Anterior knee laxity is greater in athletic females who attain menarche at a younger age.

PURPOSE: Females with above-average anterior knee laxity values are at increased risk of anterior cruciate ligament (ACL) injury. The purpose of this study was to examine the effects of menarche age (MA) and menarche offset on anterior knee laxity in young, physically active women. METHODS: Anterior knee laxity (KT-2000) and menstrual characteristics (per self-report) were recorded in 686 Slovenian sportswomen from team handball, volleyball and basketball club sports (average years sport participation: 7.3 ± 3.6 years). Females were stratified into four groups based on their self-reported age at menarche: 9-11, 12, 13 and 14+ years. Anterior knee laxity was compared across MA groups using a univariate analysis of variance (ANOVA) with Bonferroni correction, with and without controlling for factors that could potentially differ between groups and influence anterior knee laxity. Females were then stratified into four groups based on the number of years they were away from their age at onset of menarche. Groups were compared using a univariate ANOVA with Bonferroni correction, with and without controlling for factors that differed between groups and could influence anterior knee laxity. RESULTS: Anterior knee laxity was greater in females who attained menarche at 12 years of age (6.4 ± 1.5 mm) or younger (6.6 ± 1.6 mm) compared to 14 years of age or older (5.8 ± 1.2 mm) (p < 0.001; partial η2 = 0.032). Anterior knee laxity was 0.7-1.4 mm greater in females who were 5 or more years away from menarche compared to those who were within 2 years of menarche (5.8 ± 1.3 mm; p < 0.001). CONCLUSION: Anterior knee laxity is greater in females who attained menarche at a younger age and in females who are 5 or more years postmenarche. Age of menarche represents a critical pubertal event that is easy for women to recall and may provide important insights into factors that moderate anterior knee laxity, a risk factor for ACL injury in women. LEVEL OF EVIDENCE: Level IV.

The Impact of Differential Knee Laxity on Brain Activation During Passive Knee Joint Loading.

Although higher anterior knee laxity is an established risk factor of ACL injury, underlying mechanisms are uncertain. While decreased proprioception and altered movement patterns in individuals with anterior knee laxity have been identified, the potential impact of higher laxity on brain activity is not well understood. Thus, the purpose of this study is to identify the impact of different magnitudes of knee laxity on brain function during anterior knee joint loading. Twenty-seven healthy and active female college students without any previous severe lower leg injuries volunteered for this study. Anterior knee laxity was measured using a knee arthrometer KT-2000 to assign participants to a higher laxity (N=15) or relatively lower laxity group (N=12). Functional magnetic resonance images were obtained during passive anterior knee joint loading in a task-based design using a 3T MRI scanner. Higher knee laxity individuals demonstrated diminished cortical activation in the left superior parietal lobe during passive anterior knee joint loading. Less brain activation in the regions associated with awareness of bodily movements in females with higher knee laxity may indicate a possible connection between brain activity and knee laxity. The results of this study may help researchers and clinicians develop effective rehabilitation programs for individuals with increased knee laxity. This article is protected by copyright. All rights reserved.

The Accuracy of Early Reproductive History and Physical Activity Participation Recall Across Multiple Age Ranges.

Background: The ability to accurately recall specific reproductive health events is an integral aspect of medical decision making and evaluating a female's overall health and wellness across their lifespan. The Health and Reproductive Survey (HeRS) was developed to recall reproductive events and environmental influences on reproductive characteristics throughout the lifespan of a female. This study aimed to determine how reliably women recall certain events during menarche and early reproductive years. It was hypothesized that age at menarche, hormonal contraceptive use, and physical activity would be recalled reliably among all age ranges, while the recall reliability for cycle regularity and length would be more inconsistent with advancing age. Materials and Methods: A total of 144 participants (age: 32.73 ± 11.92), completed the HeRS on two occasions spaced 4 months apart to investigate recall reliability. Cohen's kappa coefficient was used to assess the consistency of categorical responses and 95% limits of agreement were used for continuous data. Results: Although physical activity changes had greater variability than anticipated (0.79), the recall reliability among the youngest (1) and oldest (0.89) age groups was high, and females were able to consistently recall the age of menarche (0.83), physical activity level (0.9), cessation of period during early reproductive years (0.91), and birth control use following menarche (0.85) and during the early reproductive years (0.9). Conclusions: The HeRS is a useful tool for reliably recalling reproductive history and physical activity participation across multiple age ranges and can be utilized to gather crucial information throughout the reproductive lifespan.

