***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background Neuromuscular training may reduce risk factors that contribute to ACL injury incidence in female athletes . Multi-component , ACL injury prevention training programs can be time and labor intensive , which may ultimately limit training program utilization or compliance . The purpose of this study was to determine the effect of neuromuscular training on those classified as " high-risk " compared to those classified as " low-risk . " The hypothesis was that high-risk athletes would decrease knee abduction moments while low-risk and control athletes would not show measurable changes . Methods Eighteen high school female athletes participated in neuromuscular training 3 ×  /week over a 7-week period . Knee kinematics and kinetics were measured during a drop vertical jump ( DVJ ) test at pre/post training . External knee abduction moments were calculated using inverse dynamics . Logistic regression indicated maximal sensitivity and specificity for prediction of ACL injury risk using external knee abduction ( 25.25 Nm cutoff ) during a DVJ . Based on these data , 12 study subjects ( and 4 controls ) were grouped into the high-risk ( knee abduction moment > 25.25 Nm ) and 6 subjects ( and 7 controls ) were grouped into the low-risk ( knee abduction < 25.25 Nm ) categories using mean right and left leg knee abduction moments . A mixed design repeated measures ANOVA was used to determine differences between athletes categorized as high or low-risk . Results Athletes classified as high-risk decreased their knee abduction moments by 13 % following training ( Dominant pre : 39.9 ± 15.8 Nm to 34.6 ± 9.6 Nm ; Non-dominant pre : 37.1 ± 9.2 to 32.4 ± 10.7 Nm ; p = 0.033 training X risk factor interaction ) . Athletes grouped into the low-risk category did not change their abduction moments following training ( p > 0.05 ) . Control subjects classified as either high or low-risk also did not significantly change from pre to post-testing . Conclusion These results indicate that " high-risk " female athletes decreased the magnitude of the previously identified risk factor to ACL injury following neuromuscular training . However , the mean values for the high-risk subjects were not reduced to levels similar to low-risk group following training . Targeting female athletes who demonstrate high-risk knee abduction loads during dynamic tasks may improve efficacy of neuromuscular training . Yet , increased training volume or more specific techniques may be necessary for high-risk athletes to substantially decrease ACL injury risk Background : Previous studies have found significant predictors for functional outcome after anterior cruciate ligament ( ACL ) reconstruction ; however , studies examining predictors for functional outcome in nonoperatively treated individuals are lacking . Hypothesis : Single-legged hop tests predict self-reported knee function ( International Knee Documentation Committee [ IKDC ] 2000 ) in nonoperatively treated ACL-injured individuals 1 year after baseline testing . Study Design : Cohort study ( prognosis ) ; Level of evidence , 2 . Methods : Ninety-one nonoperatively treated patients with an ACL injury were tested using 4 single-legged hop tests on average 74 ± 30 days after injury in a prospect i ve cohort study . Eighty-one patients ( 89 % ) completed the IKDC 2000 1 year later . Patients with an IKDC 2000 score equal to or higher than the age- and gender-specific 15th percentile score from previously published data on an uninjured population were classified as having self-reported function within normal ranges . Logistic regression analyses were performed to identify predictors of self-reported knee function . The area under the curve ( AUC ) from receiver operating characteristic curves was used as a measure of discriminative accuracy . Optimal limb symmetry index ( LSI ) cutoff for the best single-legged hop test was defined as the LSI with the highest product of sensitivity and specificity . Results : Single hop for distance symmetry indexes predicted self-reported knee function at the 1-year follow-up ( P = .036 ) . Combinations of any 2 hop tests ( AUC = 0.64 - 0.71 ) did not give a higher discriminative accuracy than the single hop alone ( AUC = 0.71 ) . A cutoff of 88 % ( LSI ) for the single hop revealed a sensitivity of 71.4 % and a specificity of 71.7 % . Conclusion : The single hop for distance ( LSI ) significantly predicted self-reported knee function after 1 year in nonoperatively treated ACL-injured patients . Combinations of 2 single-legged hop tests did not lead to higher discriminative accuracy than the single hop alone 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 : The incidence of second anterior cruciate ligament ( ACL ) injuries in the first 12 months after ACL reconstruction ( ACLR )  and return to sport ( RTS ) in a young , active population has been reported to be 15 times greater than that in a previously uninjured cohort . There are no reported estimates of whether this high relative rate of injury continues beyond the first year after RTS and ACLR . Hypothesis : The incidence rate of a subsequent ACL injury in the 2 years after ACLR and RTS would be less than the incidence rate reported within the first 12 months after RTS but greater than the ACL injury incidence rate in an uninjured cohort of young athletes . Study Design : Cohort study ; Level of evidence , 2 . Methods : Seventy-eight patients ( mean age , 17.1 ± 3.1 years ) who underwent ACLR and were ready to return to a pivoting/cutting sport and 47 controls ( mean age , 17.2 ± 2.6 years ) who also participated in pivoting/cutting sports were prospect ively enrolled . Each participant was followed for injury and athlete exposure ( AE ) data for a 24-month period after RTS . Twenty-three ACLR and 4 control participants suffered an ACL injury during this time . Incidence rate ratios ( IRRs ) were calculated to compare the rates ( per 1000 AEs ) of ACL injury in athletes in the ACLR and control groups . 