A prospective cohort study of anterior cruciate ligament injuries in elite Norwegian team handball. Relationship of the menstrual cycle phase to anterior cruciate ligament injuries in teenaged female athletes Intraarticular Injuries Associated with Anterior Cruciate Ligament Tear: Findings at Ligament Reconstruction in High School and Recreational Athletes A Randomized Controlled Trial to Prevent Noncontact Anterior Cruciate Ligament Injury in Female Collegiate Soccer Players The Effects of Generalized Joint Laxity on Risk of Anterior Cruciate Ligament Injury in Young Female Athletes The Menstrual Cycle, Sex Hormones, and Anterior Cruciate Ligament Injury. The Relationship Between Intercondylar Notch Width of the Femur and the Incidence of Anterior Cruciate Ligament Tears Risk Factors Associated with Noncontact Injury of the Anterior Cruciate Ligament Prevention of Anterior Cruciate Ligament Injuries in Female Team Handball Players: A Prospective Intervention Study Over Three Seasons 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. Anterior Cruciate Ligament Injury and Reconstruction Among University Students Incidence of Contralateral and Ipsilateral Anterior Cruciate Ligament (ACL) Injury After Primary ACL Reconstruction and Return to Sport A comparison of dynamic coronal plane excursion between matched male and female athletes when performing single leg landings. Return to Basketball and Soccer After Anterior Cruciate Ligament Reconstruction in Competitive School-Aged Athletes The influence of gender on knee kinematics, kinetics and muscle activation patterns during side-step cutting. Risk Factors for Anterior Cruciate Ligament Injury
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 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 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 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 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 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 For 714 consecutive patients who underwent autogenous patellar tendon graft anterior cruciate ligament reconstructions  we intraoperatively measured intercondylar notch width . We prospect ively recorded height , weight , sex , and which patients subsequently tore their contralateral anterior cruciate ligament or the 10-mm autograft . The patients were divided into two groups based on notch width ( group 1 , 15 mm ; group 2 , 16 mm ) . The mean notch width was 13.9 2.2 mm for women and 15.9 2.5 mm for men . There was no statistically significant difference in notch width between height groups for women or men . Analysis showed that , with height and weight as covariates , women had statistically significantly narrower notches than men . Twenty-three of 388 patients in group 1 and 4 of 326 patients in group 2 tore their contralateral anterior cruciate ligaments . Within groups , no statistically significant differences in contralateral tear rates existed between men and women . Once the men and women had reconstructions with equally sized 10-mm autografts , there was no difference in graft tear rate between groups or between men and women . Our results show that patients with narrower notches have a higher incidence of tearing their contralateral anterior cruciate ligament . After reconstruction with a 10-mm autograft , the incidence of graft rupture is the same for men and women 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 Objective To assess the effect of a neuromuscular training program on the incidence of anterior cruciate ligament injuries in female team h and ball players . Design Prospect i ve intervention study . Setting Female team h and ball : Division I – III in Norway . Participants Players from the three top divisions : control season ( 1998–1999 ) , 60 teams ( 942 players ) ; first intervention season ( 1999–2000 ) , 58 teams ( 855 players ) ; second intervention season ( 2000–2001 ) , 52 teams ( 850 players ) . InterventionA five-phase program ( duration , 15 min ) with three different balance exercises focusing on neuromuscular control and planting/l and ing skills was developed and introduced to the players in the autumn of 1999 and revised before the start of the season in 2000 . The teams were instructed in the program and supplied with an instructional video , poster , six balance mats , and six wobble boards . Additionally , a physical therapist was attached to each team to follow up with the intervention program during the second intervention period . Main Outcome Measures The number of anterior cruciate ligament injuries during the three seasons and compliance with the program . Results There were  29 anterior cruciate ligament injuries  during the control season , 23 injuries during the first intervention season ( OR , 0.87 ; CI , 0.50–1.52 ; p = 0.62 ) , and 17 injuries during the second intervention season ( OR , 0.64 ; CI , 0.35–1.18 ; p = 0.15 ) . In the elite division , there were 13 injuries during the control season , six injuries during the first intervention season ( OR , 0.51 ; CI , 0.19–1.35 ; p = 0.17 ) , and five injuries in the second intervention season ( OR , 0.37 ; CI , 0.13–1.05 ; p = 0.06 ) . For the entire cohort , there was no difference in injury rates during the second intervention season between those who complied and those who did not comply ( OR , 0.52 ; CI , 0.15–1.82 ; p = 0.31 ) . In the elite division , the risk of injury was reduced among those who completed the anterior cruciate ligament injury prevention program ( OR , 0.06 ; CI , 0.01–0.54 ; p = 0.01 ) compared with those who did not . Conclusions This study shows that it is possible to prevent anterior cruciate ligament injuries with specific neuromuscular training 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 