The effects of single-leg landing technique on ACL loading

Effects of attentional focus strategies in drop landing biomechanics of individuals with unilateral functional ankle instability

Background

Functional Ankle Instability (FAI) is a pervasive condition that can emerge following inadequate management of lateral ankle sprains. It is hallmarked by chronic joint instability and a subsequent deterioration in physical performance. The modulation of motor patterns through attentional focus is a well-established concept in the realm of motor learning and performance optimization. However, the precise manner in which attentional focus can rehabilitate or refine movement patterns in individuals with FAI remains to be fully elucidated.

Objective

The primary aim of this study was to evaluate the impact of attentional focus strategies on the biomechanics of single-leg drop landing movements among individuals with FAI.

Methods

Eighteen males with unilateral FAI were recruited. Kinematic and kinetic data were collected using an infrared three-dimensional motion capture system and force plates. Participants performed single-leg drop landing tasks under no focus (baseline), internal focus (IF), and external focus (EF) conditions. Biomechanical characteristics, including joint angles, ground reaction forces, and leg stiffness, were assessed. A 2 × 3 [side (unstable and stable) × focus (baseline, IF, and EF)] Repeated Measures Analysis of Variance (RM-ANOVA) analyzed the effects of attentional focus on biomechanical variables in individuals with FAI.

Results

No significant interaction effects were observed in this study. At peak vertical ground reaction force (vGRF), the knee flexion angle was significantly influenced by attentional focus, with a markedly greater angle under EF compared to IF (p < 0.001). Additionally, at peak vGRF, the ankle joint plantarflexion angle was significantly smaller with EF than with IF (p < 0.001). Significant main effects of focus were found for peak vGRF and the time to reach peak vGRF, with higher peak vGRF values observed under baseline and IF conditions compared to EF (p < 0.001). Participants reached peak vGRF more quickly under IF (p < 0.001). Leg Stiffness (kleg) was significantly higher under IF compared to EF (p = 0.001).

Conclusion

IF enhances joint stability in FAI, whereas EF promotes a conservative landing strategy with increased knee flexion, dispersing impact and minimizing joint stress. Integrating these strategies into FAI rehabilitation programs can optimize lower limb biomechanics and reduce the risk of reinjury.

Effect of fatigue on knee biomechanics during the sidestep cutting manoeuvre: A modelling approach

Loading both lateral and medial compartments is crucial to understanding the effect of muscle fatigue during sidestep cutting. The present study investigated the changes in tibiofemoral contact forces in the medial and lateral compartments and the muscle force contributions during the sidestep-cutting manoeuvre after a handball-specific fatigue protocol. Twenty female handball athletes performed three trials of the sidestep-cutting manoeuvre before (baseline) and after the fatigue protocol. Motion capture and ground reaction forces were measured, and the data were processed in OpenSim. The variables were compared using statistical parametric mapping (SPM), with a significance level of p < 0.05. The results showed a decreased knee flexion angle during fatigue in the early stance phase. In addition, the post-fatigue analysis demonstrated significantly reduced forces in vasti muscles. Similarly, during fatigue, the SPM analysis showed decreased tibiofemoral contact forces in the vertical and anterior directions. Vertical force applied to both medial and lateral condyles demonstrated a significant reduction after the fatigue protocol. These results indicated that forces applied to the tibiofemoral joint were reduced following the fatigue protocol compared to the baseline values. However, no consistent evidence exists that fatigue increases the risk of knee injuries.

Computational study of extrinsic factors affecting ACL strain during single-leg jump landing

BACKGROUND

Non-contact anterior cruciate ligament (ACL) injuries are a major concern in sport-related activities due to dynamic knee movements. There is a paucity of finite element (FE) studies that have accurately replicated the knee geometry, kinematics, and muscle forces during dynamic activities. The objective of this study was to develop and validate a knee FE model and use it to quantify the relationships between sagittal plane knee kinematics, kinetics and the resulting ACL strain.

METHODS

3D images of a cadaver knee specimen were segmented (bones, cartilage, and meniscus) and meshed to develop the FE model. Knee ligament insertion sites were defined in the FE model via experimental digitization of the specimen's ligaments. The response of the model was validated against multiple physiological knee movements using published experimental data. Single-leg jump landing motions were then simulated on the validated model with muscle forces and kinematic inputs derived from motion capture and rigid body modelling of ten participants.

RESULTS

The maximum ACL strain measured with the model during jump landing was 3.5 ± 2.2%, comparable to published experimental results. Bivariate analysis showed no significant correlation between body weight, ground reaction force and sagittal plane parameters (such as joint flexion angles, joint moments, muscle forces, and joint velocity) and ACL strain. Multivariate regression analysis showed increasing trunk, hip and ankle flexion angles decreases ACL strain (R2 = 90.04%, p < 0.05).

CONCLUSIONS

Soft landing decreases ACL strain and the relationship could be presented through an empirical equation. The model and the empirical relation developed in this study could be used to better predict ACL injury risk and prevention strategies during dynamic activities.

Injury Prevention Programmes Fail to Change Most Lower Limb Kinematics and Kinetics in Female Team Field and Court Sports: A Systematic Review and Meta-Analysis of Randomised Controlled Trials

BACKGROUND

One mechanism by which exercise interventions may be effective in reducing anterior cruciate ligament (ACL) injury risk is through changes in lower limb biomechanics. Understanding how training programmes affect lower-limb kinematics and kinetics may help refine injury prevention programmes.

OBJECTIVE

The aim of this systematic review and meta-analysis was to assess the effect of injury prevention programmes on kinematics and kinetics during tasks related to ACL injury in female team field and court sports.

DATA SOURCES

Five databases were searched in October 2022.

ELIGIBILITY CRITERIA

Randomised controlled trials assessing the effect of injury prevention programmes compared with usual training/no training on lower limb kinematics and kinetics in female team field and court sports were eligible for review.

RESULTS

Sixteen studies were included. A total of 976 female athletes were included. Most of the studies included interventions with multiple components (12/16). Commonly used components were plyometrics (12/16), strength (8/16), and balance/stability (7/16). Thirteen studies had routine training or sham interventions as the control group and three studies had no training. Very low certainty evidence suggests that injury prevention programmes increase knee flexion angles (mean difference = 3.1° [95% confidence interval 0.8-5.5]); however, very low to low certainty evidence suggests no effect on hip flexion angles/moments, knee flexion moments, hip adduction angles/moments, knee adduction angles/moments, hip internal rotation angles/moments, ankle dorsiflexion angles, and ground reaction forces, compared with usual training/no training.

CONCLUSION

Injury prevention programmes may be effective in increasing knee flexion angles during dynamic landing and cutting tasks but may have no effect on other lower limb biomechanical variables. As such, the benefits of injury prevention programmes may be mediated by factors other than altered biomechanics and/or may happen through other biomechanical measures not included in this review.

