***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: The purpose of this study was to compare the ACL injury rate between two different floor types - wooden floors ( parquet , generally having lower friction ) and artificial floors ( generally having higher friction ) . ACL injuries have been recorded prospect ively from the three top divisions for men and women in Norwegian team h and ball during seven seasons ( 1989 - 2000 ) . A total of 174 ACL injuries have been recorded , and of these 53 occurred in regular league games . The floor types for all regular games from the same seasons have been determined retrospectively based on match schedules . The matches were divided into two groups : those played on wooden floors and those played on artificial floors . A total of nine injuries  occurred among men ( incidence : 0.24+/-0.09 injuries per 1000 player hours ) and 44 among women ( 0.77+/-0.04 injuries 1000 h(-1 ) ; OR vs. men : 3.21 ( 1.56 - 6.58 ) ; P=0.001 ) . Among men , four injuries occurred on wooden floors ( 0.32+/-0.13 injuries 1000 h(-1 ) ) and five injuries occurred on artificial floors ( 0.20+/-0.12 injuries 1000 h(-1 ) ; OR vs. wooden floors : 0.63 ( 0.17 - 2.37 ) ; ns ) . Among women , eight injuries occurred on wooden floors ( 0.41+/-0.09 injuries 1000 h(-1 ) ; OR vs. men : 1.29 ( 0.39 - 4.28 ) ; ns ) and 36 on artificial floors ( 0.96+/-0.04 injuries 1000 h(-1 ) ; OR vs. wooden floors : 2.35 ( 1.09 - 5.07 ) ; P=0.03 ; OR vs. men : 4.77 ( 1.87 - 12.18 ) ; P=0.001 ) . These results indicate that the risk of ACL injury for women is higher on artificial floors than on wooden floors Background In sports involving pivoting and l and ing , female athletes suffer knee injury at a greater rate than male athletes . Hypotheses Proprioceptive deficits in control of the body 's core may affect dynamic stability of the knee . Female , but not male , athletes who suffered a knee injury during a 3-year follow-up period would demonstrate decreased core proprioception at baseline testing as compared with uninjured athletes . Study Design Cohort study ( prognosis ) ; Level of evidence , 2 . Methods Study subjects were 277 collegiate athletes ( 140 female , 137 male ) who were prospect ively tested for core proprioception by active and passive proprioceptive repositioning .  Athletes were monitored for injury for 3 years . An ANOVA and multivariate logistic regression were used to test whether core proprioception was related to knee injuries in athletes . Results Twenty-five athletes sustained knee injuries ( 11 women , 14 men ) . Deficits in active proprioceptive repositioning were observed in women with knee injuries ( 2.2 ° ) and ligament/meniscal injuries ( 2.4 ° ) compared with uninjured women ( 1.5 ° , P ≤ .05 ) . There were no differences in average active proprioceptive repositioning error between injured men and uninjured men ( P ≥ .05 ) . Uninjured women demonstrated significantly less average error in active proprioceptive repositioning than uninjured men ( 1.5 ° vs 1.7 ° , P ≤ .05 ) . For each degree increase in average active proprioceptive repositioning error , a 2.9-fold increase in the odds ratio of knee injury was observed , and a 3.3-fold increase in odds ratio of ligament/meniscal injury was observed ( P ≤ .01 ) . Active proprioceptive repositioning predicted knee injury status with 90 % sensitivity and 56 % specificity in female athletes . Conclusions Impaired core proprioception , measured by active proprioceptive repositioning of the trunk , predicted knee injury risk in female , but not male , athletes Purpose The goal of this study was to document the incidence of anterior cruciate ligament ( ACL ) tears and possible risk factors for these injuries in a large population of young , athletic subjects . Methods The authors retrospectively review ed the US Naval Academy ’s data base of midshipmen admitted in 1999 and 2000 ( n = 2,345 ) and prospect ively followed until graduation 4 years later or disenrollment . Excluded were 658 who had a history of preadmission ACL injury or surgery , those without initial radiographs or documented baseline height and weight , or those who had documented contact ACL injuries . Therefore , 1,687 subjects comprised the study group .  St and ard radiographic measurements , including condylar width , notch width , and femoral notch width index ( notch width divided by condyle width ) , were obtained for all subjects . Statistical analyses were used to determine differences between injured and uninjured subjects . Results The overall incidence of non-contact ACL injury was 2.9 % ( 37 men , 12 women ) . The average BMI was 25.6 and 24.4 kg/m2 for the injured and uninjured groups , respectively ( P < 0.05 ) . Although femoral notch width alone was not associated with non-contact ACL injuries , subjects with higher than average BMI in combination with narrow notch width were at significant risk for ACL injury ( P = 0.021 ) . Conclusions Elevated BMI combined with narrow notch width may predispose young athletes to non-contact ACL injury . Level of evidence Retrospective comparative study , Level III The objective of this study was to investigate regional differences in injury incidence in men 's professional football in Europe . A nine-season prospect i ve cohort study was carried out between 2001 - 2002 and 2009 - 2010 involving 1357 players in 25 teams from nine countries . Teams were categorized into different regions according to the Köppen-Geiger climate classification system . Teams from the northern parts of Europe ( n = 20 ) had higher incidences of injury overall [ rate ratio 1.12 , 95 % confidence interval ( CI ) 1.06 to 1.20 ] , training injury ( rate ratio 1.16 , 95 % CI 1.05 to 1.27 ) , and severe injury ( rate ratio 1.29 , 95 % CI 1.10 to 1.52 ) , all statistically significant , compared to teams from more southern parts ( n = 5 ) . In contrast , the anterior cruciate ligament injury incidence was lower in the northern European teams with a statistically significant difference ( rate ratio 0.43 , 95 % CI 0.25 to 0.77 ) , especially for noncontact anterior cruciate ligament injury ( rate ratio 0.19 , 95 % CI 0.09 to 0.39 ) . In conclusion , this study suggests that there are regional differences in injury incidence of European professional football . However , further studies