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 AEs ) was nearly 6 times greater ( IRR , 5.71 ; 95 % CI , 2.0 - 22.7 ; P = .0003 ) than that in healthy control participants ( 0.24/1000 AEs ) . The rate of injury within 24 months of RTS for female athletes in the ACLR group was almost 5 times greater ( IRR , 4.51 ; 95 % CI , 1.5 - 18.2 ; P = .0004 ) than that for female controls . Although only a trend was observed , female patients within the ACLR group were twice as likely ( IRR , 2.43 ; 95 % CI , 0.8 - 8.6 ) 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 a retear injury of the ipsilateral graft . There was a trend toward a higher proportion of female participants ( 23.7 % ) who suffered a contralateral injury compared with male participants ( 10.5 % ) ( P = .18 ) . Conversely , for ipsilateral injuries , the incidence proportion between female ( 8.5 % ) and male ( 10.5 % ) participants was similar . Conclusion : These data support the hypothesis that in the 24 months after ACLR and RTS , patients are at a greater risk to suffer a subsequent ACL injury compared with young athletes without a history of ACL injuries . In addition , the contralateral limb of female patients appears at greatest risk PURPOSE The aim of this study was to determine the rates of contralateral anterior cruciate ligament ( ACL ) rupture and of ACL graft rupture after  ACL reconstruction  using either patellar tendon or hamstring tendon autograft , and to identify any patient characteristics that may increase this risk . TYPE OF STUDY Case series . METHODS Over a 2-year period , 760 endoscopic ACL reconstructions were performed in 743 patients .  Bone-patellar tendon-bone autograft was used in 316 patients and 4-str and hamstring tendon in 427 patients . Those patients with a previous contralateral ACL rupture or those who underwent a simultaneous bilateral ACL reconstruction were excluded , leaving 675 knees ( 675 patients ) for review . Persons not involved in the index operation or the care of the patient conducted follow-up assessment by telephone interview conducted 5 years after surgery . Patients were question ed about the incidence of ACL graft rupture , contralateral ACL rupture , symptoms of instability or significant injury , family history of ACL injury , and activity level according to the International Knee Documentation Committee scale . From our prospect i ve data base we obtained further information on graft source , meniscal or articular surface injury , and gender . Binary logistic regression was used to measure the relative association between the measured variables and the risk of graft rupture and contralateral ACL rupture . RESULTS Five years after primary ACL reconstruction , 612 of the 675 patients ( 90.7 % ) were assessed . ACL graft rupture occurred in 39 patients ( 6 % ) and contralateral ACL rupture occurred in 35 patients ( 6 % ) . Three patients suffered both a graft rupture and a contralateral ACL injury . The odds of ACL graft rupture were increased 3-fold by a contact mechanism of initial injury . Return to level 1 or 2 sports increased the risk of contralateral ACL injury by a factor of 10 . The risk of sustaining an ACL graft rupture was greatest in the first 12 months after reconstruction . No other studied variable increased the risk of repeat ACL injury . CONCLUSIONS After reconstruction , repeat ACL injury occurred in 12 % of patients over 5 years . Twelve months after reconstruction , the ACL graft is at no greater risk than the contralateral ACL , suggesting that adequate graft and muscular function for most activities is achieved by this time . Risk factors for repeat ACL injury identified included a return to competitive side-stepping , pivoting , or jumping sports , and the contact mechanism of the index injury . Female patients were at no greater risk of repeat ACL injury than male patients and graft choice did not affect the rate of repeat ACL injury . LEVEL OF EVIDENCE Level IV , case series Background : Tearing an anterior cruciate ligament ( ACL ) graft is a devastating occurrence after ACL reconstruction ( ACLR ) . Identifying and underst and ing the independent predictors of ACLR graft failure is important for surgical planning , patient counseling , and efforts to decrease the risk of graft failure . Hypothesis : Patient and surgical variables will predict graft failure after ACLR . Study Design : Prospect i ve cohort study . Methods : A multicenter group initiated a cohort study in 2002 to identify predictors of ACLR outcomes , including graft failure . First , to control for confounders , a single surgeon ’s data ( n = 281 ACLRs ) were used to develop a multivariable regression model for ACLR graft failure . Evaluated variables were graft type ( autograft vs allograft ) , sex , age , body mass index , activity at index injury , presence of a meniscus tear , and primary versus revision reconstruction . Second , the model was vali date d with the rest of the multicenter study ’s data ( n = 645 ACLRs ) to evaluate the generalizability of the model . Results : Patient age and ACL graft type were significant predictors of graft failure for all study surgeons . Patients in the age group of 10 to 19 years had the highest percentage of graft failures . The odds of graft rupture with an allograft reconstruction are 4 times higher than those of autograft reconstructions . For each 10-year 
    Output:
    
Conclusion : This systematic review and meta- analysis demonstrates that younger age and a return to high level of activity are salient factors associated with secondary ACL injury .
These data indicate that activity modification , improved rehabilitation and return-to-play guidelines , and the use of integrative neuromuscular training may help athletes more safely reintegrate into sport and reduce second injury in this at-risk population