Biomechanical behavior of the lower limbs and of the joints when landing from different heights

Landing from a jump is a challenging task as the energy accumulated during the aerial phase of the jump must be fully dissipated by the lower limbs during landing; the higher the jump height, the greater the amount of energy to be dissipated. In the present study, we aim to understand (1) how the biomechanical behavior is tuned as a function of the mechanical demand, and (2) the relationship between the self-selected landing strategy and the behavior of the joints. Fourteen subjects were asked to drop off a box of 10 to 60 cm height and land on the ground. The ground reaction forces and the kinematics were recorded using force plates and a motion capture system. A model was used to estimate the properties, i.e. stiffness and damping, of the lower limbs and of the joints. Our results show that, whatever the amount of energy to be dissipated (i.e. height of the jump), the lower limbs and the anke and knee joints behave first as a spring, then as a spring-damper system. However each joint plays a specific role: during the spring phase, the behaviour of the lower limb is associated with the stiffness of the ankle and with the landing constraints (i.e. force peak and loading rate), while during the spring-damper phase, it is associated with the stiffness of the knee and with the amount of energy to be dissipated. Our findings suggest that constraints and performance result from a distinct control of biomechanical parameters at the joints.

Patellar Tendon Load Progression during Rehabilitation Exercises: Implications for the Treatment of Patellar Tendon Injuries

PURPOSE

This study aimed to evaluate patellar tendon loading profiles (loading index, based on loading peak, loading impulse, and loading rate) of rehabilitation exercises to develop clinical guidelines to incrementally increase the rate and magnitude of patellar tendon loading during rehabilitation.

METHODS

Twenty healthy adults (10 females/10 males, 25.9 ± 5.7 yr) performed 35 rehabilitation exercises, including different variations of squats, lunge, jumps, hops, landings, running, and sports specific tasks. Kinematic and kinetic data were collected, and a patellar tendon loading index was determined for each exercise using a weighted sum of loading peak, loading rate, and cumulative loading impulse. Then the exercises were ranked, according to the loading index, into tier 1 (loading index ≤0.33), tier 2 (0.33 < loading index <0.66), and tier 3 (loading index ≥0.66).

RESULTS

The single-leg decline squat showed the highest loading index (0.747). Other tier 3 exercises included single-leg forward hop (0.666), single-leg countermovement jump (0.711), and running cut (0.725). The Spanish squat was categorized as a tier 2 exercise (0.563), as was running (0.612), double-leg countermovement jump (0.610), single-leg drop vertical jump (0.599), single-leg full squat (0.580), double-leg drop vertical jump (0.563), lunge (0.471), double-leg full squat (0.428), single-leg 60° squat (0.411), and Bulgarian squat (0.406). Tier 1 exercises included 20 cm step up (0.187), 20 cm step down (0.288), 30 cm step up (0.321), and double-leg 60° squat (0.224).

CONCLUSIONS

Three patellar tendon loading tiers were established based on a combination of loading peak, loading impulse, and loading rate. Clinicians may use these loading tiers as a guide to progressively increase patellar tendon loading during the rehabilitation of patients with patellar tendon disorders and after anterior cruciate ligament reconstruction using the bone-patellar tendon-bone graft.

Falling decreased anterior cruciate ligament loading variables during single-leg landings after mid-flight external trunk perturbation

Mid-flight external upper-trunk perturbation is associated with increased anterior cruciate ligament (ACL) injury risk during landing. This study aimed to assess the effect of natural, soft, and falling landing techniques on knee mechanics and vertical ground reaction forces (VGRF) during single-leg landings with/without mid-flight medial-lateral external upper-trunk pushing perturbation. Twenty-eight participants performed single-leg landings using the three landing techniques with/without mid-flight pushing perturbation. The perturbation was created by a customized apparatus releasing a slam ball and pushing the participants near the peak jump height at the upper trunk. Perturbation resulted in significantly greater lateral trunk bending angles, knee flexion angles at initial contact, peak knee abduction angles, and peak knee adduction moments compared to no perturbation. The falling condition significantly demonstrated the greatest lateral trunk bending angles, knee flexion angles, and peak knee external rotation moments and the smallest peak knee abduction angles, peak VGRF, and peak knee extension moments compared to natural/soft landings regardless of perturbation conditions. Mid-flight external perturbation resulted in variables associated with greater ACL loading during single-leg landings. Falling demonstrated variables associated with smaller ACL loading, particularly for perturbation conditions. Incorporating falling techniques into jump-landing training programs may guide players to safely fall on the ground when perturbation occurs. Falling provides an alternative strategy to potentially decrease indirect contact ACL injury risk when the sports environment allows.

Increasing Breast Support is Associated With a Distal-to-Proximal Redistribution of Joint Negative Work During a Double-Limb Landing Task

Female athletes exhibit greater rates of anterior cruciate ligament injury compared with male athletes. Biomechanical factors are suggested to contribute to sex differences in injury rates. No previous investigation has evaluated the role of breast support on landing biomechanics. This study investigates the effect of breast support on joint negative work and joint contributions to total negative work during landing. Thirty-five female athletes performed 5 landing trials in 3 breast support conditions. Lower-extremity joint negative work and relative joint contributions to total negative work were calculated. Univariate analyses of variance were used to determine the effect of breast support on negative joint work values. Increasing levels of breast support were associated with lower ankle negative work (P < .001) and ankle relative contributions (P < .001) and increases in hip negative work (P = .008) and hip relative contributions (P < .001). No changes were observed in total negative work (P = .759), knee negative work (P = .059), or knee contributions to negative work (P = .094). These data demonstrate that the level of breast support affects lower-extremity biomechanics. The distal-to-proximal shift in negative joint work and relative joint contributions may be indicative of a more protective landing strategy for anterior cruciate ligament injuries.

Incline and decline running alters joint moment contributions but not peak support moments in individuals with an anterior cruciate ligament reconstruction and controls

Individuals with an anterior cruciate ligament reconstruction (ACLR) commonly exhibit altered gait patterns, potentially contributing to an increased risk of osteoarthritis (OA). Joint moment contributions (JMCs) and support moments during incline and decline running are unknown in healthy young adults and individuals with an ACLR. Understanding these conditional joint-level changes could explain the increased incidence of OA that develops in the long term. Therefore, this knowledge may provide insight into the rehabilitation and prevention of OA development. We aimed to identify the interlimb and between-group differences in peak support moments and subsequent peak ankle, knee, and hip JMCs between individuals with an ACLR and matched controls during different sloped running conditions. A total of 17 individuals with unilateral ACLR and 17 healthy individuals who were matched based on sex, height, and mass participated in this study. The participants ran on an instrumented treadmill at an incline of 4°, decline of 4°, incline of 10°, and decline of 10°. The last 10 strides of each condition were used to compare the whole-stance phase support moments and JMCs between limbs, ACLR, and control groups and across conditions. No differences in JMCs were identified between limbs or between the ACLR and healthy control groups across all conditions. Support moments did not change among the different sloped conditions, but JMCs significantly changed. Specifically, ankle and knee JMCs decreased and increased by 30% and 33% from an incline of 10° to a decline of 10° running. Here, the lower extremities can redistribute mechanics across the ankle, knee, and hip while maintaining consistent support moments during incline and decline running. Our data provide evidence that those with an ACLR do not exhibit significant alterations in joint contributions while running on sloped conditions compared to the matched controls. Our findings inform future research interested in understanding the relationship between sloped running mechanics and the incidence of deleterious acute or chronic problems in people with an ACLR.