are needed to identify the underlying causes Background No prospect i ve surveillance system exists for monitoring the outcome of cruciate ligament surgery . Purpose This article is intended to describe the development and procedures of the Norwegian National Knee Ligament Registry ( NKLR ) , including baseline results from the first 2 years of operation . Study Design Cohort study ( prevalence ) ; Level of evidence , 1 . Methods The NKLR was established on June 7 , 2004 to collect information prospect ively on all cases of cruciate ligament reconstruction surgery in Norway . Information on the details of surgery is gathered through a registration form completed by the surgeon postoperatively , and a vali date d knee outcome score form is completed by the patients preoperatively and at follow-ups on all patients at 2 , 5 , and 10 years postoperatively . Hospital compliance was examined in 2005 and 2006 . Results A total of 2793 primary cruciate ligament reconstruction surgeries were registered by 57 hospitals . This corresponds to an annual population incidence of primary anterior cruciate ligament reconstruction surgeries of 34 per 100 000 citizens ( 85 per 100 000 citizens in the main at-risk age group of 16–39 years ) . After 21 months of operation , the NKLR had an overall compliance of 97 % when compared with the hospital records . Conclusions A national population -based cruciate ligament registry has been developed , implemented , and maintained in Norway . The registry will each year enroll approximately 1500 primary cruciate ligament reconstruction cases . It is expected that inadequate procedures and devices can be identified , as well as prognostic factors associated with good and poor outcomes , at least for the most frequent categories Objective : To compare the incidence , nature , severity and cause of match injuries sustained on  grass  and  new generation artificial turf by male and female footballers . Methods : The National Collegiate Athletic Association Injury Surveillance System was used for a two-season ( August to December ) prospect i ve study of American college and university football teams ( 2005 season : men 52 teams , women 64 teams ; 2006 season : men 54 teams , women 72 teams ) . Injury definitions and recording procedures were compliant with the international consensus statement for epidemiological studies of injuries in football . Athletic trainers recorded details of the playing surface and the location , diagnosis , severity and cause of all match injuries . The number of days lost from training and match play was used to define the severity of an injury . Match exposures ( player hours ) were recorded on a team basis . Results : The overall incidence of match injuries for men was 25.43 injuries/1000 player hours on artificial turf and 23.92 on grass ( incidence ratio 1.06 ; p = 0.46 ) and for women was 19.15 injuries/1000 player hours on artificial turf and 21.79 on grass ( incidence ratio = 0.88 ; p = 0.16 ) . For men , the mean severity of non-season ending injuries was 7.1 days ( median 5 ) on artificial turf and 8.4 days ( median 5 ) on grass and , for women , 11.2 days ( median 5 ) on artificial turf and 8.9 days ( median 5 ) on grass . Joint (non-bone)/ligament/cartilage and contusion injuries to the lower limbs were the most common general categories of match injury on artificial turf and grass for both male and female players . Most injuries were acute ( men : artificial turf 24.60 , grass 22.91 ; p = 0.40 ; women : artificial turf 18.29 , grass 20.64 ; p = 0.21 ) and result ed from player-to-player contact ( men : artificial turf 14.73 , grass 13.34 ; p = 0.37 ; women : artificial turf 10.72 ; grass 11.68 ; p = 0.50 ) . Conclusions : There were no major differences in the incidence , severity , nature or cause of match injuries sustained on new generation artificial turf and grass by either male or female players Objective : To assess the contribution of ground variables including grass type to the rate of anterior cruciate ligament ( ACL ) injury in the Australian Football League ( AFL ) , specifically which factors are primarily responsible for previously observed warm season and early season biases for ACL injuries . Methods :  Grass types used at the major AFL venues from 1992 to 2004 were established by consultation with ground managers , and ground hardness and other weather variables were measured prospect ively . Results : There were 115 ACL injuries occurring in matches during the survey time period , 88 with a non-contact mechanism . In multivariate analysis , use of bermuda ( couch ) grass as opposed to rye grass , higher grade of match , and earlier stage of the season were independent risk factors for non-contact ACL injury . Ground hardness readings did not show a significant association with ACL injury risk , whereas weather variables of high evaporation and low prior rainfall showed univariate association with injury risk but could not be entered into a logistic regression equation . Discussion : Rye grass appears to offer protection against ACL injury compared with bermuda ( couch ) grass fields . The likely mechanism is reduced “ trapping ” of football boots by less thatch . Grass species as a single consideration can not fully explain the ACL early season bias , but is probably responsible for the warm season bias seen in the AFL . Weather variables previously identified as predictors are probably markers for predominance of bermuda over rye grass in mixed fields 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 non 
    Output:
    
Results The principal findings of this systematic review related to the risk factors for ACL injury in male athletes are : ( 1 ) most of the evidence is related to environmental and anatomical risk factors ; ( 2 ) dry weather conditions may increase the risk of non-contact ACL injuries in male athletes ; ( 3 ) artificial turf may increase the risk of non-contact ACL injuries in male athletes ; ( 4 ) higher posterior tibial slope of the lateral tibial plateau may increase the risk of non-contact ACL injuries in male athletes .
Conclusion Anterior cruciate ligament injury in male athletes likely has a multi-factorial aetiology .
There is a lack of evidence regarding neuromuscular and biomechanical risk factors for ACL injury in male athletes .