Patient demographic and surgical characteristics in anterior cruciate ligament reconstruction: a description of registries from six countries.

OBJECTIVE: Findings from individual anterior cruciate ligament reconstruction (ACLR) registry studies are impactful, but how various registries from different countries compare with different patient populations and surgical techniques has not been described. We sought to describe six ACLR registry cohorts to understand variation across countries. METHODS: Five European registries and one US registry participated. For each registry, all primary ACLR registered between registry establishment through 31December 2014 were identified. Descriptive statistics included frequencies, proportions, medians and IQRs. Revision incidence rates following primary ACLR were computed. RESULTS: 101 125 ACLR were included: 21 820 in Denmark, 300 in Luxembourg, 17 556 in Norway, 30 422 in Sweden, 2972 in the UK and 28 055 in the US. In all six cohorts, males (range: 56.8%-72.4%) and soccer injuries (range: 14.1%-42.3%) were most common. European countries mostly used autografts (range: 93.7%-99.7%); allograft was most common in the US (39.9%). Interference screw was the most frequent femoral fixation in Luxembourg and the US (84.8% and 42.9%), and suspensory fixation was more frequent in the other countries (range: 43.9%-75.5%). Interference was the most frequent tibial fixation type in all six cohorts (range: 64.8%-98.2%). Three-year cumulative revision probabilities ranged from 2.8% to 3.7%. CONCLUSIONS: Similarities in patient demographics and injury activity were observed between all cohorts of ACLR. However, graft and fixation choices differed. Revision rates were low. This work, including >100 000 ACLR, is the most comprehensive international description of contemporary practice to date.

Patients With Concomitant Intra-articular Lesions at Index Surgery Deteriorate in Their Knee Injury and Osteoarthritis Outcome Score in the Long Term More Than Patients With Isolated Anterior Cruciate Ligament Rupture: A Study From the Swedish National Anterior Cruciate Ligament Register.

PURPOSE: To analyze and compare clinical outcomes after anterior cruciate ligament (ACL) reconstruction 5 and 10 years postsurgery between patients with concomitant intra-articular injuries and those with isolated ACL injury at reconstruction. METHODS: Registrations were made using a web-based protocol by physicians for baseline and surgical data. Patients registered their Knee Injury and Osteoarthritis Outcome Score (KOOS) preoperatively and at 5 and 10 years postsurgery. The exclusion criteria for the present study were revisions of previously unregistered ACL surgeries, non-ACL surgeries, patients for whom 10-year follow-up data had not yet been collected, and the proportion of index surgeries that were revision or contralateral interventions. RESULTS: There were 1,295 KOOS scores available for patients 5 years postsurgery, and 1,023 10 years postsurgery from a baseline of 2,751 index reconstructions. A deterioration between the 5- and 10-year scores was observed for patients with concomitant meniscus injury on the KOOS subscales for pain (P = .015), symptoms (P = .005), sport and recreation (P = .011), and knee-related quality of life (QoL) (P = .03) compared with patients with isolated ACL injury. Correspondingly, KOOS subscale score deterioration was seen for combined concomitant cartilage and meniscus injuries for pain (P = .005), symptoms (P = .009), sport and recreation (P = .006), and QoL (P < .001). The largest deteriorations were found in sport and recreation (-5.9 points; confidence interval [CI] -10.1, -1.1) and QoL (-6.5 points; CI -10.3, -2.8) subscale scores for patients with concomitant meniscal and cartilage injuries. A similar pattern was not seen between patients with concomitant cartilage injury and isolated ACL injury. CONCLUSIONS: The present study reveals that concomitant meniscus injuries at the index operation, either in isolation or in combination with cartilage lesions, render a deterioration of scores on the KOOS outcome subscales for pain, sport and recreation, and quality of life between 5- and 10-year postsurgery follow-up of ACL-reconstructed patients. No such deterioration was seen for patients who had isolated ACL injury. LEVEL OF EVIDENCE: Level III, retrospective analysis of prospectively collected data.

Knee Arthroscopic Surgery in Middle-Aged Patients With Meniscal Symptoms: A 3-Year Follow-up of a Prospective, Randomized Study.