Accurately and effectively predict the ACL force: Utilizing biomechanical landing pattern before and after-fatigue

BACKGROUND AND OBJECTIVE

As a fundamental exercise technique, landing can commonly be associated with anterior cruciate ligament (ACL) injury, especially during after-fatigue single-leg landing (SL). Presently, the inability to accurately detect ACL loading makes it difficult to recognize the risk degree of ACL injury, which reduces the effectiveness of injury prevention and sports monitoring. Increased risk of ACL injury during after-fatigue SL may be related to changes in ankle motion patterns. Therefore, this study aims to develop a highly accurate and easily implemented ACL force prediction model by combining deep learning and the explored relationship between ACL force and ankle motion pattern.

METHODS

First, 56 subjects' during before and after-fatigue SL data were collected to explore the relationship between the ankle initial contact angle (AIC), ankle range of motion (AROM) and peak ACL force (PAF). Then, the musculoskeletal model was developed to simulate and calculate the ACL force. Finally, the ACL force prediction model was constructed by combining the explored relationship and sparrow search algorithm (SSA) to optimize the extreme learning machine (ELM) and long short-term memory (LSTM).

RESULTS

There was almost a stronger linear relationship between the PAF and AIC (R = -0.70), AROM (R2 = -0.61). By substituting AIC and AROM as independent variables in the SSA-ELM prediction model, the model shows excellent prediction performance because of very strong correlation (R2 = 0.9992,  MSE = 0.0023,  RMSE = 0.0474). Based on the equal scaling by combining results of SSA-ELM and SSA-LSTM, the prediction model achieves excellent performance in ACL force prediction of the overall waveform (R2 = 0.9947,  MSE = 0.0076,  RMSE = 0.0873).

CONCLUSION

By increasing the AIC and AROM during SL, the lower limb joint energy dissipation can be increased and the PAF reduced, thus reducing the impact loads on the lower limb joints and reducing ACL injuries. The proposed ACL dynamic load force prediction model has low input variable demands (sagittal joint angles), excellent generalization capabilities and superior performance in terms of high accuracy. In the future, we plan to use it as an accurate ACL injury risk assessment tool to promote and apply it to a wider range of sports training and injury monitoring.

The effect of dual-task on jump landing kinematics and kinetics in female athletes with or without dynamic knee valgus

It has been indicated that dual tasks may multiply the possibility of injuries due to divided attention. This study aimed to investigate the effect of dual-task on kinematics and kinetics of jump landing in female athletes with and without dynamic knee valgus. In this study, 32 recreational athletes between 18 and 30 years old were recruited and divided into with (n = 17) and without (n = 15) dynamic knee valgus groups. The 3-D positions of retroreflective markers were recorded at 200 Hz using a 8-camera Kestrel system (Motion Analysis Corporation, Santa Rosa, CA), while ground reaction forces were synchronously recorded at 1000 Hz using 2 adjacent force plates (FP4060-NC; Bertec Corporation, Columbus, OH). Kinematics and kinetics of jump landing were recorded while counting backward digits as a dual task, and also without counting backward digits as a single task. One-way repeated measures of variance were used to analyse data at the significant level of 95% (α < 0.05). The study found that the dual-task affected the angles and moments of hip, knee, and ankle joints (P < 0.05) in both groups. Additionally, the effect of the dual-task differed significantly between the two groups in the angles hip flexion (P < 0.001), knee abduction (P < 0.001), and ankle internal rotation (P = 0.001), as well as the moments hip flexion (P < 0.001), hip abduction (P = 0.011), knee flexion (P = 0.017), knee internal rotation (P < 0.001), ankle dorsiflexion (P = 0.046), ankle eversion (P < 0.001), and ankle internal rotation (P = 0.046). Athletes with dynamic knee valgus may have been less able to protect themselves during the landing and are more prone to lower extremities injuries. As a result, using kinematics and kinetics in athletes with dynamic knee valgus during landing may help identify potential mechanisms associated with risk factors of lower extremity injuries and ACL injuries as well.

Model-based estimation of muscle and ACL forces during turning maneuvers in alpine skiing

In alpine skiing, estimation of the muscle forces and joint loads such as the forces in the ACL of the knee are essential to quantify the loading pattern of the skier during turning maneuvers. Since direct measurement of these forces is generally not feasible, non-invasive methods based on musculoskeletal modeling should be considered. In alpine skiing, however, muscle forces and ACL forces have not been analyzed during turning maneuvers due to the lack of three dimensional musculoskeletal models. In the present study, a three dimensional musculoskeletal skier model was successfully applied to track experimental data of a professional skier. During the turning maneuver, the primary activated muscles groups of the outside leg, bearing the highest loads, were the gluteus maximus, vastus lateralis as well as the medial and lateral hamstrings. The main function of these muscles was to generate the required hip extension and knee extension moments. The gluteus maximus was also the main contributor to the hip abduction moment when the hip was highly flexed. Furthermore, the lateral hamstrings and gluteus maximus contributed to the hip external rotation moment in addition to the quadratus femoris. Peak ACL forces reached 211 N on the outside leg with the main contribution in the frontal plane due to an external knee abduction moment. Sagittal plane contributions were low due to consistently high knee flexion (> 60[Formula: see text]), substantial co-activation of the hamstrings and the ground reaction force pushing the anteriorly inclined tibia backwards with respect to the femur. In conclusion, the present musculoskeletal simulation model provides a detailed insight into the loading of a skier during turning maneuvers that might be used to analyze appropriate training loads or injury risk factors such as the speed or turn radius of the skier, changes of the equipment or neuromuscular control parameters.

Jump-landing kinetic asymmetries persisted despite symmetric squat kinetics in collegiate athletes following anterior cruciate ligament reconstruction

The purpose was to determine the differences/correlations in anterior cruciate ligament (ACL) loading variables and bilateral asymmetries between injured/uninjured legs and among ascending/descending phases of double-leg squats and jumping/landing phases of countermovement jumps (CMJ) in the collegiate athletes following ACL reconstruction (ACLR). Fourteen collegiate athletes performed squats and CMJ 6-14 months following ACLR. The bilateral knee/hip flexion angles, peak vertical ground reaction force (VGRF) and knee extension moments (KEM), and kinetic asymmetries were calculated. Squats showed the greatest knee/hip flexion angles, while the landing phase of CMJ showed the least (P<0.001). The uninjured leg demonstrated greater VGRF (P≤0.010) and KEM (P≤0.008) than the injured leg in CMJ. Kinetic asymmetries were less than 10% for squats but were greater for the jumping (P≤0.014, 12%-25%) and landing (P≤0.047, 16%-27%) phases of CMJ. Significant correlations were found for KEM asymmetries between phases of CMJ (P=0.050) and squats (P<0.001). Kinetic asymmetries persisted in CMJ, while kinetic symmetries were achieved in squats in collegiate athletes 6-14 months following ACLR. Therefore, the CMJ appears to be a more sensitive assessment to monitor the bilateral kinetic asymmetries compared to squats. It is suggested to assess and screen kinetic asymmetries in different phases and tasks.

