DESIGN AND SETTING : Female athletes who sustained ACL injuries reported the days of their menstrual cycles and provided saliva sample s for sex-hormone determination . Salivary sex-hormone profiles were assessed to confirm the self-reported menstrual histories . SUBJECTS : A total of 38 female athletes ( 20 college , 15 high school , 1 middle school , 2 recreational ) with recent ACL injuries participated in the study over a 3-year period . MEASUREMENTS : Athletes with recent ACL injuries completed a question naire defining the injury , the last menstrual cycle , prior knee injury , school , and type of birth control used ( if any ) . Each subject provided a 30-cc saliva sample within 72 hours of injury . Saliva sample s were placed into sealed containers and frozen at -20 degrees C. We obtained 13 additional control sample s from uninjured females to test the correlation between saliva and serum sex-hormone levels . Progesterone and estrogen were assayed by radioimmunoassay . Physical examination , magnetic resonance imaging , or surgery confirmed the injury in all subjects . RESULTS : The correlations between saliva and serum estrogen and progesterone were 0.73 ( alpha = .01 ) and 0.72 ( alpha = .01 ) , respectively . Ten of 27 athletes who reported their cycle day at time of injury sustained an ACL injury immediately before or 1 to 2 days after the onset of menses . We rejected the null hypothesis that such high frequency was due to r and om chance . CONCLUSIONS : A significantly greater number of ACL injuries occurred on days 1 and 2 of the menstrual cycle . Salivary sex-hormone levels correlated with the reported cycle day BACKGROUND Females experience a disproportionate number of anterior cruciate ligament injuries compared to males . Increased estradiol concentration has been suggested to alter ligament properties and strength . Determining whether the knee responds differently to an external load at various hormonal levels may be helpful in further explaining the gender disparity . METHODS  Estradiol , progesterone and testosterone  were quantified at menses , near ovulation and at the mid-luteal phase . With one knee serving as the control limb and the other as the experimental limb , displacement at 134N and stiffness between 90 and 134N were recorded with a knee ligament arthrometer on both knees before and after a loading protocol . The protocol consisted of three , 3-min , posterior to anterior normalized loads directed to the posterior calf with a ligament testing device . FINDINGS The loading protocol produced a measurable increase in displacement but not stiffness . Neither displacement nor stiffness measures however were affected by day of the menstrual cycle . No consistent relationships between hormonal concentrations and displacement or stiffness were evident . INTERPRETATION Following a controlled , static external load , displacement and stiffness were not affected differently by day of the menstrual cycle Background Women who participate in high-risk sports suffer anterior cruciate ligament injury at a 4- to 6-fold greater rate than men . Purpose To prospect ively determine if female athletes with decreased passive knee joint restraint ( greater joint laxity ) and greater side-to-side differences in knee laxity would be at increased risk of anterior cruciate ligament injury . Study Design Case control study ; Level of evidence , 3 . Methods From 1558 female soccer and basketball players who were prospect ively screened , 19 went on to tear their anterior cruciate ligaments . Four height- and mass-matched control subjects were selected from the uninjured screened athletes for comparison with each of the 19 injured subjects , making a total of 95 subjects ( 19 injured ; 76 uninjured ) . Generalized joint-laxity tests and anterior-posterior tibiofemoral translation were quantified using the CompuKT knee arthrometer . A multivariable logistic regression model was constructed to determine predictors of anterior cruciate ligament injury status from recorded laxity measures . Results A multivariable logistic regression model ( chi-square = 18.6 ; P = .002 ) used the independent variables laxity measures of knee hyperextension ( P = .02 ) , wrist and thumb to forearm opposition ( P = .80 ) , fifth-finger hyperextension > 90 ° ( P = .71 ) , side-to-side differences in anterior-posterior tibiofemoral translation ( P = .002 ) , and prior knee injury ( P = .22 ) to predict anterior cruciate ligament-injury status . The vali date d C statistic , or vali date d area under the receiver operating characteristic curve , was 0.72 . For every 1.3-mm increase in side-to-side differences in anterior-posterior knee displacement , the odds of anterior cruciate ligament – injured status increased 4-fold ( 95 % confidence interval , 1.68–9.69 ) . A positive measure of knee hyperextension increased the odds of anterior cruciate ligament-injured status 5-fold ( 95 % confidence interval , 1.24–18.44 ) . Conclusion The current results indicate that increased knee-laxity