BACKGROUND: The optimal treatment for middle-aged patients with knee pain and meniscal lesions has been extensively debated. Most previous studies have revealed only short-term beneficial results of knee arthroscopic surgery. The authors have previously shown a positive benefit of knee arthroscopic surgery and an exercise program after 1 year when compared with an exercise program alone. PURPOSE: To evaluate if knee arthroscopic surgery combined with an exercise program provided an additional long-term benefit after 3 years compared with an exercise program alone in middle-aged patients with meniscal symptoms. STUDY DESIGN: Randomized controlled trial; Level of evidence, 1. METHODS: Of 179 eligible patients, aged 45 to 64 years, 150 were randomized to (1) a 3-month exercise program (nonsurgery group) or (2) the same as group 1 plus knee arthroscopic surgery within 4 weeks (surgery group). The primary outcome was the change in the Knee Injury and Osteoarthritis Outcome Score (KOOS) subscore of pain between baseline and the 3-year follow-up. Results from the 1-year follow-up have been published previously. RESULTS: Both treatment groups improved significantly in the KOOS pain subscore at 3 years' follow-up in the intention-to-treat and as-treated analyses ( P < .001). The between-group difference for the change in the KOOS pain subscore between baseline and the 3-year follow-up was no longer statistically significant, neither in the intention-to-treat analysis (7.6 points; 95% CI, -0.6 to 15.9; P = .068) nor in the as-treated analysis (5.3 points; 95% CI, -3.1 to 13.8; P = .216). The factorial analysis of the effect of the intervention and age, onset of pain, and mechanical symptoms indicated that older patients improved more, regardless of treatment, and surgery may be more beneficial for patients without mechanical symptoms (as-treated analysis). The effect of the predictive factors on the KOOS pain subscore was uncertain because of the small sample size in the subgroup analyses. CONCLUSION: The benefit of knee arthroscopic surgery, seen at 1 year in middle-aged patients with meniscal symptoms, was diminished at 3 years and was no longer statistically significant. CLINICAL RELEVANCE: Knee arthroscopic surgery may be beneficial for middle-aged patients with meniscal symptoms in addition to an exercise program. Older age and absence of mechanical symptoms should not be contraindications to surgery. Registration: NCT01288768 ( ClinicalTrials.gov identifier).

ACL injuries in men's professional football: a 15-year prospective study on time trends and return-to-play rates reveals only 65% of players still play at the top level 3†years after ACL rupture.

BACKGROUND: Studies investigating the development of ACL injuries over time in football are scarce and more data on what happens before and after return to play (RTP) are needed. AIM: To investigate (1) time trends in ACL injury rates, (2) complication rates before return to match play following ACL reconstruction, and (3) the influence of ACL injury on the subsequent playing career in male professional football players. METHODS: 78 clubs were followed between 2001 and 2015. Time trend in ACL injury rate was analysed using linear regression. ACL-injured players were monitored until RTP and tracked for 3 years after RTP. RESULTS: We recorded 157 ACL injuries, 140 total and 17 partial ruptures, with a non-significant average annual increase in the ACL injury rate by 6% (R(2)=0.13, b=0.059, 95% CI -0.04 to 0.15, p=0.20). The match ACL injury rate was 20-fold higher than the training injury rate (0.340 vs 0.017 per 1000 h). 138 players (98.6%) with a total rupture underwent ACL reconstruction; all 134 players with RTP data (4 players still under rehabilitation) were able to return to training, but 9 of them (6.7%) suffered complications before their first match appearance (5 reruptures and 4 other knee surgeries). The median layoff after ACL reconstruction was 6.6 months to training and 7.4 months to match play. We report 3-year follow-up data for 106 players in total; 91 players (85.8%) were still playing football and 60 of 93 players (65%) with ACL reconstruction for a total rupture played at the same level. CONCLUSIONS: The ACL injury rate has not declined during the 2000s and the rerupture rate before return to match play was 4%. The RTP rate within a year after ACL reconstruction was very high, but only two-thirds competed at the highest level 3 years later.

Predictors for additional anterior cruciate ligament reconstruction: data from the Swedish national ACL register.