Curves and kinematics: Relationship between the force-time curve and landing ability

Anterior cruciate ligament (ACL) injuries have a significant impact on athletic performance and long-term quality of life. Force plates and qualitative screening tools are feasible and effective screening methods to identify abnormal movement quality associated with increased injury risk. Comparing qualitative assessments of landing ability with force-time curves, may detect unique differences between safe and high-risk athletic movement patterns. The aim of this study was to determine low- and high-risk landing ability from qualitive landing assessments and to examine the resulting force-time curves using functional principal component analysis (fPCA). Thirty-one healthy academy athletes (10 males and 21 females) completed double- and single-leg dominant and non-dominant jump-landing-rebound tasks. All movements were filmed in multiple-planes, and vertical ground reaction forces (vGRF) were simultaneously collected. The Landing Error Scoring System (LESS) and Single-Leg Landing Error Scoring System (SL-LESS) were used to score landing footage. From these scores, athletes were categorized into low-risk and high-risk groups for further analysis. fPCA was used to examine differences between landing quality groups force-time curves. Compared to high-risk landers, low-risk landers demonstrated significantly longer contact times across all movements. Scores from fPC1 revealed safe and high-risk landing techniques expose athletes to significantly different loading patterns during double- and single-leg dominant movements. A significant positive relationship was observed between fPC1 and LESS scores, however this relationship was not observed in both single-leg landing scores. Where possible incorporating curve analysis methods like fPCA into multi-faceted screening approaches may help practitioners uncover unique insights into athletic loading strategies.

Effect of sprinting velocity on anterior cruciate ligament and knee load during sidestep cutting

The purpose of the study was to investigate the effect of an increase in sprinting velocity on the anterior cruciate ligament (ACL) load, knee joint load, and activation of femoral muscles using the musculoskeletal modeling approach. Fourteen high school male athletes were recruited (age: 17.4 ± 0.7 years, height: 1.75 ± 0.04 m, weight: 73.3 ± 8.94 kg), with the right foot dominant and physical activity level of about 3-4 h per day. The kinematics, kinetics, and co-contraction index (CCI) of the extensors and flexors of the right leg's femoral muscles were calculated. The anterior cruciate ligament load was estimated using the musculoskeletal modeling method. In the results, it was observed that the anterior cruciate ligament load (p < 0.017) increased as sidestep cutting velocity increased, resulting in increased adduction (p < 0.017) and the internal rotation moment of the knee joint. This was significantly higher than when sprinting at a similar velocity. The co-contraction index result, which represents the balanced activation of the femoral extensor and flexor muscles, showed a tendency of decrement with increasing sprinting velocity during sidestep cutting (p < 0.017), whereas no significant differences were observed when running at different sprinting conditions. Therefore, we postulate that factors such as knee joint shear force, extended landing posture with increasing sprinting velocity, internal rotation moment, and femoral muscle activity imbalance influence the increase of anterior cruciate ligament load during a sidestep cutting maneuver.

Prelanding Knee Kinematics and Landing Kinetics During Single-Leg and Double-Leg Landings in Male and Female Recreational Athletes

Biomechanical behavior prior to landing likely contributes to anterior cruciate ligament (ACL) injuries during jump-landing tasks. This study examined prelanding knee kinematics and landing ground reaction forces (GRFs) during single-leg and double-leg landings in males and females. Participants performed landings with the dominant leg or both legs while kinematic and GRF data were collected. Single-leg landings demonstrated less time between prelanding minimal knee flexion and initial ground contact, decreased prelanding and early-landing knee flexion angles and velocities, and increased peak vertical and posterior GRFs compared with double-leg landings. Increased prelanding knee flexion velocities and knee flexion excursion correlated with decreased peak posterior GRFs during both double-leg and single-leg landings. No significant differences were observed between males and females. Prelanding knee kinematics may contribute to the increased risk of ACL injuries in single-leg landings compared with double-leg landings. Future studies are encouraged to incorporate prelanding knee mechanics to understand ACL injury mechanisms and predict future ACL injury risks. Studies of the feasibility of increasing prelanding knee flexion are needed to understand the potential role of prelanding kinematics in decreasing ACL injury risk.

The Mechanism of Anterior Cruciate Ligament Injuries in the National Football League: A Systematic Video Review

Introduction Anterior cruciate ligament (ACL) injuries are common among American football athletes, although few studies have performed video analyses of ACL injuries to better understand the injury mechanism. This work aims to characterize the mechanism of ACL injury during professional football competitions using video analysis. We hypothesize that football-specific injury trends will emerge, including high rates of contact injuries and associations with shallow knee and hip flexion angles (0°-30°). Methods Videos of professional football players suffering ACL injuries from 2007 to 2016 were analyzed. Injured players were identified using the injured reserve (IR) lists of the National Football League (NFL), and videos were discovered via a systematic Google search. Descriptive statistics and frequency analyses were performed on all variables using the Statistical Package for the Social Sciences (SPSS) version 23.0 (IBM SPSS Statistics, Armonk, NY, USA). Results Of the 429 ACL injuries identified, 53 (12%) videos were available. Deceleration was the most common injury maneuver, present in 32 (60%) athletes. Thirty-one (58%) players suffered contact injuries. Twenty-eight (53%) injuries demonstrated valgus collapse of the knee, and 26 (49%) had neutral knee rotation. Defensive backs (26%) and wide receivers (23%) were the most frequently injured positions. Conclusion Overall, we found that most ACL injuries had preceding contact, deceleration, shallow hip and knee flexion, and heel strike, and subsequent valgus collapse and neutral knee rotation. This understanding of American football-specific ACL tear mechanisms could help direct the focus of future injury prevention training modalities.

Asymmetries in Two-Dimensional Trunk and Knee Kinematics During a Single-Leg Drop Landing Post Anterior Cruciate Ligament Reconstruction

The purpose of this study was to compare interlimb asymmetries in trunk and knee kinematics during a single-leg drop landing between athletes 9 months post anterior cruciate ligament reconstruction (post-ACLR) and healthy athletes using two-dimensional analysis. Thirty-three recreational athletes (12 post-ACLR and 21 healthy) participated in the study. Participants post-ACLR showed significantly higher limb symmetry indices in peak trunk flexion (144.0%, SE drop landing kinematics: 22.7%) when compared to healthy participants (100.6%, SE: 10.5%; z = 2.17, p = .03) and lower limb symmetry indices in peak knee flexion (85.3%, SE: 3.6%) when compared to healthy participants (98.0%, SE: 3.3%; z = −2.43, p = .01). Two-dimensional analyses of a single-leg drop landing is a clinically applicable tool that can identify interlimb asymmetries in peak trunk flexion and peak knee flexion kinematics in athletes greater than 9 months post-ACLR when compared to healthy athletes.

Indirect contact matters: Mid-flight external trunk perturbation increased unilateral anterior cruciate ligament loading variables during jump-landings

BACKGROUND

To determine the effect of unanticipated mid-flight medial-lateral external perturbation of the upper or lower trunk on anterior cruciate ligament (ACL) loading variables during jump-landings.

