Endurance running during late murine adolescence results in a stronger anterior cruciate ligament and flatter posterior tibial slopes compared to controls

Abstract Background Anterior cruciate ligament (ACL) injury rates continue to rise among youth involved in recreational and competitive athletics, requiring a better understanding of how the knee structurally and mechanically responds to activity during musculoskeletal growth. Little is understood about how anatomical risk factors for ACL injury (e.g., small ACL size, narrow intercondylar notch, and steep posterior tibial slope) develop and respond to increased physical activity throughout growth. We hypothesized that the ACL-complex of mice engaged in moderate to strenuous physical activity (i.e., endurance running) throughout late adolescence and young adulthood would positively functionally adapt to repetitive load perturbations. Methods Female C57BL6/J mice (8 weeks of age) were either provided free access to a standard cage wheel with added resistance (n = 18) or normal cage activity (n = 18), for a duration of 4 weeks. Daily distance ran, weekly body and food weights, and pre- and post-study body composition measures were recorded. At study completion, muscle weights, three-dimensional knee morphology, ACL cross-sectional area, and ACL mechanical properties of runners and nonrunners were quantified. Statistical comparisons between runners and nonrunners were assessed using a two-way analysis of variance and a Tukey multiple comparisons test, with body weight included as a covariate. Results Runners had larger quadriceps (p = 0.02) and gastrocnemius (p = 0.05) muscles, but smaller hamstring (p = 0.05) muscles, compared to nonrunners. Though there was no significant difference in ACL size (p = 0.24), it was 13% stronger in runners (p = 0.03). Additionally, both the posterior medial and lateral tibial slopes were 1.2 to 2.2 degrees flatter than those of nonrunners (p < 0.01). Conclusions Positive functional adaptations of the knee joint to moderate to strenuous exercise in inbred mice offers hope that that some anatomical risk factors for ACL injury may be reduced through habitual physical activity. However, confirmation that a similar response to loading occurs in humans is needed.

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Assessing Physical Activity After ACL Injury: Moving Beyond Return to Sport

Sports Health A Multidisciplinary Approach ◽

10.1177/19417381211025307 ◽

2021 ◽

pp. 194173812110253

Author(s):

Christopher Kuenze ◽

Katherine Collins ◽

Karin Allor Pfeiffer ◽

Caroline Lisee

Keyword(s):

Physical Activity ◽

Anterior Cruciate Ligament ◽

Cruciate Ligament ◽

Young Patients ◽

Return To Sport ◽

Acl Injury ◽

Noncommunicable Diseases ◽

Successful Recovery ◽

Patient Reported ◽

Anterior Cruciate

Context: Return to sport is widely utilized by sports medicine researchers and clinicians as a primary outcome of interest for successful recovery when working with young patients who have undergone anterior cruciate ligament (ACL) reconstruction (ACLR). While return-to-sport outcomes are effective at tracking progress post-ACLR, they are limited because they do not necessarily capture physical activity (PA) engagement, which is important to maintain knee joint health and reduce the risk of noncommunicable diseases. Therefore, there is a critical need (1) to describe current PA participation and measurement recommendations; (2) to appraise common PA measurement approaches, including patient-reported outcomes and device-based methodologies; and (3) to provide clinical recommendations for future evaluation. Evidence Acquisition: Reports of patient-reported or device-based PA in patients with ACL injury were acquired and summarized based on a PubMed search (2000 through July 2020). Search terms included physical activity OR activity AND anterior cruciate ligament OR ACL. Study Design: Clinical review. Level of Evidence: Level 5. Results: We highlight that (1) individuals with ACLR are 2.36 times less likely to meet the US Department of Health and Human Services PA recommendations even when reporting successful return to sport, (2) common patient-reported PA assessments have significant limitations in the data that can be derived, and (3) alternative patient-reported and device-based assessments may provide improved assessment of PA in this patient population. Conclusion: Clinicians and researchers have relied on return to sport status or self-reported PA participation via surveys. These approaches are not consistent with current recommendations for PA assessment and do not allow for comparison with contemporary PA recommendations or guidelines. Return to sport, patient-reported outcome measures, and device-based assessment approaches should be used in complementary manners to comprehensively assess PA participation after ACLR. However, appropriate techniques should be used when assessing PA in adult and adolescent populations.