measures may contribute to increased risk of anterior cruciate ligament injury . The methods to quantify knee joint laxity in this report may be used in conjunction with measures of neuromuscular control of the knee joint to identify high-risk female athletes with high accuracy . Once high-risk female athletes are identified , they may be targeted to the appropriate interventions to reduce injury risk Background Despite research on the increased risk of anterior cruciate ligament tears in female athletes , few studies have addressed sex differences in the incidence of associated intraarticular injuries . Hypothesis When patients are stratified by sport and competition level , no sex differences exist in either the mechanism of injury or pattern of intraarticular injuries observed at  anterior cruciate ligament reconstruction .  Study Design Prospect i ve cohort study . Methods Two hundred twenty-one athletes undergoing anterior cruciate ligament reconstruction met our inclusion criteria of anterior cruciate ligament tear as a singular event without reinjury or history of prior injury or surgery in either knee . Data were collected on competition level ( high school , amateur ) , sport ( basketball , soccer , skiing ) , mechanism of injury , articular cartilage injuries , and meniscal tears . Data were statistically analyzed by sex with the chi-square test and Student 's t-test . Results High school athletes had no significant sex differences in mechanism of injury .  Female soccer athletes had fewer medial meniscal tears than did male athletes , and female basketball players had fewer medial femoral condyle injuries . At the amateur level , female basketball players had more contact injuries , an earlier onset of swelling , and fewer lateral meniscal tears than did male players . Conclusion At the high school level , male and female athletes shared a common mechanism of injury , and yet the female athletes had fewer intraarticular injuries in basketball and soccer . If such intraarticular injuries prove to be a significant risk factor for poor long-term outcome , women may enjoy a better prognosis after reconstruction Published reports agree that there is a strong associa tion between intercondylar notch stenosis and anterior cruciate ligament injuries . In a previously published retrospective study on bilateral anterior cruciate liga ment injuries and associated intercondylar notch ste nosis , we formulated the notch width index to measure and compare intercondylar notch width . The purpose of this prospect i ve study was to establish a normal range for the notch width index and to correlate inter condylar notch size and anterior cruciate ligament in juries . We gathered data on 902 high school athletes , including range of motion , thigh girth , ligament stability and intercondylar notch width using the notch width index .  The population was then followed prospect ively and anterior cruciate ligament injuries were recorded and correlated with notch width index in a blind manner . Two-year results showed that the overall anterior cru ciate ligament injury rate was 3 % . The normal intercon dylar notch ratio was 0.231 ± 0.044 . Intercondylar notch width index for men was larger than that for women . Athletes sustaining noncontact anterior cru ciate ligament tears have statistically significant inter condylar notch stenosis ( notch width index , 0.189 ) . Ten of 14 athletes with noncontact anterior cruciate liga ment injuries had a notch width index that was at least 1 SD below the mean . Athletes with contact anterior cruciate ligament injuries had a mean of 0.233 . We conclude that athletes with a stenotic intercondylar notch are at significantly greater risk for sustaining noncontact anterior cruciate ligament injury Background : The causes of noncontact anterior cruciate ligament injury remain an enigma . Purpose : To prospect ively evaluate risk factors for noncontact anterior cruciate ligament injuries in a large population of young athletic people . Study Design : Prospect i ve cohort study . Methods : In 1995 , 1198 new United States Military Academy cadets underwent detailed testing and many parameters were documented . During their 4-year tenure , all anterior cruciate ligament injuries that occurred were identified . Statistical analyses were used to identify the factors that may have predisposed the cadets to noncontact anterior cruciate ligament injuries . Results : Among the 895 cadets who completed the entire 4-year study , there were 24 noncontact anterior cruciate ligament tears ( 16 in men , 8 in women ) . Significant risk factors included small femoral notch width , generalized joint laxity , and , in women , higher than normal body mass index and KT-2000 arthrometer values that were 1 st and ard deviation or more above the mean . The presence of more than one of these risk factors greatly increased the relative risk of injury . All female cadets who had some combination of risk factors sustained noncontact anterior cruciate ligament injuries , indicating that some combinations of factors are especially perilous to the female knee . Conclusion : Several risk factors may predispose young athletes to noncontact anterior cruciate ligament injury Background Neuromuscular and proprioceptive training programs can decrease noncontact anterior cruciate ligament injuries ; however , they may be difficult to implement within an entire team or the community at large . Hypothesis A simple on-field alternative warm-up program can reduce noncontact ACL injuries . Study Design R and omized controlled trial ( clustered ) ; Level of evidence , 1 . Methods Participating National Collegiate Athletic Association Division I women 's soccer teams were assigned r and omly to intervention or control groups . Intervention teams were asked to perform the program 3 times per week during the fall 2002 season . All teams reported athletes ’ participation in games and practice s and any knee injuries . Injury rates were calculated based on athlete exposures , expressed as rate per 1000 athlete exposures . A z statistic was used for rate ratio comparisons . Results Sixty-one teams with 1435 athletes completed the study ( 852 control athletes ; 583 intervention ) . The overall anterior cruciate ligament injury rate among intervention athletes was 1.7 times less than in control athletes ( 0.199 vs 0.340 ; P = .198 ; 41 % decrease ) . Noncontact anterior cruciate ligament injury rate among intervention athletes was 3.3 times less than in control athletes ( 0.057 vs 0.189 ; P = .066 ; 70 % decrease ) . No anterior cruciate ligament injuries occurred among intervention athletes during practice versus 6 among control athletes ( P = .014 ) . Game-related noncontact anterior cruciate ligament injury rates in intervention athletes were reduced by more than half ( 0.233 vs 0.564 ; P = .218 ) . Intervention athletes with a history of anterior cruciate ligament injury were significantly less likely to suffer another anterior cruciate ligament injury compared with control athletes with a similar history ( P = .046 for noncontact injuries ) . Conclusion This program , which focuses on neuromuscular control , appears to reduce the risk of anterior cruciate ligament injuries in collegiate female soccer players , especially those with a history of anterior cruciate ligament injury Background The risk of subsequent anterior cruciate ligament injury  to either knee after surgery based on sex , age , and activity has not been extensively studied . Hypotheses Women have a higher incidence of anterior cruciate ligament injury to the contralateral knee after surgery than men but do not have a difference in injuries to the reconstructed knee . Young , competitive athletes have a higher incidence of injury than older patients . The time to return to full activities does not affect injury rate . Study Design Cohort study ( prognosis ) ; Level of evidence , 2 . Methods The authors prospect ively followed 1820 patients after primary anterior cruciate ligament reconstruction  to determine if patients suffered an injury to either knee within 5 years after surgery . Subsequent injury was evaluated based on sex , age , and activity level . Results Minimum 5-year follow-up was obtained on 1415 patients ( 78 % ) . Seventy-five patients ( 5.3 % ) had an injury to the contralateral knee , and 61 patients ( 4.3 % ) suffered an injury to the reconstructed knee ( P = . 2185 ) . Women suffered more injuries ( 7.8 % ) to the contralateral normal knee than men ( 3.7 % ; P < . 001 ) but not more injuries to the reconstructed knee ( 4.3 % vs 4.1 % ; P = . 5543 ) . The risk of subsequent injury to either knee was 17 % for patients < 18 years old , 7 % for patients aged 18 to 25 years , and 4 % for patients older than 25 years . There was no difference in injury rate between patients who returned before and after 6 months postoperatively . Conclusion Women have a higher incidence of anterior cruciate ligament injury to the contralateral knee than men after reconstruction . The incidence of injury to either knee after reconstruction is associated with younger age and higher activity level , but returning to full activities before 6 months postoperatively does not increase the risk of subsequent injury Background Female athletes participating in high-risk sports suffer anterior cruciate ligament injury at a 4- to 6-fold greater rate than do male athletes . Hypothesis Prescreened female athletes with subsequent anterior cruciate ligament injury will demonstrate decreased neuromuscular control and increased valgus joint loading , predicting anterior cruciate ligament injury risk . Study Design Cohort study ; Level of evidence , 2 . Methods There were 205 female athletes in the high-risk sports of soccer , basketball , and volleyball prospect ively measured for neuromuscular control using 3-dimensional kinematics ( joint angles ) and joint loads using kinetics ( joint moments ) during a jump-l and ing task . Analysis of variance as well as linear and logistic regression were used to isolate predictors of risk in athletes who subsequently ruptured the anterior cruciate ligament . Results Nine athletes had a confirmed anterior cruciate ligament rupture ; these 9 had significantly different knee posture and loading compared to the 196 who did not have anterior cruciate ligament rupture . Knee abduction angle ( P < . 