METHODS

Thirty-two participants performed double-leg vertical jump-landings while bilateral kinematics and kinetics were collected under 6 conditions (upper or lower trunk perturbation locations; no, left, or right perturbation directions). Two customized catapult apparatuses were created to apply pushing perturbation to participants near the maximal jump height.

RESULTS

The ball contacted participants near the center of mass for the lower-trunk conditions and approximately 23 cm above the center of mass for the upper-trunk conditions. Under upper-trunk perturbation, the contralateral leg demonstrated significantly smaller knee flexion angles at initial contact and greater peak knee abduction angles, peak vertical ground reaction forces, peak knee extension moments, and peak knee adduction moments compared to other legs among all conditions. Under lower-trunk perturbation, the contralateral leg showed significantly smaller knee flexion angles at initial contact and increased peak vertical ground reaction forces and peak knee extension moments compared to legs in the no-perturbation conditions.

CONCLUSION

Mid-flight external trunk pushing perturbation increased ACL loading variables for the leg contralateral to the perturbation. The upper-trunk perturbation resulted in greater changes in ACL loading variables compared to the lower-trunk perturbation, likely due to trunk and ipsilateral leg rotation and more laterally located center of mass relative to the contralateral leg. These findings may help us understand the mechanisms of indirect-contact ACL injuries and develop jump-landing training strategies under mid-flight trunk perturbation to better prevent ACL injury.

Analysis of Functional Arch Support Insoles on the Biomechanics and Performance in Right-Forward Lunging Step of Badminton Players

The purpose of this study was to examine the differences in biomechanical parameters and sports-specific performance of lower limbs between arch support insoles (ASI) and flat insoles (FLI) when performing net strides. After installing the MVN IMU system, 18 college badminton team members were asked to take the following tests: (1) Consecutive net stride tests; (2) Six-point footwork tests; (3) Retrieve/stroke the ball at the left and right net; (4) Smash and retrieve/stroke the ball at the net; (5) Smash at the front and back crossover step. The joint angle of the lower limbs and ground reaction force during the support phase was collected. The results demonstrated that the peak right hip flexion angle was significantly greater with ASI than FLI (63.09 ± 10.70; 60.08 ± 13.82; p = 0.028), while the peak right foot inversion angle was significantly smaller with ASI than FLI (20.68 ± 7.87; 23.85 ± 8.11; p = 0.013). The principal conclusion was that the arch support insole avoids the decrease in the hip flexion angle and the increase in the foot inversion angle during the net stride tests.

Kinematic Differences Between the Dominant and Nondominant Legs During a Single-Leg Drop Vertical Jump in Female Soccer Players

BACKGROUND

In soccer, the roles of the dominant (kicking) and nondominant (supporting) legs are different. The kinematic differences between the actions of the dominant and nondominant legs in female soccer players are not clear.

PURPOSE

To clarify the kinematic differences between dominant and nondominant legs during a single-leg drop vertical jump (DVJ) in female soccer players.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 64 female high school and college soccer players were included in this study. Participants performed a single-leg DVJ test utilizing video motion capture with artificial intelligence during the preseason period. This study assessed the knee flexion angles, knee valgus angles, hip flexion angles, and lower leg anterior inclination angle at 3 time points (initial contact, maximum flexion of the knee, and toe-off) and compared them between the dominant and nondominant legs. These angles were calculated from motion capture data and analyzed in 3 dimensions. A paired t test was used to analyze the differences between legs, and the significance level was set at P < .05.

RESULTS

The knee valgus angle at initial contact was greater in the nondominant leg (mean ± SD, 0.8°± 5.2°) than the dominant leg (-0.9°± 4.9°) (P < .01). There were no differences between legs for any other angles at any of the time points.

CONCLUSION

The kinematics of the dominant and nondominant legs of female soccer players in a single-leg DVJ differ in knee valgus angle.

CLINICAL RELEVANCE

Leg dominance is associated with the risk of sports injuries. Kinematic differences between the dominant and nondominant legs may be a noteworthy factor in elucidating the mechanisms and risk of sports injury associated with leg dominance.

Estimation of Joint Moments During Turning Maneuvers in Alpine Skiing Using a Three Dimensional Musculoskeletal Skier Model and a Forward Dynamics Optimization Framework

In alpine skiing, estimation of the joint moments acting onto the skier is essential to quantify the loading of the skier during turning maneuvers. In the present study, a novel forward dynamics optimization framework is presented to estimate the joint moments acting onto the skier incorporating a three dimensional musculoskeletal model (53 kinematic degrees of freedom, 94 muscles). Kinematic data of a professional skier performing a turning maneuver were captured and used as input data to the optimization framework. In the optimization framework, the musculoskeletal model of the skier was applied to track the experimental data of a skier and to estimate the underlying joint moments of the skier at the hip, knee and ankle joints of the outside and inside leg as well as the lumbar joint. During the turning maneuver the speed of the skier was about 14 m/s with a minimum turn radius of about 16 m. The highest joint moments were observed at the lumbar joint with a maximum of 1.88 Nm/kg for lumbar extension. At the outside leg, the highest joint moments corresponded to the hip extension moment with 1.27 Nm/kg, the knee extension moment with 1.02 Nm/kg and the ankle plantarflexion moment with 0.85 Nm/kg. Compared to the classical inverse dynamics analysis, the present framework has four major advantages. First, using a forward dynamic optimization framework the underlying kinematics of the skier as well as the corresponding ground reaction forces are dynamically consistent. Second, the present framework can cope with incomplete data (i.e., without ground reaction force data). Third, the computation of the joint moments is less sensitive to errors in the measurement data. Fourth, the computed joint moments are constrained to stay within the physiological limits defined by the musculoskeletal model.

Predicting neuromuscular control patterns that minimize ACL forces during injury prone jump landing maneuvers in downhill skiing using a musculoskeletal simulation model

Competitive skiers encounter a high risk of sustaining an ACL injury during jump-landing in downhill ski racing. Facing an injury-prone landing manoeuvre, there is a lack of knowledge regarding optimum control strategies. So, the purpose of the present study was to investigate possible neuromuscular control patterns to avoid injury during injury-prone jump-landing manoeuvres. A computational approach was used to generate a series of 190 injury-prone jump-landing manoeuvres based on a 25-degree-of-freedom sagittal plane musculoskeletal skier model. Using a dynamic optimization framework, each injury-prone landing manoeuvre was resolved to identify muscle activation patterns of the lower limbs and corresponding kinematic changes that reduce peak ACL force. In the 190 injury-prone jump-landing simulations, ACL forces peaked during the first 50 ms after ground contact. Optimized muscle activation patterns, that reduced peak ACL forces, showed increased activation of the monoarticular hip flexors, ankle dorsi- and plantar flexors as well as hamstrings prior to or during the early impact phase (<50 ms). The corresponding kinematic changes were characterized by increased hip and knee flexion and less backward lean of the skier at initial ground contact and the following impact phase. Injury prevention strategies should focus on increased activation of the monoarticular hip flexors, ankle plantar flexors and rapid and increased activation of the hamstrings in combination with a flexed landing position and decreased backward lean to reduce ACL injury risk during the early impact phase (<50 ms) of jump landing.HighlightsFirst study investigating advantageous control strategies during injury-prone jump-landing manoeuvres in downhill skiing using a musculoskeletal simulation model and dynamic optimization framework.The simulation results predicted high injury risk during the first 50 ms after initial ground contact.Optimized neuromuscular control patterns showed adapted activation patterns (timing and amplitude) of muscles crossing the knee as well as the hip and ankle joints prior to and after initial ground contact, respectively.An optimized control strategy during an injury-prone landing manoeuvre was characterized kinematically by increasing hip and knee flexion and less backward lean of the skier at initial ground contact and the following impact phase.