PURPOSE: To identify predictors for additional anterior cruciate ligament (ACL) reconstruction. METHODS: Patients from the Swedish national ACL register who underwent ACL reconstruction between January 2005 and February 2013 (follow-up duration 6-104 months) were included. Cox regression analyses included the following independent variables regarding primary injury: age, sex, time between injury and primary ACL reconstruction, activity at primary injury, concomitant injuries, injury side, graft type, and pre-surgery KOOS and EQ-5D scores. RESULTS: Among ACL reconstruction procedures, 93% involved hamstring tendon (HT) autografts. Graft type did not predict additional ACL reconstruction. Final regression models only included patients with HT autograft (n = 20,824). Of these, 702 had revision and 591 contralateral ACL reconstructions. The 5-year post-operative rates of revision and contralateral ACL reconstruction were 4.3 and 3.8%, respectively. Significant predictors for additional ACL reconstruction were age (fourfold increased rate for <16-year-old patients vs. >35-year-old patients), time between injury and primary surgery (two to threefold increased rate for ACL reconstruction within 0-90 days vs. >365 days), and playing football at primary injury. CONCLUSION: This study identified younger age, having ACL reconstruction early after the primary injury, and incurring the primary injury while playing football as the main predictors for revision and contralateral ACL reconstruction. This suggests that the rate of additional ACL reconstruction is increased in a selected group of young patients aiming to return to strenuous sports after primary surgery and should be taken into consideration when discussing primary ACL reconstruction, return to sports, and during post-surgery rehabilitation. LEVEL OF EVIDENCE: II.

Fewer ligament injuries but no preventive effect on muscle injuries and severe injuries: an 11-year follow-up of the UEFA Champions League injury study.

BACKGROUND: Limited information is available on the variation in injury rates over multiple seasons of professional football. AIM: To analyse time-trends in injury characteristics of male professional football players over 11 consecutive seasons. METHODS: A total of 1743 players comprising 27 teams from 10 countries were followed prospectively between 2001 and 2012. Team medical staff recorded individual player exposure and time loss injuries. RESULTS: A total of 8029 time loss injuries were recorded. The match unavailability due to injury was 14% and constant over the study period. On average, a player sustained two injuries per season, resulting in approximately 50 injuries per team and season. The ligament injury rate decreased during the study period (R(2)=0.608, b=-0.040, 95% CI -0.065 to -0.016, p=0.005), whereas the rate of muscle injury (R(2)=0.228, b=-0.013, 95% CI -0.032 to 0.005, p=0.138) and severe injury (R(2)=0.141, b=0.015, 95% CI -0.013 to 0.043, p=0.255) did not change over the study period. In addition, no changes in injury rates over the 11-year period were found for either training (R(2)=0.000, b=0.000, 95% CI -0.035 to 0.034, p=0.988) or match play (R(2)=0.282, b=-0.015, 95% CI -0.032 to 0.003, p=0.093). CONCLUSIONS: The injury rate has decreased for ligament injuries over the last 11 years, but overall training, match injury rates and the rates of muscle injury and severe injury remain high.

Recurrence of Achilles tendon injuries in elite male football players is more common after early return to play: an 11-year follow-up of the UEFA Champions League injury study.

BACKGROUND: There is limited information about Achilles tendon disorders in professional football. AIMS: To investigate the incidence, injury circumstances, lay-off times and reinjury rates of Achilles tendon disorders in male professional football. METHODS: A total of 27 clubs from 10 countries and 1743 players have been followed prospectively during 11 seasons between 2001 and 2012. The team medical staff recorded individual player exposure and time-loss injuries. RESULTS: A total of 203 (2.5% of all injuries) Achilles tendon disorders were registered. A majority (96%) of the disorders were tendinopathies, and nine were partial or total ruptures. A higher injury rate was found during the preseason compared with the competitive season, 0.25 vs 0.18/1000 h (rate ratio (RR) 1.4, 95% CI 1.1 to 2.0; p=0.027). The mean lay-off time for Achilles tendinopathies was 23±37 (median=10, Q1=4 and Q3=24) days, while a rupture of the Achilles tendon, on average, caused 161±65 (median=169, Q1=110 and Q3=189) days of absence. Players with Achilles tendon disorders were significantly older than the rest of the cohort, with a mean age of 27.2±4 years vs 25.6±4.6 years (p<0.001). 27% of all Achilles tendinopathies were reinjuries. A higher reinjury risk was found after short recovery periods (31%) compared with longer recovery periods (13%) (RR 2.4, 95% CI 2.1 to 2.8; p<0.001). CONCLUSIONS: Achilles tendon disorders account for 3.8% of the total lay-off time and are more common in older players. Recurrence is common after Achilles tendinopathies and the reinjury risk is higher after short recovery periods.

Injuries affect team performance negatively in professional football: an 11-year follow-up of the UEFA Champions League injury study.