05 ) at l and ing was 8 ° greater in anterior cruciate ligament-injured than in uninjured athletes . Anterior cruciate ligament-injured athletes had a 2.5 times greater knee abduction moment ( P < . 001 ) and 20 % higher ground reaction force ( P < . 05 ) , whereas stance time was 16 % shorter ; hence , increased motion , force , and moments occurred more quickly . Knee abduction moment predicted anterior cruciate ligament injury status with 73 % specificity and 78 % sensitivity ; dynamic valgus measures showed a predictive r2 of 0.88 . Conclusion Knee motion and knee loading during a l and ing task are predictors of anterior cruciate ligament injury risk in female athletes . Clinical Relevance Female athletes with increased dynamic valgus and high abduction loads are at increased risk of anterior cruciate ligament injury . The methods developed may be used to monitor neuromuscular control of the knee joint and may help develop simpler measures of neuromuscular control that can be used to direct female athletes to more effective , targeted interventions BACKGROUND Studies have suggested that exercise programs can reduce the incidence of noncontact injuries of the anterior cruciate ligament in female athletes . We conducted a two-year prospect i ve study to assess the effects of a knee ligament injury prevention exercise program on the incidence of noncontact anterior cruciate ligament injuries in high-school female athletes . METHODS A prospect i ve cohort design was used to study high-school female athletes ( playing soccer , basketball , and volleyball ) from fifteen schools ( 112 teams ) for two consecutive seasons . The schools were divided into treatment and control groups . The treatment group participated in a plyometric-based exercise program twice a week throughout the season . Practice and game exposures and compliance with the exercise program were recorded on a weekly basis . Suspected noncontact anterior cruciate ligament injuries were confirmed on the basis of the history as well as at the time of surgery and /or with magnetic resonance imaging . RESULTS A total of 1439 athletes ( 862 in the control group and 577 in the treatment group ) were monitored . There were six confirmed noncontact anterior cruciate ligament injuries : three in the treatment group , and three in the control group . The incidence of noncontact anterior cruciate ligament injuries per 1000 exposures was 0.167 in the treatment group and 0.078 in the control group , yielding an odds ratio of 2.05 , which was not significant ( p > 0.05 ) . CONCLUSIONS Our results suggest that a twenty-minute plyometric-based exercise program that focuses on the mechanics of l and ing from a jump and deceleration when running performed twice a week throughout the season will not reduce the rate of noncontact anterior cruciate ligament injuries in high-school female athletes The purpose of this study was to examine gender differences in the incidence of  anterior cruciate ligament ( ACL ) injuries in a population of high-level team h and ball players . We also wanted to examine injury mechanisms and possible risk factors for ACL injuries , including menstrual status . The study was done prospect ively during the 1993 - 94 , 1994 - 95 , and 1995 - 96 seasons . We found 28 ACL injuries , 23 among women ( incidence : 0.31 + /- 0.06 injuries per 1000 player hours ) and 5 among men ( 0.06 + /- 0.03 inj./1000 h ; P < 0.001 vs women ; risk ratio : 5.0 ) . Of the 28 injuries , 24 occurred during competition ( 0.91 + /- 0.19 inj./1000 h ; women : 1.60 + /- 0.35 inj./1000 h ; men : 0.23 + /- 0.13 inj./1000 h ; P < 0.001 vs. women ; risk ratio : 7.0 ) and 4 during training ( 0.03 + /- 0.02 inj./1000 h ; P < 0.001 vs. competition ; risk ratio : 29.9 ) . Nearly all the injuries ( n = 25 ) occurred in non-contact situations when the players performed high-speed plant- and -cut movements which they were well accustomed to . A reliable menstrual history could be obtained in 17 of the 23 cases among females . Five of the injuries occurred in the menstrual phase , 2 in the follicular phase , 1 in the early luteal phase and 9 in the late luteal phase ( chi-square3 d.f . = 13.2 ; P < 0.01 ) . The results suggest that there may be an increased risk of ACL injury during the week prior to or after the start of the menstrual period BACKGROUND Despite recent evidence supporting the use of neuromuscular training to reduce anterior cruciate ligament injury risk , female athletes continue to show an increased anterior cruciate ligament injury rate in collegiate basketball and soccer when compared to males . The purpose of the current study was to identify gender and task differences in measures that may increase the risk of anterior cruciate ligament injury in female basketball and soccer athletes . METHODS Eleven female and 11 male collegiate basketball and soccer athletes were height ( female mean 176 ( SD 8 cm ) , male mean 176 ( SD 8 cm ) ) and weight ( female mean 73 ( SD 7 kg ) , male mean 74 ( SD 6 kg ) ) matched .  