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Examining the Dynamic Nature of Anterior Cruciate Ligament Injury Risk Factors in Women’s Collegiate Soccer

Journal of Sport Rehabilitation ◽

10.1123/jsr.2021-0110 ◽

2021 ◽

pp. 1-8

Author(s):

Elena M. D’Argenio ◽

Timothy G. Eckard ◽

Barnett S. Frank ◽

William E. Prentice ◽

Darin A. Padua

Keyword(s):

Risk Factors ◽

Anterior Cruciate Ligament ◽

Range Of Motion ◽

Injury Risk ◽

External Rotation ◽

Cruciate Ligament ◽

Acl Injury ◽

Dynamic Risk Factors ◽

Dynamic Risk ◽

Anterior Cruciate

Context: Anterior cruciate ligament (ACL) injuries are a common and devastating injury in women’s soccer. Several risk factors for ACL injury have been identified, but have not yet been examined as potentially dynamic risk factors, which may change throughout a collegiate soccer season. Design: Prospective cohort study. Methods: Nine common clinical screening assessments for ACL injury risk, consisting of range of motion, movement quality, and power, were assessed in 29 Division I collegiate women’s soccer players. Preseason and midseason values were compared for significant differences. Change scores for each risk factor were also correlated with cumulative training loads during the first 10 weeks of a competitive soccer season. Results: Hip external rotation range of motion and power had statistically significant and meaningful differences at midseason compared with preseason, indicating they are dynamic risk factors. There were no significant associations between the observed risk factor changes and cumulative training load. Conclusions: Hip external rotation range of motion and power are dynamic risk factors for ACL injury in women’s collegiate soccer athletes. Serial screening of these risk factors may elucidate stronger associations with injury risk and improve prognostic accuracy of screening tools.

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Longitudinal Assessment of Noncontact Anterior Cruciate Ligament Injury Risk Factors During Maturation in a Female Athlete: A Case Report

Journal of Athletic Training ◽

10.4085/1062-6050-44.1.101 ◽

2009 ◽

Vol 44 (1) ◽

pp. 101-109 ◽

Cited By ~ 41

Author(s):

Gregory D. Myer ◽

Kevin R. Ford ◽

Jon G. Divine ◽

Eric J. Wall ◽

Leamor Kahanov ◽

...

Keyword(s):

Risk Factors ◽

Anterior Cruciate Ligament ◽

Body Mass ◽

Female Athlete ◽

Injury Risk ◽

Cruciate Ligament ◽

Acl Injury ◽

Knee Abduction ◽

Injury Risk Factors ◽

Anterior Cruciate

Abstract Objective: To present a unique case of a young pubertal female athlete who was prospectively monitored for previously identified anterior cruciate ligament (ACL) injury risk factors for 3 years before sustaining an ACL injury. Background: In prospective studies, previous investigators have examined cross-sectional measures of anatomic, hormonal, and biomechanical risk factors for ACL injury in young female athletes. In this report, we offer a longitudinal example of measured risk factors as the participant matured. Differential Diagnosis: Partial or complete tear of the ACL. Measurements: The participant was identified from a cohort monitored from 2002 until 2007. No injury prevention training or intervention was included during this time in the study cohort. Findings: The injury occurred in the year after the third assessment during the athlete's club basketball season. Knee examination, magnetic resonance imaging findings, and arthroscopic evaluation confirmed a complete ACL rupture. The athlete was early pubertal in year 1 of the study and pubertal during the next 2 years; menarche occurred at age 12 years. At the time of injury, she was 14.25 years old and postpubertal, with closing femoral and tibial physes. For each of the 3 years before injury, she demonstrated incremental increases in height, body mass index, and anterior knee laxity. She also displayed decreased hip abduction and knee flexor strength, concomitant with increased knee abduction loads, after each year of growth. Conclusions: During puberty, the participant increased body mass and height of the center of mass without matching increases in hip and knee strength. The lack of strength and neuromuscular adaptation to match the increased demands of her pubertal stature may underlie the increased knee abduction loads measured at each annual visit and may have predisposed her to increased risk of ACL injury.