BACKGROUND: The influence of injuries on team performance in football has only been scarcely investigated. AIM: To study the association between injury rates and team performance in the domestic league play, and in European cups, in male professional football. METHODS: 24 football teams from nine European countries were followed prospectively for 11 seasons (2001-2012), including 155 team-seasons. Individual training and match exposure and time-loss injuries were registered. To analyse the effect of injury rates on performance, a Generalised Estimating Equation was used to fit a linear regression on team-level data. Each team's season injury rate and performance were evaluated using its own preceding season data for comparison in the analyses. RESULTS: 7792 injuries were reported during 1 026 104 exposure hours. The total injury incidence was 7.7 injuries/1000 h, injury burden 130 injury days lost/1000 h and player match availability 86%. Lower injury burden (p=0.011) and higher match availability (p=0.031) were associated with higher final league ranking. Similarly, lower injury incidence (p=0.035), lower injury burden (p<0.001) and higher match availability (p<0.001) were associated with increased points per league match. Finally, lower injury burden (p=0.043) and higher match availability (p=0.048) were associated with an increase in the Union of European Football Association (UEFA) Season Club Coefficient, reflecting success in the UEFA Champions League or Europa League. CONCLUSIONS: Injuries had a significant influence on performance in the league play and in European cups in male professional football. The findings stress the importance of injury prevention to increase a team's chances of success.

Return to play after thigh muscle injury in elite football players: implementation and validation of the Munich muscle injury classification.

BACKGROUND: Owing to the complexity and heterogeneity of muscle injuries, a generally accepted classification system is still lacking. AIMS: To prospectively implement and validate a novel muscle injury classification and to evaluate its predictive value for return to professional football. METHODS: The recently described Munich muscle injury classification was prospectively evaluated in 31 European professional male football teams during the 2011/2012 season. Thigh muscle injury types were recorded by team medical staff and correlated to individual player exposure and resultant time-loss. RESULTS: In total, 393 thigh muscle injuries occurred. The muscle classification system was well received with a 100% response rate. Two-thirds of thigh muscle injuries were classified as structural and were associated with longer lay-off times compared to functional muscle disorders (p<0.001). Significant differences were observed between structural injury subgroups (minor partial, moderate partial and complete injuries) with increasing lay-off time associated with more severe structural injury. Median lay-off time of functional disorders was 5-8 days without significant differences between subgroups. There was no significant difference in the absence time between anterior and posterior thigh injuries. CONCLUSIONS: The Munich muscle classification demonstrates a positive prognostic validity for return to play after thigh muscle injury in professional male football players. Structural injuries are associated with longer average lay-off times than functional muscle disorders. Subclassification of structural injuries correlates with return to play, while subgrouping of functional disorders shows less prognostic relevance. Functional disorders are often underestimated clinically and require further systematic study.

The UEFA injury study: 11-year data concerning 346 MCL injuries and time to return to play.

BACKGROUND: Medial collateral ligament (MCL) injury is the most common knee ligament injury in professional football. AIM: To investigate the rate and circumstances of MCL injuries and development over the past decade. METHODS: Prospective cohort study, in which 27 professional European teams were followed over 11 seasons (2001/2002 to 2011/2012). Team medical staffs recorded player exposure and time loss injuries. MCL injuries were classified into four severity categories. Injury rate was defined as the number of injuries per 1000 player-hours. RESULTS: 346 MCL injuries occurred during 1 057 201 h (rate 0.33/1000 h). The match injury rate was nine times higher than the training injury rate (1.31 vs 0.14/1000 h, rate ratio 9.3, 95% CI 7.5 to 11.6, p<0.001). There was a significant average annual decrease of approximately 7% (p=0.023). The average lay-off was 23 days, and there was no difference in median lay-off between index injuries and reinjuries (18 vs 13, p=0.20). Almost 70% of all MCL injuries were contact-related, and there was no difference in median lay-off between contact and non-contact injuries (16 vs 16, p=0.74). CONCLUSIONS: This largest series of MCL injuries in professional football suggests that the time loss from football for MCL injury is 23 days. Also, the MCL injury rate decreased significantly during the 11-year study period.

Upper extremity injuries in male elite football players.

PURPOSE: To investigate the epidemiology of upper extremity injuries in male elite football players and to describe their characteristics, incidence and lay-off times. METHODS: Between 2001 and 2011, 57 male European elite football teams (2,914 players and 6,215 player seasons) were followed prospectively. Time-loss injuries and exposure to training and matches were recorded on individual basis. RESULTS: In total, 11,750 injuries were recorded, 355 (3 %) of those affected the upper extremities giving an incidence of 0.23 injuries/1,000 h of football. The incidence in match play was almost 7 times higher than in training (0.83 vs. 0.12 injuries/1,000 h, rate ratio 6.7, 95 % confidence interval 5.5-8.3). As much as 32 % of traumatic match injuries occurred as a result of foul play situations. Goalkeepers had a significantly higher incidence of upper extremity injuries compared to outfield players (0.80 vs. 0.16 injuries/1,000 h, rate ratio 5.0, 95 % confidence interval 4.0-6.2). The average absence due to an upper extremity injury was 23 ± 34 days. CONCLUSIONS: Upper extremity injuries are uncommon among male elite football players. Goalkeepers, however, are prone to upper extremity injury, with a five times higher incidence compared to outfield players. LEVEL OF EVIDENCE: II.