Three-dimensional motion analysis was used to calculate differences in total coronal plane angular joint excursion ( maximum-minimum ) between male and female athletes when performing a series of medially and laterally directed drop l and ings . FINDINGS Female athletes demonstrated increased total coronal plane excursion for the hip , knee and ankle ( P < 0.05 ) during the medial drop l and ing . During the lateral drop l and ing females displayed increased excursion at the hip and knee . When comparing tasks , the lateral drop l and ing result ed in greater coronal plane excursion at the hip ( P < 0.05 ) while the knee showed no differences between movements . In contrast , females demonstrated increased ankle excursion during the medial drop task ( P < 0.05 ) . INTERPRETATION Female athletes demonstrate increased lower extremity coronal plane excursion when performing single leg drop l and ing in both the medial and lateral direction when compared to height/weight matched male athletes . This increased coronal plane oscillation of lower extremity joints may be related to the increased risk of anterior cruciate ligament injury for female basketball and soccer athletes Background Among female athletes it has not been established whether a neuromuscular and proprioceptive sports-specific training program will consistently reduce the incidence of anterior cruciate ligament injuries . Purpose To determine whether a neuromuscular and proprioceptive performance program was effective in decreasing the incidence of anterior cruciate ligament injury within a select population of competitive female youth soccer players . Study Design Cohort study ; Level of evidence , 2 . Methods In 2000 , 1041 female subjects from 52 teams received a sports-specific training intervention  in a prospect i ve non-r and omized trial . The control group consisted of the remaining 1905 female soccer players from 95 teams participating in the same league who were age and skill matched . In the 2001 season , 844 female athletes from 45 teams were enrolled in the study , with 1913 female athletes ( from 112 teams ) serving as the age- and skill-matched controls . All subjects were female soccer players between the ages of 14 and 18 and participated in either their traditional warm-up or a sports-specific training intervention before athletic activity over a 2-year period . The intervention consisted of education , stretching , strengthening , plyometrics , and sports-specific agility drills design ed to replace the traditional warm-up . Results During the 2000 season , there was an 88 % decrease in anterior cruciate ligament injury in the enrolled subjects compared to the control group . In year 2 , during the 2001 season , there was a 74 % reduction in anterior cruciate ligament tears in the intervention group compared to the age- and skill-matched controls . Conclusion Using a neuromuscular training program may have a direct benefit in decreasing the number of anterior cruciate ligament injuries in female soccer players Objective To identify a significant change in the laxity of the anterior cruciate ligament ( ACL ) in the competitive adolescent female athlete throughout the different phases of the menstrual cycle . Design Prospect i ve , single-blinded 8-week study set during a winter sports season . Setting Suburban Ohio Division I high school . Participants 26 members of gymnastics , soccer , track , tennis , and basketball teams . All participants were screened for normal menstrual cycles ( 26–30 days , menses 4–7 days long ) . Main Outcome Measures  KT-1000 arthrometer  was used to measure laxity by performing repeated measures throughout an 8-week period . Measurements were taken before the athletes ' workouts . The athlete charted the menstrual periods on a monthly calendar . The measurements were then grouped into the three phases of the menstrual cycle ( follicular , ovulatory , and luteal ) and averaged . Results Right knee laxity measured 4.98 mm follicular phase , 5.24 mm ovulatory , and 5.09 mm luteal . Left knee laxity measured 4.51 mm follicular , 4.43 mm ovulatory , and 4.62 mm luteal . There was no statistical difference among the three phases in the left ( p = 0.9 ) and right ( p = 0.7977 ) . Additionally , left ACL laxity was significantly less in all three phases . We found no statistically significant variability in laxity among the five sports sample d ( p > 0.63 to 0.10 ) and different ages ( p = 0.404 ) Conclusions We found an insignificant change in ACL laxity from follicular to luteal phases of the menstrual cycle . This indicates that no single phase of the menstrual cycle clinical ly affects the ACL more than the next . Although the presence of sex