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The Effect Of Playing Surface On Anterior Cruciate Ligament Injury In NCAA Soccer

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967120s00125 ◽

2020 ◽

Vol 8 (3_suppl2) ◽

pp. 2325967120S0012

Author(s):

Mark Howard ◽

Hyunwoo Paco Kang ◽

Samantha Solaru ◽

Alexander E. Weber ◽

Mark F. Rick C

Keyword(s):

Anterior Cruciate Ligament ◽

Cruciate Ligament ◽

Acl Injury ◽

Soccer Players ◽

Injury Incidence ◽

Artificial Turf ◽

Acl Injuries ◽

Natural Grass ◽

Significant Difference ◽

Anterior Cruciate

Objectives: Previous orthopaedic literature has examined the effect of synthetic playing surfaces on the risk of anterior cruciate ligament (ACL) injury in athletes and produced varying and inconclusive results. The objective of this study was to examine the role of playing surface on the incidence and risk of ACL injury in collegiate soccer athletes. Methods: The NCAA Injury Surveillance Program (ISP) database was queried for ACL injuries for male and female soccer players from the 2004-05 through the 2013-14 seasons at all levels of competition. The number of athlete exposures (AEs), defined as 1 athlete participating in 1 practice or competition in which they were exposed to the possibility of athletic injury, were recorded for grass and synthetic playing surfaces. Both the reported injuries and exposures provided were weighted in order to represent the entire NCAA collegiate soccer population. Normalized ACL incidence rates were calculated as well as 95% confidence intervals (95%CI). Rate ratios comparing competition type amongst both competition and practice were calculated. Results: ACL injuries were more common on grass surfaces (1.16 per 10,000 AEs, 95%CI 1.12-1.20) than artificial turf (0.92 per 10,000 AEs, 95%CI 0.84-1.04). This difference was statistically significant (IRR 1.26, p<0.0001), and driven primarily by the difference in injury incidence during practice. The injury incidence during practice on natural grass (1.18 per 10,000 AEs, 95% CI 1.11-1.26) was significantly greater than the injury incidence rate during practice on artificial turf (0.067 per 10,000 AEs, 95%CI 0.043-0.096). Players were 17.7 times more likely (95%CI 10.6678-27.2187, p<0.0001) to sustain an ACL injury during practice on natural grass when compared to practice on artificial turf. However, there was no significant difference in injury incidence during matches (IRR 0.96, p=0.44), with matches on natural grass (3.35 per 10,000 AEs, 95% CI 3.21-3.51) equivalent to matches on artificial surfaces (3.49 per 10,000 AEs, 95%CI 3.18-3.81). When comparing exposure type, the injury rate was significantly greater during matches (3.38 per 10,000 AEs, 95% CI 3.25-3.52) compared to practices (0.82 per 10,000 AEs, 95%CI 0.77-0.88), with a 4.10-fold increase in ACL injury incidence during matches compared to practice (p<0.0001). Conclusion: Between 2004 and 2014, NCAA soccer players experienced a greater number of ACL injuries on natural grass playing surfaces compared with artificial turf playing surfaces. This difference is driven by injuries during practice, where athletes were nearly 18 times more likely to suffer an ACL injury on grass versus artificial turf. While ACL injuries were more likely during matches compared to practices, no difference in incidence was noted between playing surfaces. Additional study is warranted investigating potential causes for this observed increased risk with soccer practice on grass fields.

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Anterior Cruciate Ligament Injury

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967114s00250 ◽

2014 ◽

Vol 2 (12_suppl4) ◽

pp. 2325967114S0025

Author(s):

Tomas Vilaseca ◽

Jorge Chahla ◽

Gustavo Gomez Rodriguez ◽

Damián Arroquy ◽

Gonzalo Perez Herrera ◽

...

Keyword(s):