Prevention of acute knee injuries in adolescent female football players: cluster randomised controlled trial.

OBJECTIVE: To evaluate the effectiveness of neuromuscular training in reducing the rate of acute knee injury in adolescent female football players. DESIGN: Stratified cluster randomised controlled trial with clubs as the unit of randomisation. SETTING: 230 Swedish football clubs (121 in the intervention group, 109 in the control group) were followed for one season (2009, seven months). PARTICIPANTS: 4564 players aged 12-17 years (2479 in the intervention group, 2085 in the control group) completed the study. INTERVENTION: 15 minute neuromuscular warm-up programme (targeting core stability, balance, and proper knee alignment) to be carried out twice a week throughout the season. MAIN OUTCOME MEASURES: The primary outcome was rate of anterior cruciate ligament injury; secondary outcomes were rates of severe knee injury (>4 weeks' absence) and any acute knee injury. RESULTS: Seven players (0.28%) in the intervention group, and 14 (0.67%) in the control group had an anterior cruciate ligament injury. By Cox regression analysis according to intention to treat, a 64% reduction in the rate of anterior cruciate ligament injury was seen in the intervention group (rate ratio 0.36, 95% confidence interval 0.15 to 0.85). The absolute rate difference was -0.07 (95% confidence interval -0.13 to 0.001) per 1000 playing hours in favour of the intervention group. No significant rate reductions were seen for secondary outcomes. CONCLUSIONS: A neuromuscular warm-up programme significantly reduced the rate of anterior cruciate ligament injury in adolescent female football players. However, the absolute rate difference did not reach statistical significance, possibly owing to the small number of events. TRIAL REGISTRATION: Clinical trials NCT00894595.

How does comorbidity influence healthcare costs? A population-based cross-sectional study of depression, back pain and osteoarthritis.

OBJECTIVES: To analyse how comorbidity among patients with back pain, depression and osteoarthritis influences healthcare costs per patient. A special focus was made on the distribution of costs for primary healthcare compared with specialist care, hospital care and drugs. DESIGN: Population-based cross-sectional study. SETTING: The County of Östergötland, Sweden. PATIENTS: Data on diagnoses and healthcare costs for all 266 354 individuals between 20 and 75 years of age, who were residents of the County of Östergötland, Sweden, in the year 2006, were extracted from the local healthcare register and the national register of drug prescriptions. MAIN OUTCOME MEASURES: The effects of comorbidity on healthcare costs were estimated as interactions in regression models that also included age, sex, number of other health conditions and education. RESULTS: The largest diagnosed group was back pain (11 178 patients) followed by depression (7412 patients) and osteoarthritis (5174 patients). The largest comorbidity subgroup was the combination of back pain and depression (772 patients), followed by the combination of back pain and osteoarthritis (527 patients) and the combination of depression and osteoarthritis (206 patients). For patients having both a depression diagnosis and a back pain diagnosis, there was a significant negative interaction effect on total healthcare costs. The average healthcare costs among patients with depression and back pain was SEK 11 806 lower for a patient with both diagnoses. In this comorbidity group, there were tendencies of a positive interaction for general practitioner visits and negative interactions for all other visits and hospital days. Small or no interactions at all were seen between depression diagnoses and osteoarthritis diagnoses. CONCLUSIONS: A small increase in primary healthcare visits in comorbid back pain and depression patients was accompanied with a substantial reduction in total healthcare costs and in hospital costs. Our results can be of value in analysing the cost effects of comorbidity and how the coordination of primary and secondary care may have an impact on healthcare costs.

Co-morbidity and health care utilisation five years prior to diagnosis for depression. A register-based study in a Swedish population.