hormones — particularly estrogen — may indeed predispose females to higher ACL injury rates , we did not find any evidence that hormonal level changes equate with significant ACL laxity changes . We conclude that the menstrual cycle does not significantly affect ACL laxity in the competitive adolescent female athlete Background : Female athletes who participate in sports involving jumping and cutting maneuvers are up to eight times more likely to sustain a rupture of the anterior cruciate ligament than are men participating in the same sports . We tested the hypothesis that healthy young women are able to volitionally increase the apparent torsional stiffness of the knee , by maximally activating the knee muscles , significantly less than are size-matched men participating in the same type of sport . Methods : Twenty-four NCAA ( National Collegiate Athletic Association ) Division-I athletes ( twelve men and twelve women ) competing in sports associated with a high risk of injury to the anterior cruciate ligament ( basketball , volleyball , and soccer ) were compared with twenty-eight collegiate endurance athletes ( fourteen men and fourteen women ) participating in sports associated with a low risk of such injuries ( bicycling , crew , and running ) . Male and female pairs were matched for age , height , weight , body mass index , shoe size , and activity level . Testing was performed with a weighted pendulum that applied a medially directed 80-N impulse force to the lateral aspect of the right forefoot . The result ing internal rotation of the leg was measured optically , to the nearest 0.25 ° , at 30 ° and 60 ° of knee flexion , both with and without maximal activation of the knee muscles . Results : Maximal rotations of the leg were greater in women than in men in both the passive and the active muscle state ( 16 % and 27 % greater [ p = 0.01 and p = 0.02 ] , respectively ) . Moreover , female athletes exhibited a significantly ( 18 % ) smaller volitional increase in apparent torsional stiffness of the knee under internal rotation loading than did the matched male athletes ( p = 0.014 ) ; this was particularly the case for those who participated in sports involving jumping and pivoting maneuvers ( 42 % difference between genders , p = 0.001 ) . Conclusions : The collegiate female athletes involved in high-risk sports exhibited less muscular protection of the knee ligaments during external loading of the knee than did size and sport-matched male athletes . Clinical Relevance : Improving active muscle protection of the knee during training and rehabilitation might help to decrease rates of knee injury BACKGROUND Knee valgus load during sports movement is viewed as an important predictor of non-contact anterior cruciate ligament injury risk , particularly in females . Formulating movement strategies that can reduce valgus loading during these movements therefore appears pertinent to reducing anterior cruciate ligament injury rates . With this in mind , the current study examined the relationship between peak valgus moment and lower extremity postures at impact during a sidestep cutting task . METHODS Ten male and ten female NCAA athletes had initial contact three-dimensional hip , knee and ankle angles and subsequent knee valgus moment quantified  during the execution of ( n=10 trials ) sidesteps .  Peak valgus data were normalized to mass and height and tested for the main effect of gender ( ANOVA , P<0.05 ) . Intra-subject correlations between the eight initial joint angles and the normalized valgus moment were then conducted across the ten sidestepping trials . The ensuing slopes of regression were su bmi tted to a two- sample t-test to determine whether mean slope values were significantly different from zero and for the main effect of gender ( P<0.05 ) . FINDINGS Females had significantly larger normalized knee valgus moments than males . A greater peak valgus moment was associated with larger initial hip flexion and internal rotation , and with larger initial knee valgus angle . Peak knee valgus moment was more sensitive to initial hip internal rotation and knee valgus position in females . INTERPRETATION Training of neuromuscular control at the hip joint may reduce the likelihood of anterior cruciate ligament injury via a valgus loading mechanism during sidestepping , especially in females Background Altered motor control strategies in l and ing and jumping maneuvers are a potential mechanism of noncontact anterior cruciate ligament injury . There are biomechanical differences between male and female athletes in the l and ing phase of stop-jump tasks . Fatigue is a risk factor in musculoskeletal injuries . Hypothesis Lower extremity muscle fatigue alters the knee kinetics and kinematics during the l and ing phase of 3 stop-jump tasks and increases an athlete 's risk of anterior cruciate ligament injury . Study Design Controlled laboratory study . Methods Three-dimensional videography and force plate data were collected for 20 recreational athletes ( 10 male and 10 female athletes ) performing 3 stop-jump tasks before and after completing a fatigue exercise .  