Demographic Factors and Instantaneous Lower Extremity Injury Occurrence in a National Collegiate Athletic Association Division I Population.

CONTEXT: Temporal prediction of the lower extremity (LE) injury risk will benefit clinicians by allowing them to better leverage limited resources and target those athletes most at risk. OBJECTIVE: To characterize the instantaneous risk of LE injury by demographic factors of sex, sport, body mass index (BMI), and injury history. DESIGN: Descriptive epidemiologic study. SETTING: National Collegiate Athletic Association Division I athletic program. PATIENTS OR OTHER PARTICIPANTS: A total of 278 National Collegiate Athletic Association Division I varsity student-athletes (119 males, 159 females; age = 19.07 ± 1.21 years, height = 175.48 ± 11.06 cm, mass = 72.24 ± 12.87 kg). MAIN OUTCOME MEASURE(S): Injuries to the LE were tracked for 237 ± 235 consecutive days. Sex-stratified univariate Cox regression models were used to investigate the association between time to first LE injury and sport, BMI, and LE injury history. The instantaneous LE injury risk was defined as the injury risk at any given point in time after the baseline measurement. Relative risk ratios and Kaplan-Meier curves were generated. Variables identified in the univariate analysis were included in a multivariate Cox regression model. RESULTS: Female athletes displayed similar instantaneous LE injury risk to male athletes (hazard ratio [HR] = 1.29; 95% CI= 0.91, 1.83; P = .16). Overweight athletes (BMI >25 kg/m2) had similar instantaneous LE injury risk compared with athletes with a BMI of <25 kg/m2 (HR = 1.23; 95% CI = 0.84, 1.82; P = .29). Athletes with previous LE injuries were not more likely to sustain subsequent LE injury than athletes with no previous injury (HR = 1.09; 95% CI = 0.76, 1.54; P = .64). Basketball (HR = 3.12; 95% CI = 1.51, 6.44; P = .002) and soccer (HR = 2.78; 95% CI = 1.46, 5.31; P = .002) athletes had a higher risk of LE injury than cross-country athletes. In the multivariate model, instantaneous LE injury risk was greater in female than in male athletes (HR = 1.55; 95% CI = 1.00, 2.39; P = .05), and it was greater in male athletes with a BMI of >25 kg/m2 than that in all other athletes (HR = 0.44; 95% CI = 0.19, 1.00; P = .05), but these findings were not significantly different. CONCLUSIONS: In a collegiate athlete population, previous LE injury was not a contributor to the risk of future LE injury, whereas being female or being male with a BMI of >25 kg/m2 resulted in an increased risk of LE injury. Clinicians can use these data to extrapolate the LE injury risk occurrence to specific populations.

Sex-Specific Brain Activations during Single-Leg Exercise.