Anterior Cruciate Ligament ◽

Internal Rotation ◽

Cruciate Ligament ◽

Acl Injury ◽

T Test ◽

Control Group ◽

Recreational Athletes ◽

Significant Difference ◽

Anterior Cruciate ◽

Knee Pathology

Objectives: The objective of this study was to analyze whether it is more frequent the presence of a decreased range of motion in the hips of recreational athletes with primary injury of the anterior cruciate ligament (ACL) than in a control group of volunteers without knee pathology. Methods: We included prospectively recreational athletes between 18 and 40 years with an acute ACL injury between January 2011 and January 2013. They were compared with a control group of volunteers recreational athletes without lower limb pathology and in the same range of age. The internal and external rotations passively prior to the point at which the pelvis movement contributes were observed. The results were statistically analyzed using t test for related samples to the hips of patients with ACL injury and t test for independent variables for comparison with the control group. Results: 48 patients with ACL injury and 53 healthy volunteers were evaluated. The ACL group was composed of 32 males and 16 females with an average age of 29.3 years. In the control group 26 males and 27 females were studied with a mean age of 26.6 years. Internal (IR) and external (ER) rotation in the LCA group was 22,9º and 55,5º respectively in the ipsilateral hip and 27,9º and 57,7º in the contralateral. In the control group a 35,9º of IR and 55,2º of ER was observed. The analysis showed an association between ACL injury and hypomotility of the hip further expense of a decrease in internal rotation. The analysis showed an association between ACL injury and hypomotility of the hip at the expense to a greater decrease in internal rotation. Conclusion: We found a statistically significant difference in the mobility of the hips in patients with ACL injury predominantly due to internal rotation, pattern that allows us to interpret this injury not only as an intrinsic etiology of the knee but also of the adjacent joints. We consider very importance to incorporate prevention activities and screening of risk factors regarding to at least high performance athletes.

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Protracted Cardiovascular Impairments After Anterior Cruciate Ligament Injury: A Critically Appraised Topic

Journal of Sport Rehabilitation ◽

10.1123/jsr.2019-0175 ◽

2020 ◽

Vol 29 (5) ◽

pp. 680-683

Author(s):

Cody R. Butler ◽

Kirsten Allen ◽

Lindsay J. DiStefano ◽

Lindsey K. Lepley

Keyword(s):

Physical Activity ◽

Anterior Cruciate Ligament ◽

National Football League ◽

Cruciate Ligament ◽

Acl Injury ◽

Cross Sectional ◽

History Of ◽

Cross Sectional Studies ◽

Anterior Cruciate ◽

Cv Disease

Clinical Scenario: Anterior cruciate ligament (ACL) tear is a devastating knee injury with negative long-term consequences, such as early-onset knee osteoarthritis, biomechanical compensations, and reduced physical activity. Significant reduction in physical activity is a powerful indicator of cardiovascular (CV) disease; therefore, those with a history of ACL injury may be at increased risk for CV disease compared with noninjured individuals. Focused Clinical Question: Do individuals with a history of ACL injury demonstrate negative CV changes compared with those without a history of ACL injury? Summary of Key Findings: Three articles met the inclusion criteria and investigated CV changes after ACL injury. Both cross-sectional studies compared participants with ACL injury with matched controls. Bell et al compared time spent in moderate to vigorous physical activity and step count, whereas Almeida et al compared maximum rate of oxygen consumption, ventilatory thresholds, isokinetic quadriceps strength, and body composition. Collectively, both quantitative studies found that individuals with a history of ACL injury had less efficient CV systems compared with matched controls and/or preoperative data. Finally, a qualitative study of 3506 retired National Football League athletes showed an increased rate of arthritis and knee replacement surgery after an ACL injury when compared with other retired National Football League members, in addition to a >50% increased rate of myocardial infarction. Clinical Bottom Line: A history of ACL injury is a source of impaired physical activity. Preliminary data indicate that these physical activity limitations negatively impair the CV system, and individuals with a history of ACL injury demonstrate lower maximum oxygen consumption, self-reported disability, and daily step count compared with noninjured peers. These complications support the need for greater emphasis on CV wellness. Strength of Recommendation: Consistent findings from 2 cross-sectional studies and 1 survey study suggest level IIB evidence to support that ACL injury is associated with negative CV health.

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Tendency of Driving to the Basket Is Associated With Increased Risk of Anterior Cruciate Ligament Tears in National Basketball Association Players: A Cohort Study

Orthopaedic Journal of Sports Medicine ◽

10.1177/23259671211052953 ◽

2021 ◽

Vol 9 (11) ◽

pp. 232596712110529

Author(s):

Blake J. Schultz ◽

Kevin A. Thomas ◽

Mark Cinque ◽

Joshua D. Harris ◽

William J. Maloney ◽

...