Knee joint angles and result ant forces and moments were calculated . Results Both male and female subjects had significantly increased peak proximal tibial anterior shear forces ( P = . 01 ) , increased valgus moments ( P = . 03 ) , and decreased knee flexion angles ( P = . 03 ) during l and ings of all 3 stop-jump tasks when fatigued . Fatigue did not significantly affect the peak knee extension moment for male or female athletes . Conclusion Fatigued recreational athletes demonstrate altered motor control strategies , which may increase anterior tibial shear force , strain on the anterior cruciate ligament , and risk of injury for both female and male subjects . Clinic Relevance Fatigued athletes may have an increased risk of noncontact anterior cruciate ligament injury Objective Incidence rate ( IR ) of an ipsilateral or contralateral injury after  anterior cruciate ligament reconstruction ( ACLR )  is unknown . The hypotheses were that the IR of anterior cruciate ligament ( ACL ) injury after ACLR would be greater than the IR in an uninjured cohort of athletes and would be greater in female athletes after ACLR than male athletes . Design Prospect i ve case – control study . Setting Regional sports community . Participants Sixty-three subjects who had ACLR and were ready to return to sport ( RTS ) and 39 control subjects . Independent Variables Second ACL injury and sex . Main Outcome Measures Second ACL injury and athletic exposure ( AE ) was tracked for 12 months after RTS . Sixteen subjects after ACLR and 1 control subject suffered a second ACL injury . Between- and within-group comparisons of second ACL injury rates ( per 1000 AEs ) were conducted . Results The IR of ACL injury after ACLR ( 1.82/1000 AE ) was 15 times greater [ risk ratio ( RR ) = 15.24 ; P = 0.0002 ) than that of control subjects ( 0.12/1000AE ) . Female ACLR athletes demonstrated 16 times greater rate of injury ( RR = 16.02 ; P = 0.0002 ) than female control subjects . Female athletes were 4 ( RR = 3.65 ; P = 0.05 ) times more likely to suffer a second ACL injury and 6 times ( RR = 6.21 ; P = 0.04 ) more likely to suffer a contralateral injury than male athletes . Conclusions An increased rate of second ACL injury after ACLR exists in athletes when compared with a healthy population . Female athletes suffer contralateral ACL injuries at a higher rate than male athletes and seem to suffer contralateral ACL injuries more frequently than graft re-tears . The identification of a high-risk group within a population of ACLR athletes is a critical step to improve outcome after ACLR and RTS Background Athletes who return to sport participation after anterior cruciate ligament reconstruction ( ACLR )  have a higher risk of a second anterior cruciate ligament injury ( either reinjury or contralateral injury ) compared with non — anterior cruciate ligament— injured athletes . Hypotheses Prospect i ve measures of neuromuscular control and postural stability after ACLR will predict relative increased risk for a second anterior cruciate ligament injury . Study Design Cohort study ( prognosis ) ; Level of evidence , 2 . Methods Fifty-six athletes underwent a prospect i ve biomechanical screening after ACLR using 3-dimensional motion analysis during a drop vertical jump maneuver and postural stability assessment before return to pivoting and cutting sports .  After the initial test session , each subject was followed for 12 months for occurrence of a second anterior cruciate ligament injury . Lower extremity joint kinematics , kinetics , and postural stability were assessed and analyzed . Analysis of variance and logistic regression were used to identify predictors of a second anterior cruciate ligament injury . Results Thirteen athletes suffered a subsequent second anterior cruciate ligament injury . Transverse plane hip kinetics and frontal plane knee kinematics during l and ing , sagittal plane knee moments at l and ing , and deficits in postural stability predicted a second injury in this population ( C statistic = 0.94 ) with excellent sensitivity ( 0.92 ) and specificity ( 0.88 ) . Specific predictive parameters included an increase in total frontal plane ( valgus ) movement , greater asymmetry in internal knee extensor moment at initial contact , and a deficit in single-leg postural stability of the involved limb , as measured by the Biodex stability system . Hip rotation moment independently predicted second anterior cruciate ligament injury ( C = 0.81 ) with high sensitivity ( 0.77 ) and specificity ( 0.81 ) . Conclusion Altered neuromuscular control of the hip and knee during a dynamic l and ing task and postural stability deficits after ACLR are predictors of a second anterior cruciate ligament injury after an athlete is released to return to sport Background : Noncontact anterior cruciate ligament injuries are among the most common injuries in sports medicine , and identification of risk