Background: Females have an increased incidence of musculoskeletal injuries compared to males. Sex differences in neuromuscular control has been widely studied regarding the dynamics and muscle activity during preplanned movements. While muscle activation patterns and movement biomechanics are understood to differ between sexes, it is not well understood how sex influences brain activity for lower extremity movement. Since the brain plays a vital role for voluntary movement and joint stability, it is important to understand the sex differences in brain function in order to better understand neuromuscular control associated with increased musculoskeletal injury risk in female. Hypothesis/Purpose: The purpose of this study is to understand the differences in brain activation patterns between sexes during a simple active knee extension-flexion movement. It was hypothesized that females would demonstrate higher cortical activation in the somatosensory areas compared to males as a compensatory strategy. Study Design: Cross-Sectional Study. Methods: Thirteen males and seventeen females who were healthy and physically active participated in this study (Male: 23.7±3.8 years, 74.5±13.5 kg, 172.3±6.4 cm; Female: 20.6±1.6 years, 65.4±12.8 kg, 163±6.1 cm). Functional magnetic resonance imaging data were obtained during a simple left knee extension-flexion exercise with their own leg weight while lying on the MRI table. The blood oxygen level dependent (BOLD) signals were compared between sexes. Results: There was significantly greater activation in the visual cortices and premotor cortex in females compared to males during the studied movement. Males demonstrated significantly greater activation in the right cerebellum. Conclusion: The results revealed sex differences in BOLD signal during simple knee extension-flexion movement. The results suggest that sex may be a biological factor in understanding brain activity associated with knee motor control. Level of Evidence: Level 3.

Examining the effects of femoral anteversion and passive hip rotation on ACL injury and knee biomechanics: a systematic review and meta-analysis.

PURPOSE: Greater femoral internal rotation (via anteversion or passive hip ROM) is associated with knee biomechanics thought to contribute to anterior cruciate ligament (ACL) injury, but it is unknown if femoral internal rotation contributes to actual ACL injury occurrence. The objective of this systematic review and meta-analysis was to quantify the extent to which femoral anteversion and hip range of motion (ROM) influence knee biomechanics consistent with ACL injury and actual ACL injury occurrence. METHODS: Using PRISMA guidelines, PubMed, CINAHL, SportDiscus, and Scopus databases were searched. Inclusion criteria were available passive hip ROM or femoral anteversion measure, ACL injury OR biomechanical analysis of functional task. Two reviewers independently reviewed titles, abstracts, and full texts when warranted. Included studies were submitted to Downs & Black Quality Assessment Tool. Meta-analyses were conducted for comparisons including at least two studies. RESULTS: Twenty-three studies were included (11 injury outcome, 12 biomechanical outcome). Decreased internal rotation ROM was significantly associated with history of ACL injury (MD -5.02°; 95% CI [-8.77°--1.27°]; p = 0.01; n = 10). There was no significant effect between passive external rotation and ACL injury (MD -2.62°; 95% CI [-5.66°-- 0.41°]; p = 0.09; n = 9) Participants displaying greater frontal plane knee projection angle had greater passive external rotation (MD 4.77°; 95% CI [1.17° - 8.37°]; p = 0.01; n = 3). There was no significant effect between femoral anteversion and ACL injury (MD -0.46°; 95% CI [-2.23°-1.31°]; p = 0.61; n = 2). No within-sex differences were observed between injured and uninjured males and females (p range = 0.09 - 0.63). CONCLUSION: Though individuals with injured ACLs have statistically less passive internal and external rotation, the observed heterogeneity precludes generalizability. There is no evidence that femoral anteversion influences biomechanics or ACL injury. Well-designed studies using reliable methods are needed to investigate biomechanical patterns associated with more extreme ROM values within each sex, and their prospective associations with ACL injury. LEVEL OF EVIDENCE: IV.

Ankle Dorsiflexion Affects Hip and Knee Biomechanics During Landing.