Keyword(s):

Anterior Cruciate Ligament ◽

Standard Deviation ◽

Cruciate Ligament ◽

Acl Injury ◽

National Basketball Association ◽

Acl Injuries ◽

Increased Risk ◽

Significant Difference ◽

Anterior Cruciate ◽

Level Performance

Background: Driving to the basket in basketball involves acceleration, deceleration, and lateral movements, which may expose players to increased anterior cruciate ligament (ACL) injury risk. It is unknown whether players who heavily rely on driving have decreased performance on returning to play after ACL reconstruction (ACLR). Hypothesis: Players with a greater tendency to drive to the basket would be more likely to tear their ACL versus noninjured controls and would experience decreased performance when returning to play after ACLR. Study Design: Case-control study; Level of evidence, 3. Methods: Season-level performance statistics and ACL injuries were aggregated for National Basketball Association (NBA) seasons between 1980 and 2017 from publicly available sources. Players’ tendency to drive was calculated using 49 common season-level performance metrics. Each ACL-injured player was matched with 2 noninjured control players by age, league experience, and style of play metrics. Points, playing minutes, driving, and 3-point shooting tendencies were compared between players with ACL injuries and matched controls. Independent-samples t test was utilized for comparisons. Results: Of 86 players with a total of 96 ACL tears identified in the NBA, 50 players were included in the final analysis. Players who experienced an ACL tear had a higher career-average drive tendency than controls ( P = .047). Players with career-average drive tendency ≥1 standard deviation above the mean were more likely to tear their ACL than players with drive tendency <1 standard deviation (5.2% vs 2.7%; P = .026). There was no significant difference in total postinjury career points ( P = .164) or career minutes ( P = .237) between cases and controls. There was also no significant change in drive tendency ( P = .152) or 3-point shooting tendency ( P = .508) after return to sport compared with controls. Conclusion: NBA players with increased drive tendency were more likely to tear their ACL. However, players who were able to return after ACLR did not underperform compared with controls and did not alter their style of play compared with the normal changes seen with age. This information can be used to target players with certain playing styles for ACL injury prevention programs.

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Increased Lateral Femoral Condyle Ratio Measured by MRI Is Associated with Higher Risk of Noncontact Anterior Cruciate Ligament Injury

10.21203/rs.3.rs-1087807/v1 ◽

2021 ◽

Author(s):

Miao He ◽

Jie Li

Keyword(s):

Risk Factors ◽

Logistic Regression ◽

Anterior Cruciate Ligament ◽

Diagnostic Performance ◽

Femoral Condyle ◽

Cruciate Ligament ◽

Acl Injury ◽

Tibial Slope ◽

Lateral Femoral Condyle ◽

Anterior Cruciate

Abstract Background Studies have shown a significant association between the radiographically measured lateral femoral condyle ratio (LFCR) and anterior cruciate ligament (ACL) injury. However, it is unclear whether the the LFCR measured by magnetic resonance imaging (MRI) is associated with risk of noncontact ACL injury. Objective 1 To investigate the effect of the LFCR on the risk of noncontact ACL injury by MRI. 2 To investigate the association of the LFCR measured by MRI with multiple bone morphological risk factors and evaluate the most sensitive risk predictors of noncontact ACL injury. Methods A total of 116 patients, including 58 subjects with noncontact ACL injury and 58 age-matched and sex-matched controls with only meniscus injury, were included in this retrospective case-control study. The LFCR, lateral tibial slope (LTS), lateral tibial height (LTH), medial tibial slope (MTS), and medial tibial depth (MTD) were measured on MRI. The differences in each index between the two groups were compared, and risk factors were screened by single-factor logistic regression analysis. Indicators with P values <0.1 were included in the logistic regression equation. The critical values and areas under the curve (AUCs) of independent risk factors were determined by receiver operating characteristic (ROC) curve analysis. Finally, the diagnostic performance of each risk factor was evaluated by the Z-test. Results A total of 116 patients who met the inclusion criteria were included in the final analysis (58 cases in the noncontact ACL injury group and 58 cases in the control group). Patients with noncontact ACL injury had a higher femoral LFCR (63.5±2.7%) than patients with simple meniscus tear. Among all the risk factors for ACL injury, the AUC for the LFCR was the largest, at 0.81 (95% CI, 0.73-0.88), and when the critical value was 61.35%, the sensitivity and specificity for the diagnosis of ACL injury were 79% and 67%, respectively. Combined with the LTH (> 2.35 mm), the diagnostic performance was improved. The AUC was 0.85 (95% CI, 0.78-0.92), the sensitivity was 0.83, and the specificity was 0.76 Conclusion This study shows that an increased LFCR is related to an increased risk of noncontact ACL injury by MRI. The LFCR and LTH are the most sensitive risk factors for noncontact ACL injury and may help clinicians identify individuals prone to ACL injury, allowing prevention and intervention measures to be applied.