factors for noncontact injury is an area of active research . Hypothesis : Evaluation of the femoral notch along the path of the anterior cruciate ligament may eluci date anatomical risk factors previously unseen on conventional images . Study Design : Case-control study ; Level of evidence , 3 . Methods : Twenty-seven patients with noncontact anterior cruciate ligament injuries were matched to healthy individuals for height , weight , age , and sex in this case-control study . Sagittal magnetic resonance images of the contralateral knee of the injured patients and r and omized knees of the healthy controls were digitally transformed for viewing along the plane of the anterior cruciate ligament and evaluated for abnormalities of femoral notch outlet shape . Femoral notch shape was also evaluated by computer-generated surface models of the knee . Results : A bone ridge was observed on the medial side of the anterior notch outlet , and increasing ridge thickness was strongly associated with noncontact anterior cruciate ligament injury ( 3.87 ± 2.17 mm in injured and 2.16 ±1.80 mm in controls ; P = .0014 ) . Anterior and posterior femoral notch outlet stenosis were both significantly associated with noncontact anterior cruciate ligament injury ( P = .0008 and .02 , respectively ) , although anterior outlet stenosis became nonsignificant when stratified by the presence of an anteromedial bone ridge . Finally , images directed through the femoral notch with the knee at 45 ° of flexion provided an unobstructed view for ridge detection that may be utilized in plain radiography . Conclusion : The presence and thickness of an anteromedial bone ridge in the femoral notch has been identified as a potential risk factor for noncontact anterior cruciate ligament injury . A biomechanical injury model involving the femoral notch ridge in anterior cruciate ligament tears is proposed in which the anterior cruciate ligament may be tented and stretched over the anteromedial notch ridge during knee valgus and internal tibial rotation ; alternatively , the anterior cruciate ligament may be impinged at the lateral anterior outlet wall during knee valgus and external tibial rotation . Further investigation to determine the origin of the bone ridges and the validity of the proposed injury model is recommended BACKGROUND It has been suggested that gender differences in the performance of athletic maneuvers is a contributory factor with respect to the disproportionate incidence of non-contact anterior cruciate ligament injury in female athletes . The purpose of this study was to evaluate gender differences in knee joint kinematics , kinetics and muscle activation during a side-step cutting . METHODS Three-dimensional kinematics , ground reaction forces ( 2400 Hz ) and electromyographic activity ( surface electrodes ) were recorded during the early deceleration phase of side-step cutting in 30 healthy collegiate soccer players ( 15 male , 15 female ) .  Gender differences in knee joint kinematics , peak moments , net joint moment impulse and average muscle EMG intensity were evaluated with one-tailed t-tests . FINDINGS No differences in kinematics were found . However , when compared to males , females demonstrated a smaller peak knee flexor moment ( 1.4 ( 0.8 ) vs. 2.1 ( 0.8 ) Nm/kg , P = 0.05 ) and a greater knee adductor moment ( 0.43 ( 0.5 ) vs. 0.01 ( 0.3 ) Nm/kg , P < 0.01 ) during early deceleration . In addition , females displayed greater average quadriceps EMG intensity than males ( 191 % vs. 151 % maximum voluntary isometric contraction , P = 0.02 ) . INTERPRETATION In general , females experienced increased frontal plane moments and decreased sagittal plane moments during early deceleration . These differences are suggestive of an " at risk " pattern in that frontal plane support of the knee is afforded primarily by passive structures ( including the anterior cruciate ligament ) . Furthermore , increased quadriceps activity and smaller net flexor moments may suggest less sagittal plane protection ( i.e. , increased tendency towards anterior tibial translation )
The clinical relevance of this finding is that female athletes may be more predisposed to anterior cruciate ligament injuries during the preovulatory phase of the menstrual cycle .
These findings may lead to potential interventions targeted toward this phase of the menstrual cycle to reduce the incidence of anterior cruciate ligament injury
Several theories have been proposed to explain the 3- to 6-fold gender difference in the incidence of anterior cruciate ligament injuries .
One potential theory for the increased incidence is based on gender-related hormonal differences between men and women , especially after puberty and the onset of menses in the female athlete .
The purpose of this systematic review was to compile and systematic ally analyze the published literature to determine if the menstrual cycle is associated with anterior cruciate ligament injury risk and to provide an objective comparison of the published results .