BACKGROUND: Restricted ankle dorsiflexion range of motion (DFROM) has been linked to lower extremity biomechanics that place an athlete at higher risk for injury. Whether reduced DFROM during dynamic movements is due to restrictions in joint motion or underutilization of available ankle DFROM motion is unclear. HYPOTHESIS: We hypothesized that both lesser total ankle DFROM and underutilization of available motion would lead to high-risk biomechanics (ie, greater knee abduction, reduced knee flexion). STUDY DESIGN: Cross-sectional study. LEVEL OF EVIDENCE: Level 3. METHODS: Nineteen active female athletes (age, 20.0 ± 1.3 years; height, 1.61 ± 0.06 m; mass, 67.0 ± 10.7 kg) participated. Maximal ankle DFROM (clinical measure of ankle DFROM [DF-CLIN]) was measured in a weightbearing position with the knee flexed. Lower extremity biomechanics were measured during a drop vertical jump with 3-dimensional motion and force plate analysis. The percent of available DFROM used during landing (DF-%USED) was calculated as the peak DFROM observed during landing divided by DF-CLIN. Univariate linear regressions were performed to identify whether DF-CLIN or DF-%USED predicted knee and hip biomechanics commonly associated with injury risk. RESULTS: For every 1.0° less of DF-CLIN, there was a 1.0° decrease in hip flexion excursion (r2 = 0.21, P = 0.05), 1.2° decrease in peak knee flexion angles (r2 = 0.37, P = 0.01), 0.9° decrease in knee flexion excursion (r2 = 0.40, P = 0.004), 0.002 N·m·N-1·cm-1 decrease in hip extensor work (r2 = 0.28, P = 0.02), and 0.001 N·m·N-1·cm-1 decrease in knee extensor work (r2 = 0.21, P = 0.05). For every 10% less of DF-%USED, there was a 3.2° increase in peak knee abduction angles (r2 = 0.26, P = 0.03) and 0.01 N·m·N-1·cm-1 lesser knee extensor work (r2 = 0.25, P = 0.03). CONCLUSION: Lower levels of both ankle DFROM and DF-%USED are associated with biomechanics that are considered to be associated with a higher risk of sustaining injury. CLINICAL RELEVANCE: While total ankle DFROM can predict some aberrant movement patterns, underutilization of available ankle DFROM can also lead to higher risk movement strategies. In addition to joint specific mobility training, clinicians should incorporate biomechanical interventions and technique feedback to promote the utilization of available motion.

Quadriceps muscle volume positively contributes to ACL volume.

Females have smaller anterior cruciate ligaments (ACLs) than males and smaller ACLs have been associated with a greater risk of ACL injury. Overall body dimensions do not adequately explain these sex differences. This study examined the extent to which quadriceps muscle volume (VOLQUAD ) positively predicts ACL volume (VOLACL ) once sex and other body dimensions were accounted for. Physically active males (N = 10) and females (N = 10) were measured for height, weight, and body mass index (BMI). Three-Tesla magnetic resonance images of their dominant and nondominant thigh and knee were then obtained to measure VOLACL , quadriceps, and hamstring muscle volumes, femoral notch width, and femoral notch width index. Separate three-step regressions estimated associations between VOLQUAD and VOLACL (third step), after controlling for sex (first step) and one body dimension (second step). When controlling for sex and sex plus BMI, VOLHAM , notch width, or notch width index, VOLQUAD consistently exhibited a positive association with VOLACL in the dominant leg, nondominant leg, and leg-averaged models (p < 0.05). Findings were inconsistent when controlling for sex and height (p = 0.038-0.102). Once VOLQUAD was included, only notch width and notch width index retained a statistically significant individual association with VOLACL (p < 0.01). Statement of Clinical Significance: The positive association between VOLQUAD and VOLACL suggests ACL size may in part be modifiable. Future studies are needed to determine the extent to which an appropriate training stimulus (focused on optimizing overall lower extremity muscle mass development) can positively impact ACL size and structure in young females.

Sex-Specific Changes in Physical Risk Factors for Anterior Cruciate Ligament Injury by Chronological Age and Stages of Growth and Maturation From 8 to 18 Years of Age.