EFFECTS OF A PROPHYLACTIC KNEE SLEEVE ON THE ANTERIOR CRUCIATE LIGAMENT AND LOWER EXTREMITY BIOMECHANICS: AN EXAMINATION USING MUSCULOSKELETAL SIMULATION

The current study aimed using a two-experiment musculoskeletal simulation-based approach, measuring anterior cruciate ligament (ACL) biomechanics, knee joint kinematics, and lower extremity joint loading to examine the effects of both a prophylactic knee sleeve on (1) a sport-specific change of direction movement in female footballers and (2) a single leg landing in male footballers. Experiment 1 examined 12 female university first team level footballers (age [Formula: see text] years, height [Formula: see text][Formula: see text]m, body mass [Formula: see text][Formula: see text]kg) undertaking a [Formula: see text] cutting movement in sleeve and no-sleeve conditions. Experiment 2 examined 10 male university first team level footballers (age [Formula: see text] years, height [Formula: see text][Formula: see text]m, body mass [Formula: see text][Formula: see text]kg) undertaking a single leg drop jump landing in sleeve and no-sleeve conditions. In each experiment, data was collected in a biomechanics laboratory and three-dimensional (3D) motion capture and ground reaction force (GRF) information was collected. 3D kinematics, 3D knee kinetics, and ACL ligament forces/strains were measured using musculoskeletal simulation, and participants were also asked to subjectively rate the knee sleeve in terms of both comfort and stability. Experiment 1 showed that the sleeve condition was associated with greater ACL strain ([Formula: see text]% and no-[Formula: see text]%) and forces ([Formula: see text] BW and no-[Formula: see text] BW). In addition, the brace condition also enhanced lateral compressive tibiofemoral ([Formula: see text] BW and no-[Formula: see text] BW) and total compressive tibiofemoral force ([Formula: see text] BW and no-[Formula: see text] BW). Finally, for the subjective ratings, participants indicated that the knee sleeve significantly improved perceived comfort and stability. Experiment 2 did not reveal any statistical differences between knee sleeve and no-sleeve conditions nor any effects of the knee sleeve on subjective ratings of comfort or stability. Therefore, the findings from the current investigation suggest that the prophylactic knee sleeve examined in the current investigation does not appear to reduce the biomechanical parameters linked to the aetiology of knee pathologies in male/female footballers.

The effects of virtual reality immersion on drop landing mechanics

Virtual reality (VR) can be used to alter the environment and challenge sensory calibration which rehabilitation and return-to-sport testing lack. The purpose was to establish how VR manipulation of the environment changes knee landing biomechanics. Twenty-nine healthy active adults (22 males; 20.52 ± 1.21 years; 1.75 ± 0.09 m; 78.34 ± 14.33 kg) were recruited. Three drop landing trials (31 cm height box) were performed for three conditions: eyes-open (EO), eyes-closed (EC), and VR, consisting of a head-mounted display of a 360° photo of a steep man-made edge or drop. Knee kinematics and kinetics were evaluated using 3D motion capture. The VR condition significantly increased Landing Error Score System errors relative to EO (1.28 ± 0.20, p < 0.001) and EC (0.98 ± 0.22, p < 0.001) and increased vertical ground reaction force relative to EO (0.41 ± 0.09 N·bw-1, p < 0.001) and EC (0.34 ± 0.07 N·bw-1, p < 0.001). The VR condition had less knee flexion at initial contact compared to EO (4.39 ± 0.75°, p = 0.001) and EC (1.83 ± 0.63°, p = 0.021). The VR condition had more knee abduction at initial contact compared to EO (0.71 ± 0.24°, p = 0.002) and EC (0.69 ± 0.22°, p = 0.002) and increased knee abduction at maximum flexion compared to EO (2.01 ± 0.58°, p = 0.026). Landing in VR increased injury risk landing biomechanics, indicating that VR may option to incorporate into return-to-play or injury risk assessment.

Exercise-Based Training Strategies to Reduce the Incidence or Mitigate the Risk Factors of Anterior Cruciate Ligament Injury in Adult Football (Soccer) Players: A Systematic Review

Anterior cruciate ligament (ACL) is one of the most concerning injuries for football players. The aim of this review is to investigate the effects of exercise-based interventions targeting at reducing ACL injury rate or mitigating risk factors of ACL injury in adult football players. Following PRISMA guidelines, a systematic search was conducted in CINAHL, Cochrane Library, PubMed, Scopus, SPORTDiscus and Web of Science. Studies assessing the effect of exercise-based interventions in ACL injury incidence or modifiable risk factors in adult football players were included. 29 studies evaluating 4502 male and 1589 female players were included (15 RCT, 8 NRCT, 6 single-arm): 14 included warm-up, 7 resistance training, 4 mixed training, 3 balance, 1 core stability and 1 technique modification interventions. 6 out of 29 studies investigated the effect of interventions on ACL injury incidence, while the remaining 23 investigated their effect on risk factors. Only 21% and 13% studies evaluating risk of injury variables reported reliability measures and/or smallest worthwhile change data. Warm-up, core stability, balance and technique modification appear effective and feasible interventions to be included in football teams. However, the use of more ecologically valid tests and individually tailored interventions targeting specific ACL injury mechanisms are required.

Regression model for predicting knee flexion angles using ankle plantar flexion angles, body mass index and generalised joint laxity

Increased knee flexion angles are associated with reduced non-contact anterior cruciate ligament (ACL) injury risks. Ankle plantar flexion angles and internal risk factors could influence knee flexion angles, but their correlations are unknown. This study aimed to establish and validate a regression model to predict knee flexion angles using ankle plantar flexion angles, body mass index (BMI) and generalised joint laxity (GJL) at initial contact of single-leg drop landings. Thirty-two participants performed single-leg drop landings from a 30-cm-high platform. Kinematics and vertical ground reaction forces were measured using a motion capture system and force plate. A multiple regression was performed, and it was validated using a separate data set. The prediction model explained 38% (adjusted R2) of the change in knee flexion angles at initial contact (p = 0.001, large effect size). However, only the ankle plantar flexion angle (p < 0.001) was found to be a significant predictor of knee flexion angles. External validation further showed that the model explained 26% of knee flexion angles (large effect size). The inverse relationship between ankle plantar flexion and knee flexion angles suggests that foot landing strategies could be used to increase knee flexion angles, thereby reducing non-contact ACL injury risks.