consequences of athletic injuries extend beyond the musculoskeletal system . Depression , anger , and tension have been observed in athletes with athletic injuries . It was hypothesized that among student athletes , the psychologic impact of injury may be seen as a drop in academic performance . Thirty-eight students who had an anterior cruciate ligament injury and subsequent reconstruction were evaluated retrospectively by academic transcript and question naire to measure their academic performance before their injury , in the semester of their injury , and in the semester after their surgery . The patients were compared with r and omly selected undergraduate control subjects . To evaluate any effect of the timing of the surgery on academic performance , the patients were separated into two groups , according to the timing of their reconstruction : those who had surgery during the academic semester , and those who elected to wait for a school break . There was a significant drop in grade point average of 0.3 grade points during the semester of injury among all injured students . Compared with those who had surgery during a break , the students who had surgery during the semester received more frequently the grade of failure ( 6 % versus 0 % ) or incomplete ( 33 % versus 9 % ) . These students also missed more school days ( 10.5 days versus 1.5 days ) and examinations ( 2.2 examinations versus 0.1 examinations ) . Only 47 % of students who had surgery during the semester were satisfied with their decision for surgical timing , compared with 96 % satisfied with the timing during an academic break . Acute anterior cruciate ligament rupture , and surgical reconstruction during an academic semester , have a significant academic effect in university students 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 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 : Little is known about the return to sports after  anterior cruciate ligament reconstruction  and whether sex differences exist regarding the level and timing at which athletes return . Hypotheses : Compared to school-aged girls , boys return to full sports earlier and at a higher frequency after surgery ( 1 ) . Athletes who return to sports earlier will not have a higher incidence of subsequent injury to either knee after surgery ( 2 ) . Study Design : Cohort . Methods : The patient population comprised 413 consecutive school-aged athletes who were injured while competing in basketball or soccer . Patients were enrolled prospect ively , and activity levels were obtained through follow-up visits , surveys , phone calls , and e-mail . Results : Follow-up was obtained for 402 patients ( basketball : 58 boys , 242 girls ; soccer : 25 boys , 77 girls ) . Eighty-seven percent of girls and boys returned to high school basketball after surgery : the mean time to return to full participation in basketball was 5.2 ± 2.1 months for girls and 5.3 ± 2.2 months for boys ( P = .92 ) . Similarly , 93 % of girls and 80 % of boys returned to compete in high school soccer after surgery ( P = .13 ) ; the mean time to return to full participation in soccer was 5.1 ± 1.9 months for girls and 5.1 ± 2.0 for boys ( P = 1.00 ) . About 20 % of athletes went on to compete in their sport in college . The time of return to sports was not a statistically significant factor for the incidence of subsequent anterior cruciate ligament injury . Conclusion : Of 402 athletes competing in basketball and soccer , women and men returned at the same rate and same level of sport after surgery . Athletes who returned to sports at earlier times after surgery did not have a higher incidence of subsequent anterior cruciate ligament injury than patients who returned at later times 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 ) Context : Injuries to the anterior cruciate ligament ( ACL ) of the knee are immediately debilitating and can cause long-term consequences , including the early onset of osteoarthritis . It is important to have a comprehensive underst and ing of all possible risk factors for ACL injury to identify individuals who are at risk for future injuries and to provide an appropriate level of counseling and programs for prevention . Objective : This review , part 1 of a 2-part series , highlights what is known and still unknown regarding anatomic and neuromuscular risk factors for injury to the ACL from the current peer- review ed literature . Data Sources : Studies were identified from MEDLINE ( 1951–March 2011 ) using the MeSH terms anterior cruciate ligament , knee injury , and risk factors . The bibliographies of relevant articles and review s were cross-referenced to complete the search . Study Selection : Prognostic studies that utilized the case-control and prospect i ve cohort study design s to evaluate risk factors for ACL injury were included in this review . Results : A total of 50 case-control and prospect i ve cohort articles were included in the review , and 30 of these studies focused on neuromuscular and anatomic risk factors . Conclusions : Several anatomic and neuromuscular risk factors are associated with increased risk of suffering ACL injury — such as female sex and specific measures of bony geometry of the knee joint , including decreased intercondylar femoral notch size , decreased depth of concavity of the medial tibial plateau , increased slope of the tibial plateaus , and increased anterior-posterior knee laxity . These risk factors most likely act in combination to influence the risk of ACL injury ; however , multivariate risk models that consider all the aforementioned risk factors in combination have not been established to explore this interaction
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 .