OBJECTIVE: To critically assess the literature focused on sex-specific trajectories in physical characteristics associated with anterior cruciate ligament (ACL) injury risk by age and maturational stage. DATA SOURCES: PubMed, CINAHL, Scopus, and SPORTDiscus databases were searched through December 2021. STUDY SELECTION: Longitudinal and cross-sectional studies of healthy 8- to 18-year-olds, stratified by sex and age or maturation on ≥1 measure of body composition, lower extremity strength, ACL size, joint laxity, knee-joint geometry, lower extremity alignment, balance, or lower extremity biomechanics were included. DATA EXTRACTION: Extracted data included study design, participant characteristics, maturational metrics, and outcome measures. We used random-effects meta-analyses to examine sex differences in trajectory over time. For each variable, standardized differences in means between sexes were calculated. DATA SYNTHESIS: The search yielded 216 primary and 22 secondary articles. Less fat-free mass, leg strength, and power and greater general joint laxity were evident in girls by 8 to 10 years of age and Tanner stage I. Sex differences in body composition, strength, power, general joint laxity, and balance were more evident by 11 to 13 years of age and when transitioning from the prepubertal to pubertal stages. Sex differences in ACL size (smaller in girls), anterior knee laxity and tibiofemoral angle (greater in girls), and higher-risk biomechanics (in girls) were observed at later ages and when transitioning from the pubertal to postpubertal stages. Inconsistent study designs and data reporting limited the number of included studies. CONCLUSIONS: Critical gaps remain in our knowledge and highlight the need to improve our understanding of the relative timing and tempo of ACL risk factor development.

Effect of menstrual cycle phase, menstrual irregularities and hormonal contraceptive use on anterior knee laxity and non-contact anterior cruciate ligament injury occurrence in women: a protocol for a systematic review and meta-analysis.

Exercising women report three to six times more ACL tears than men, which happen, in the majority of cases, with a non-contact mechanism. This sex disparity has, in part, been attributed to the differences in reproductive hormone profiles between men and women. Many studies have shown that anterior knee (AK) laxity and the rate of non-contact ACL injuries vary across the menstrual cycle, but these data are inconsistent. Similarly, several studies have investigated the potential protective effect of hormonal contraceptives on non-contact ACL injuries, but their conclusions are also variable. The purpose of this systematic review and meta-analysis is to, identify, evaluate and summarise the effects of endogenous and exogenous ovarian hormones on AK laxity (primary outcome) and the occurrence of non-contact ACL injuries (secondary outcome) in women. We will perform a systematic search for all observational studies conducted on this topic. Studies will be retrieved by searching electronic databases, clinical trial registers, author's personal files and cross-referencing selected studies. Risk of bias will be assessed using the Newcastle Ottawa Quality Assessment Scale for Cohort and Case-Control Studies. Certainty in the cumulative evidence will be assessed using the Grading of Recommendations Assessment, Development and Evaluation approach. The meta-analyses will use a Bayesian approach to address specific research questions in a more intuitive and probabilistic manner. This review is registered on the international database of prospectively registered systematic reviews (PROSPERO; CRD42021252365).

Relationship of Anterior Cruciate Ligament Volume and T2* Relaxation Time to Anterior Knee Laxity.