BACKGROUND: Depressive disorders have been associated with a number of co-morbidities, and we hypothesized that patients with a depression diagnosis would be heavy users of health care services, not only when first evaluated for depression, but also for preceding years. The aim of this study was to investigate whether increased health care utilisation and co-morbidity could be seen during five years prior to an initial diagnosis of depression. METHODS: We used a longitudinal register-based study design. The setting comprised the general population in the county of Östergötland, south-east Sweden. All 2470 patients who were 20 years or older in 2006 and who received a new diagnosis of depression (F32 according to ICD-10) in 2006, were selected and followed back to the year 2001, five years before their depression diagnosis. A control group was randomly selected among those who were aged 20 years or over in 2006 and who had received no depression diagnosis during the period 2001-2006. RESULTS: Predictors of a depression diagnosis were a high number of physician visits, female gender, age below 60, age above 80 and a low socioeconomic status.Patients who received a diagnosis of depression used twice the amount of health care (e.g. physician visits and hospital days) during the five year period prior to diagnosis compared to the control group. A particularly strong increase in health care utilisation was seen the last year before diagnosis. These findings were supported with a high level of co-morbidity as for example musculoskeletal disorders during the whole five-year period for patients with a depression diagnosis. CONCLUSIONS: Predictors of a depression diagnosis were a high number of physician visits, female gender, age below 60, age above 80 and a low socioeconomic status. To find early signs of depression in the clinical setting and to use a preventive strategy to handle these patients is important.

Sun protection advice mediated by the general practitioner: an effective way to achieve long-term change of behaviour and attitudes related to sun exposure?

OBJECTIVE: To investigate, in primary health care, differentiated levels of prevention directed at skin cancer, and how the propensity of the patients to change sun habits/sun protection behaviour and attitudes towards sunbathing were affected, three years after intervention. Additionally, the impact of the performance of a phototest as a complementary tool for prevention was evaluated. DESIGN: Randomized controlled study. Setting and subjects. During three weeks in February, all patients ≥ 18 years of age registering at a primary health care centre in southern Sweden were asked to fill in a questionnaire mapping sun exposure habits, attitudes towards sunbathing, and readiness to increase sun protection according to the Transtheoretical Model of Behaviour Change (TTM) (n = 316). They were randomized into three intervention groups, for which sun protection advice was given, in Group 1 by means of a letter, and in Groups 2 and 3 orally during a personal GP consultation. Group 3 also underwent a phototest to demonstrate individual skin UV sensitivity. MAIN OUTCOME MEASURES: Change of sun habits/sun protection behaviour and attitudes, measured by five-point Likert scale scores and readiness to increase sun protection according to the TTM, three years after intervention, by a repeated questionnaire. RESULTS: In the letter group, almost no improvement in sun protection occurred. In the two doctor's consultation groups, significantly increased sun protection was demonstrated for several items, but the difference compared with the letter group was significant only for sunscreen use. The performance of a phototest did not appear to reinforce the impact of intervention. CONCLUSION: Sun protection advice, mediated personally by the GP during a doctor's consultation, can lead to improvement in sun protection over a prolonged time period.

Anterior cruciate ligament injury in elite football: a prospective three-cohort study.

Anterior cruciate ligament (ACL) injury causes long lay-off time and is often complicated with subsequent new knee injury and osteoarthritis. Female gender is associated with an increased ACL injury risk, but few studies have adjusted for gender-related differences in age although female players are often younger when sustaining their ACL injury. The objective of this three-cohort study was to describe ACL injury characteristics in teams from the Swedish men's and women's first leagues and from several European men's professional first leagues. Over a varying number of seasons from 2001 to 2009, 57 clubs (2,329 players) were followed prospectively and during this period 78 ACL injuries occurred (five partial). Mean age at ACL injury was lower in women compared to men (20.6 ± 2.2 vs. 25.2 ± 4.5 years, P = 0.0002). Using a Cox regression, the female-to-male hazard ratio (HR) was 2.6 (95% CI 1.4-4.6) in all three cohorts studied and 2.6 (95% CI 1.3-5.3) in the Swedish cohorts; adjusted for age, the HR was reduced to 2.4 (95% CI 1.3-4.2) and 2.1 (95% CI 1.0-4.2), respectively. Match play was associated with a higher ACL injury risk with a match-to-training ratio of 20.8 (95% CI 12.4-34.8) and 45 ACL injuries (58%) occurred due to non-contact mechanisms. Hamstrings grafts were used more often in Sweden than in Europe (67 vs. 34%, P = 0.028), and there were no differences in time to return to play after ACL reconstruction between the cohorts or different grafts. In conclusion, this study showed that the ACL injury incidence in female elite footballers was more than doubled compared to their male counterparts, but also that they were significantly younger at ACL injury than males. These findings suggest that future preventive research primarily should address the young female football player.