The effects of sex and landing task on hip mechanics

Prevalence of femoroacetabular impingement syndrome is common in cutting sports. A first step to understanding the relationship between cutting sports and the development of femoroacetabular impingement is to investigate hip joint contact forces during such tasks. The purpose of this study was to explore sex and task differences in hip joint contact forces, estimated through musculoskeletal modeling, during single-leg drop landings and land-and-cuts. Kinematics and ground reaction forces were obtained from 38 adults performing drop landings and land-and-cut tasks. Simulations were performed in OpenSim to estimate lower extremity muscle forces and hip joint contact forces. Statistical parametric mapping was used to compare hip joint force waveforms between sex and task. There were no sex differences in hip joint forces, but landing trials were characterized by increased hip joint forces compared to land-and-cut trials. The hip joint force estimates obtained the current study could be used in future finite element models that incorporate bone growth models to understand the development of femoroacetabular impingement and design possible compensatory exercises.

Estimation of vertical ground reaction force parameters during athletic tasks using 2D video

BACKGROUND

Given that elevated vertical ground reaction forces (vGRF) have been reported to contribute to various lower-extremity injuries, there is a need for a practical method to characterize movement behavior that is representative of elevated impact forces.

RESEARCH QUESTION

Can images obtained from 2D video be used to predict vGRF parameters during athletic tasks? Specifically, we sought to determine whether the 2D thigh angle obtained at peak knee flexion could be used to predict the peak vGRF and vGRF impulse during single limb and double limb landings and movements that involve a change of direction.

METHODS

2D sagittal plane video and vGRFs were obtained simultaneously from 39 participants (15 males and 24 females) during 5 athletic tasks (drop jump, lateral shuffle, deceleration, triple hop, side-step-cut). Linear regression analysis was performed to determine if the 2D thigh angle at peak knee flexion predicted the first peak of the vGRF and vGRF impulse during the deceleration phase of each task.

RESULTS

The 2D thigh angle predicted the peak vGRF for all tasks except cutting (R² = 0.17 to 0.47, all p < 0.01). However, the 2D thigh angle predicted the vGRF impulse for all 5 tasks (R² = 0.13 to 0.39, all p < 0.025).

SIGNIFICANCE

An increased 2D thigh angle (which is representative of increased hip and knee flexion) was able to predict lower peak vGRFs and vGRF impulse during athletic tasks. The 2D thigh angle is a potential clinical method to characterize movement behavior that may expose individuals to high impact forces.

Kinetic changes associated with extended knee landings following anterior cruciate ligament reconstruction in females

OBJECTIVES

To determine the relationship between knee flexion excursion symmetry and lower extremity kinematics, kinetics, and muscle, joint, and ligament forces in females 1-3 years after ACL reconstruction.

DESIGN

Cross-sectional.

SETTING

Laboratory.

PARTICIPANTS

Twenty-one, college-aged females.

MAIN OUTCOME MEASURES

Lower extremity kinetics and kinematics, including estimated muscle, tibiofemoral, and ligament forces were assessed using 3D motion analysis and a musculoskeletal modeling approach. Participants demonstrating greater than 10% asymmetry in knee flexion excursion were classified as landing with an "extended knee". Group and between-limb differences were compared.

RESULTS

Ten participants were classified as landing with an "extended knee" on the involved limb, while eleven exhibited a symmetric landing pattern. Participants landing with an "extended knee" demonstrated reduced knee extension moment and quadriceps force in the involved limb (p < 0.05).

CONCLUSIONS

These findings indicate that an "extended knee" landing pattern was associated with reduced knee extension moment and quadriceps muscle force in females 1-3 years after ACL reconstruction. This may represent an altered strategy that clinicians may choose to identify and address during rehabilitation.

Changes in landing mechanics using augmented feedback: 4-Week training and retention study

CONTEXT

Non-contact ACL injuries are common in female athletes during landing tasks. Post-trial performance-based feedback may be an effective method to reduce landing forces and knee valgus during landing. Information regarding the retention of these changes based on such training is generally lacking for weekly and monthly retention.

OBJECTIVE

To determine the effectiveness of post-trial feedback training to promote and retain changes in vertical ground reaction force (vGRF) and knee to ankle (K:A) ratio during a dual task drop landing in female collegiate athletes.

DESIGN

Repeated measures; SETTING: University campus.

PARTICIPANTS

22 female collegiate athletes.

MATERIALS AND METHODS

Dual task drop landings were performed over 4 successive weeks with immediate post trial feedback on peak vGRF, symmetry, and K:A ratio. K:A ratio was a surrogate measure for knee valgus in drop landing.

RESULTS

Significant decreases in vGRF and increases in K:A ratio were found within training sessions (p = .000). Both variables were retained each week over the 4 weeks.

CONCLUSION

Using a custom portable clinical feedback system may be an effective tool in reducing peak vGRFs and knee abduction angles during a drop landing over a 4-week period in female collegiate athletes.

Establishing Normative Values for Inter-Limb Kinetic Symmetry During Landing in Uninjured Adolescent Athletes

BACKGROUND

Assessment of inter-limb kinetic symmetry during landing could provide valuable insights when working with athletes who have undergone anterior cruciate ligament reconstruction. However, it is difficult to determine if the asymmetry exhibited by an injured athlete is excessive or within a range that is similar to uninjured athletes, until normative values are established.

PURPOSE

The purpose of this study was to establish normative values for inter-limb impact force symmetry in uninjured adolescent athletes. In addition, an example is provided of how these normative values could be used to identify athletes who exhibit atypically high levels of asymmetry following anterior cruciate ligament reconstruction.

STUDY DESIGN

Cross-sectional study.

METHODS

One hundred and thirty-six uninjured athletes completed drop vertical jumps and countermovement jumps while force plates recorded ground reaction forces. Symmetry indices captured inter-limb symmetry in impact forces during landing for both tasks. These symmetry indices were also combined to create an index that captured symmetry across both tasks. Normative values were established using the uninjured athletes' data. Eleven athletes who had undergone anterior cruciate ligament reconstruction and been cleared to return to landing and jumping performed the same tasks and their data were compared to the results for the uninjured group.

RESULTS

Measures of central tendency, variability, percentiles, and outliers were calculated/identified based on the uninjured athletes' symmetry indices. Six of the 11 injured athletes exhibited atypically high symmetry index values.

CONCLUSION

The normative values established as part of this study may serve as a basis for identifying athletes who exhibit atypically high levels of inter-limb impact force asymmetry during jumping tasks following anterior cruciate ligament reconstruction.

LEVEL OF EVIDENCE

3b.

Lower limb kinematics differ at the time of foot contact between successful and unsuccessful single limb landings following anterior cruciate ligament reconstruction

OBJECTIVES

To investigate differences in lower extremity kinematics at initial ground contact between successful and unsuccessful single limb landings following anterior cruciate ligament (ACL) reconstruction.

DESIGN

Observational study.

SETTING

Controlled laboratory environment.

PARTICIPANTS

22 male participants (aged 17-40 years) who had undergone unilateral ACL reconstruction attended a single test session.

MAIN OUTCOME MEASURES

Within-subjects comparisons was performed for pelvis, hip, knee and ankle kinematics using paired t-tests.