BACKGROUND: High anterior knee laxity (AKL) has been prospectively identified as a risk factor for anterior cruciate ligament (ACL) injuries. Given that ACL morphometry and structural composition have the potential to influence ligamentous strength, understanding how these factors are associated with greater AKL is warranted. HYPOTHESIS: Smaller ACL volumes combined with longer T2* relaxation times would collectively predict greater AKL. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: College-aged active male (n = 20) and female (n = 30) participants underwent magnetic resonance imaging (MRI) and AKL testing. T2-weighted MRI scans were used to assess ACL volumes, and T2* relaxation times were used to assess ACL structural composition. AKL was measured via a commercial knee arthrometer. Forward stepwise linear regression with sex and weight (first step; suppressor variables) as well as ACL volume and T2* relaxation time (second step; independent variables) was used to predict AKL (dependent variable). RESULTS: After initially adjusting for sex and weight (R 2 = 0.19; P = .006), smaller ACL volumes combined with longer T2* relaxation times collectively predicted greater AKL (R 2 = 0.52; P < .001; R 2 Δ = 0.32; P Δ < .001). A smaller ACL volume was the primary predictor of greater AKL (R 2 Δ = 0.28; P < .001), with a longer T2* relaxation time trending toward a significant contribution to greater AKL (R 2 Δ = 0.04; P = .062). After adjusting for ACL volume and T2* relaxation time, sex (partial r = 0.05; P = .735) and weight (partial r = 0.05; P = .725) were no longer significant predictors. CONCLUSION: AKL was largely predicted by ACL volume and to a lesser extent by T2* relaxation time (and not a person's sex and weight). These findings enhance our understanding of how AKL may be associated with a structurally weaker ACL. The current study presents initial evidence that AKL is a cost-effective and clinically accessible measure that shows us something about the structural composition of the ACL. As AKL has been consistently shown to be a risk factor for ACL injuries, work should be done to continue to investigate what AKL may tell a clinician about the structure and composition of the ACL.

The Effects of Gluteal Strength and Activation on the Relationship Between Femoral Alignment and Functional Valgus Collapse During a Single-Leg Landing.

CONTEXT: A bias toward femoral internal rotation is a potential precursor to functional valgus collapse. The gluteal muscles may play a critical role in mitigating these effects. OBJECTIVE: Determine the extent to which gluteal strength and activation mediate associations between femoral alignment measures and functional valgus collapse. DESIGN: Cross-sectional. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: Forty-five females (age = 20.1 [1.7] y; height = 165.2 [7.6] cm; weight = 68.6 [13.1] kg) and 45 males (age = 20.8 [2.0] y; height = 177.5 [8.7] cm; weight = 82.7 [16.5] kg), healthy for 6 months prior. INTERVENTION(S): Femoral alignment was measured prone. Hip-extension and abduction strength were obtained using a handheld dynamometer. Three-dimensional biomechanics and surface electromyography were obtained during single-leg forward landings. MAIN OUTCOME MEASURES: Forward stepwise multiple linear regressions determined the influence of femoral alignment on functional valgus collapse and the mediating effects of gluteus maximus and medius strength and activation. RESULTS: In females, less hip abduction strength predicted greater peak hip adduction angle (R2 change = .10; P = .02), and greater hip-extensor activation predicted greater peak knee internal rotation angle (R2 change = .14; P = .01). In males, lesser hip abduction strength predicted smaller peak knee abduction moment (R2 change = .11; P = .03), and the combination of lesser hip abduction peak torque and lesser gluteus medius activation predicted greater hip internal rotation angle (R2 change = .15; P = .04). No meaningful mediation effects were observed (υadj < .01). CONCLUSIONS: In females, after accounting for femoral alignment, less gluteal strength and higher muscle activation were marginally associated with valgus movement. In males, less gluteal strength was associated with a more varus posture. Gluteal strength did not mediate femoral alignment. Future research should determine the capability of females to use their strength efficiently.

A Magnetic Resonance Imaging-Compatible Device to Perform In Vivo Anterior Knee Joint Loading.