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Higher risk of ACL rupture in amateur football compared to professional football: 5-year results of the ‘Anterior cruciate ligament-registry in German football’

Knee Surgery Sports Traumatology Arthroscopy ◽

10.1007/s00167-021-06737-y ◽

2021 ◽

Author(s):

Dominik Szymski ◽

Leonard Achenbach ◽

Johannes Zellner ◽

Johannes Weber ◽

Matthias Koch ◽

...

Keyword(s):

Risk Factors ◽

Anterior Cruciate Ligament ◽

Cruciate Ligament ◽

Acl Injury ◽

Media Analysis ◽

Skill Level ◽

Targeted Prevention ◽

Professional Football ◽

Acl Injuries ◽

Anterior Cruciate

Abstract Purpose Anterior cruciate ligament (ACL) injuries are a common severe type of football injury at all levels of play. A football-specific ACL registry providing both prospective ACL injury data according to the skill level and risk factors for ACL injury is lacking in the literature. Methods This study is based on the prospective ‘ACL registry in German Football’ implemented in the 2014–15 season. Professional (1st–3rd league), semi-professional (4th–6th league) and amateur leagues (7th league) were analysed regarding the incidence and risk factors for ACL injuries. Injuries were registered according to the direct reports of the injured players to the study office and double-checked via media analysis. After injury registration, the players received a standardised questionnaire. Data were analysed from the 2014–15 to the 2018–19 football season. Results Overall, 958 ACL injuries were registered during the 5-year study period. The incidence of ACL injuries was highest in amateur football (0.074/1000 h football exposure) compared to professional (0.058/1000 h; p < 0.0001) and semi-professional football (0.043/1000 h; p < 0.0001). At all skill levels, match incidence (professional: 0.343; semi-professional: 0.249; amateur: 0.319) was significantly higher than training incidence (professional: 0.015; semi-professional: 0.004; amateur: 0.005). Major risk factors were previous ACL injury (mean: 23.3%), other knee injuries (mean: 19.3%) and move to a higher league (mean: 24.2%). Conclusion This sports-specific ACL registry provides detailed information on the incidence and risk factors for ACL injuries in football over five years. Risk factors are skill level, match exposure, move to a higher league and previous knee injury. These factors offer potential starting points for screening at-risk players and applying targeted prevention. Level of evidence II.

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Risk Factors for Anterior Cruciate Ligament Injury in Competitive Adolescent Alpine Skiers

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967118766830 ◽

2018 ◽

Vol 6 (4) ◽

pp. 232596711876683 ◽

Cited By ~ 6

Author(s):

Maria Westin ◽

Marita L. Harringe ◽

Björn Engström ◽

Marie Alricsson ◽

Suzanne Werner

Keyword(s):

Risk Factors ◽

Anterior Cruciate Ligament ◽

Cruciate Ligament ◽

Acl Injury ◽

Left Knee ◽

Alpine Skiing ◽

Acl Injuries ◽

Alpine Skiers ◽

Anterior Cruciate ◽

Reduced Risk

Background: There is a high risk for anterior cruciate ligament (ACL) injuries in alpine skiers. To reduce or try to prevent these injuries, intrinsic and extrinsic risk factors need to be identified. Purpose: To identify possible intrinsic and extrinsic ACL injury risk factors among competitive adolescent alpine skiers. Study Design: Case-control study; Level of evidence, 3. Methods: Between 2006 and 2009, a cohort of 339 alpine ski students (176 male, 163 female) from Swedish ski high schools were prospectively observed in terms of ACL injuries. First-time ACL injuries were recorded. In September, prior to each ski season, the skiers were clinically examined according to a specific knee protocol. Results: Overall, 11 male and 14 female skiers sustained a total of 25 first-episode ACL injuries. The majority of injuries occurred in the left knee ( P < .05). Skiers who had participated in alpine skiing for >13 years (hazard ratio, 0.83; 95% CI, 0.68-1.00; P < .05) had a reduced risk of sustaining an ACL injury. Eighteen ACL injuries occurred during training, 12 in the technical discipline of giant slalom, and 8 in slalom. Fourteen skiers reported not to be fatigued at all at the time of injury, and 8 skiers reported that they were somewhat fatigued. Conclusion: ACL injuries occurred more often in the left knee than the right. This should be taken into consideration in the design of ACL injury prevention programs. Those who reported a higher number of active years in alpine skiing showed a reduced risk of sustaining an ACL injury. No other factor among those studied could be identified as an independent risk factor for ACL injury.

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