CONTEXT: Greater anterior knee laxity (AKL) is associated with impaired sensory input and decreased functional knee stability. As functional magnetic resonance imaging (MRI) is the gold standard for understanding brain function, methods to load the anterior cruciate ligament in the MRI environment could further our understanding of the ligament's sensory role in knee joint stability. OBJECTIVE: To design and validate an MRI-compatible anterior knee joint loading device. DESIGN: Descriptive laboratory study. SETTING: University laboratory study. PARTICIPANTS: Sixteen healthy and physically active females participated (age = 23.4 [3.7] y; mass = 64.4 [8.4] kg). INTERVENTIONS: The AKL was assessed by a commercially available arthrometer. The AKL was also assessed with a custom-made, MRI-compatible device that produced anterior knee joint loading in a manner similar to the commercial arthrometer while obtaining dynamic structural MRI data. MAIN OUTCOME MEASUREMENTS: The AKL (in millimeters) at 133 N of loading was assessed with the commercial knee arthrometer. Anterior displacement of the tibia relative to the femur obtained at 133 N of loading was measured from dynamic MRI data obtained during usage of the custom device. Pearson correlations were used to examine relationships between the 2 measures. The 95% limits of agreement compared the absolute differences between the 2 devices. RESULTS: There was a 3.2-mm systematic difference between AKL (6.3 [1.6] mm) and anterior tibial translation (3.2 [1.0] mm) measures. There was a significant positive correlation between values obtained from the commercial arthrometer and the MRI-compatible device values (r = .553, P = .026). CONCLUSIONS: While systematic differences were observed, the MRI-compatible anterior knee joint loading device anteriorly translated the tibia relative to the femur in a similar manner to a commercial arthrometer design to stress the anterior cruciate ligament. Such a device may be beneficial in future functional magnetic resonance imaging study of anterior cruciate ligament mechanoreception.

Methods of Identifying Limb Dominance in Adolescent Female Basketball Players: Implications for Clinical and Biomechanical Research.

OBJECTIVE: To identify relationships between self-reported limb preferences and performance measures for determining limb dominance in adolescent female basketball players. DESIGN: Cross-sectional cohort study. PARTICIPANTS: Forty adolescent female basketball players. INDEPENDENT VARIABLES AND MAIN OUTCOME MEASURES: Participants provided self-reported preferred kicking and jumping limbs, then completed 3 trials of a single-limb countermovement hop (HOPVER) and unilateral triple hop for distance (HOPHOR) on each limb. Each test was used to independently define limb dominance by the limb that produced the largest maximum vertical height and horizontal distance, respectively. RESULTS: Chi-square tests for independence identified a significant relationship between self-reported preferred kicking and jumping legs (χ = 7.41, P = 0.006). However, no significant relationships were found when comparing self-reported preference to measures of performance during the HOPHOR (χ = 0.33, P = 0.57) or HOPVER (χ = 0.06, P = 0.80). In addition, the 2 performance measures did not consistently produce the same definition of limb dominance among individuals (χ = 1.52, P = 0.22). CONCLUSIONS: Self-selection of the dominant limb is unrelated to performance. Furthermore, limb dominance, as defined by vertical jump height, is unrelated to limb dominance defined by horizontal jump distance. The results of this study call into question the validity of consistently defining limb dominance by self-reported measures in adolescent female basketball players.

ACL Size and Notch Width Between ACLR and Healthy Individuals: A Pilot Study.

BACKGROUND: Given the relatively high risk of contralateral anterior cruciate ligament (ACL) injury in patients with ACL reconstruction (ACLR), there is a need to understand intrinsic risk factors that may contribute to contralateral injury. HYPOTHESIS: The ACLR group would have smaller ACL volume and a narrower femoral notch width than healthy individuals after accounting for relevant anthropometrics. STUDY DESIGN: Cross-sectional study. LEVEL OF EVIDENCE: Level 3. METHODS: Magnetic resonance imaging data of the left knee were obtained from uninjured (N = 11) and unilateral ACL-reconstructed (N = 10) active, female, collegiate-level recreational athletes. ACL volume was obtained from T2-weighted images. Femoral notch width and notch width index were measured from T1-weighted images. Independent-samples t tests examined differences in all measures between healthy and ACLR participants. RESULTS: The ACLR group had a smaller notch width index (0.22 ± 0.02 vs 0.25 ± 0.01; P = 0.004; effect size, 1.41) and ACL volume (25.6 ± 4.0 vs 32.6 ± 8.2 mm3/(kg·m)-1; P = 0.025; effect size, 1.08) after normalizing by body size. CONCLUSION: Only after normalizing for relevant anthropometrics, the contralateral ACLR limb had smaller ACL size and narrower relative femoral notch size than healthy individuals. These findings suggest that risk factor studies of ACL size and femoral notch size should account for relevant body size when determining their association with contralateral ACL injury. CLINICAL RELEVANCE: The present study shows that the method of the identified intrinsic risk factors for contralateral ACL injury could be used in future clinical screening settings.

Hip biomechanics differ in responders and non-responders to an ACL injury prevention program.

PURPOSE: To investigate the differences in demographic, anthropometric, biomechanical, and/or performance variables between those that do (responders) and do not (non-responders) exhibit reductions in knee abduction moments after an anterior cruciate ligament injury prevention program (ACL-IPP). METHODS: Forty-three adolescent female athletes completed biomechanical (3D motion analysis of a drop vertical jump) and performance testing before and after randomization into a 6-week ACL-IPP. Participants were classified into responders and non-responders based on their level of reduction of knee abduction moment from pre- to post-test. RESULTS: Compared to non-responders, responders exhibited increased hip adduction excursion at baseline (p = 0.02) and trended towards attending more training sessions (p = 0.07) and participating in soccer and not basketball (p = 0.07). Responders also showed greater improvements in hip flexion angles (p = 0.02) and moments (p < 0.001), and knee abduction angles (p < 0.001) and excursions (p = 0.001). There were no significant differences in age or experience with prior injury prevention programs (n.s.). CONCLUSIONS: After an ACL-IPP, athletes that exhibit the greatest reduction in knee abduction moments exhibit greater hip adduction excursion at baseline and show corresponding improvements in hip flexion and knee abduction kinematics and hip flexion moments. These results can help clinicians prospectively identify individuals that may not respond to an ACL-IPP and target individualized training for those at risk of injury. LEVEL OF EVIDENCE: I. CLINICAL TRIAL REGISTRATION NUMBER: Clinicaltrials.gov NCT02530333.

Temporal kinematic differences throughout single and double-leg forward landings.

Screening methods for anterior cruciate ligament (ACL) injuries often involve double-leg landings, though the majority of ACL injuries occur during single-leg landings. Differences in kinematic temporal characteristics between single-leg and double-leg landings are poorly understood. The purpose of this study was to examine discrete and temporal kinematics associated with functional valgus collapse during single-leg and double-leg landings (LANDSL and LANDDL). Three-dimensional kinematics were obtained during the landing phases of LANDSL and LANDDL in ninety participants (45 females: 20.1 ± 1.7 yr, 165.2 ± 7.6 cm, 68.6 ± 13.1 kg; 45 males: 20.7 ± 2.0 yr, 177.7 ± 8.5 cm, 82.8 ± 16.3 kg). Peak joint angles and time series curves for frontal and transverse plane hip and knee kinematics were analyzed with an RMANOVA (discrete variables) and Statistical Parametric Mapping (SPM) paired t-tests (time series). LANDSL elicited greater knee abduction than LANDDL from 0 to 35% (0-73 ms) but greater knee adduction from 54 to 100% (112-207 ms). Peak knee abduction was 2.0° greater during LANDDL than during LANDSL (p < .001). LANDSL elicited greater hip adduction than LANDDL from 2 to 33% (4-69 ms) and greater hip abduction from 49 to 100% (102-207 ms). Peak hip adduction was 4.6° greater during LANDSL than during LANDDL (p < .001). LANDSL elicited less knee internal rotation from 0 to 3% and greater hip internal rotation from 52 to 75% of the landing phase. Peak transverse plane joint angles did not differ between tasks. During the time frame in which ACL injuries are thought to occur, LANDSL elicited frontal plane knee and hip movement consistent with risky biomechanics. Researchers and clinicians should be cognizant of how a chosen screening task alters observed kinematic effects.