RESULTS

When unsuccessful at landing on the ACL reconstructed limb, participants had significantly increased knee flexion (P = 0.04) and reduced ankle plantarflexion (P = 0.03) compared to their successful landings. In contrast, when unsuccessful at landing on the unaffected limb, participants had significantly increased pelvic contralateral hitch (P < 0.01) and increased hip abduction (P < 0.01) compared to successful landings.

CONCLUSION

Body position at the time of initial contact was different for landings that were successful compared to landings that were unsuccessful. These differences were limb-specific: altered position in sagittal plane preceded unsuccessful landings on the reconstructed limb whereas altered position in the coronal plane body position that preceded unsuccessful landings on the unaffected limb. These findings suggest that limb specific landing strategies may be required to improve athletes' performance following ACL reconstruction.

LEVEL OF EVIDENCE

IV.

Noncontact Knee Ligament Injury Prevention Screening in Netball: A Clinical Commentary with Clinical Practice Suggestions for Community-Level Players

Netball is a predominantly female team court-sport which is played worldwide. Netball is becoming more popular in the United States following its countrywide introduction to schools and community centers. A unique characteristic of netball is the footwork rule which restricts players to a one-step landing after catching the ball. Most netball landings are single-leg landings resulting in high vertical ground reaction forces and high skeletal tissue forces. Thus, high-risk landing events that have the biomechanical potential for injury occur frequently. Noncontact knee ligament injuries are common following a knee abduction collapse when landing. Because the consequences of noncontact knee ligament injury are profound, strategies are needed to mitigate the burden of such injury for players, teams, and society. The purpose of this clinical commentary is to demonstrate how theoretical principles, different types of research, and different levels of evidence underpin a rational clinical reasoning process for developing noncontact knee ligament injury prevention screening procedures in netball. The theoretical principles that are discussed in this commentary include injury control, the sequence of prevention, principles of screening in injury prevention, the multifactorial model of injury etiology, complex systems theory, and systems science. The different types of research that are reviewed include descriptive and analytic-observational studies. The different levels of evidence that are discussed include prospective studies, cross-sectional studies, and clinicians' own kinesiological modelling. Subsequently, an integrated approach to the evidence-informed development of noncontact knee ligament injury prevention screening procedures is presented. Clinical practice suggestions include a selection of evidence-informed screening tests that are quickly and easily implemented with netball players in local communities. The need for repeated screening at strategic timepoints across a season/year is explained. Sports physical therapists will find this commentary useful as an example for how to undertake clinical reasoning processes that justify the content of screening procedures contributing to noncontact knee ligament injury prevention in community-level netball.

LEVEL OF EVIDENCE

5.

On the impact force analysis of two-leg landing with a flexed knee

This article looks into the effects of the initial knee flexion angle at the contact time on the peak of the impulsive lower limb forces during landing, and how these effects are related to muscular activities. The impact dynamics of drop landing is studied via a musculoskeletal model with eight Hill-type lower-limb muscles. A method is proposed for the representation of two landing strategies: landing with high and low joint stiffness. Then, in each landing strategy, the effect of the initial knee flexion angle on the peak ground reaction force (GRF), the peak knee ligaments force and the peak tibiofemoral contact force is investigated by considering different initial contact postures. It is observed that while landing with a flexed knee decreases the peak GRF in both landing strategies, it decreases the peak tibiofemoral and knee ligaments forces only in landing with low joint stiffness. Specifically, by increasing the initial knee flexion from 0° to 70°, the peak tibiofemoral and knee ligaments forces decrease monotonically by 54% and 82%, in landing with low joint stiffness. For high joint stiffness, however, as the initial knee flexion increases from 10° to 70°, the peak tibiofemoral force is seen to increase monotonically by 42% and the peak knee ligaments force is seen to have a non-monotonic behavior, first decreasing by 42%, and then, increasing by 250%. These results can be considered in training landing strategies to reduce the risk of knee injury.

Investigating the landing kinetics factors and preparatory knee muscle activation in female handball players with and without dynamic knee valgus while performing single leg landing

Study aim: to examine the differences in landing kinetics factors (LKF) to assess the whole body stability and preparatory muscle activation (PMA) in female handball players with and without dynamic knee valgus.

Material and methods: Twenty-four professional female handball players (11 with (DKV) and 13 without (Control) dynamic knee valgus) were asked to perform three trials of a single-leg landing. LKF and surface EMG were recorded. Initial contact knee valgus angle (IC KVA), vertical ground reaction force (vGRF), confidence ellipse area of center of pressure (CEA), time to stability (TTS) and EMG from 100 ms prior to ground contact were used in the data analyses.

Results: Multivariate analyzing of LKF showed significant differences between two groups (p = 0.001) while for PMA the result was not significant (p = 0.361).

Conclusion: Altered landing mechanism considered as a predictor of non-contact knee injuries such as ACL rupture. Therefore according to current study it seems important to focus on reducing valgus angle in designing injury prevention program.

Recommendations for Movement Re-training After ACL Reconstruction

It is important to optimise the functional recovery process to enhance patient outcomes after major injury such as anterior cruciate ligament reconstruction (ACLR). Restoring movement quality during sporting-type movements is important prior to return-to-sport (RTS) after ACLR. Alterations in movement quality during an array of functional tasks are common amongst ACLR patients at or near the time of RTS and are associated with worse outcomes after ACLR. The inability to correct movement issues prior to RTS is likely due to the use of incomplete programmes or a lack of volume and intensity of movement re-training programmes. Although most clinicians and researchers understand that re-training movement after ACLR is important (e.g., the 'why'), there is often a disconnect with understanding the 'how' and 'what' of movement re-training post ACLR. The aim of this paper was to discuss factors relevant to movement dysfunction and re-training after ACLR and provide recommendations for clinicians to restore movement quality of patients after ACLR, prior to RTS. The paper recommends: (i) considering the factors which influence the expression of movement quality, which revolve around individual (e.g., neuromuscular, biomechanical, sensorimotor and neurocognitive factors), task-specific and environmental constraints; (ii) incorporating a three-staged movement re-training approach aligned to the ACLR functional recovery process: (1) addressing the neuromuscular and biomechanical and sensorimotor control factors which affect movement quality and motor learning, (2) including a progressive movement re-training approach to re-learn an array of functional tasks optimising coordination and motor learning (3) performing the final aspect of rehabilitation and movement training on the field, in realistic environments progressively simulating the sporting movement demands and environmental constraints; and (iii) effectively designing the movement programme for optimal load management, employing effective coach and feedback techniques and utilising qualitative movement analysis for transition between exercises, stages and for RTS.

A longitudinal investigation of landing biomechanics following anterior cruciate ligament reconstruction

OBJECTIVE

Abnormal movement patterns have been shown during landing in patients who have undergone anterior cruciate ligament (ACL) reconstruction surgery. The purpose of this study was to investigate landing biomechanics over time in this patient group to determine whether asymmetry between limbs reduced with time and after a return to physical activity.

DESIGN

Prospective longitudinal study.

SETTING

Biomechanics laboratory.

PARTICIPANTS

Fourteen patients who had undergone ACL reconstruction surgery.

MAIN OUTCOME MEASURE

Single limb landing assessments were made at two time points; within the first year (mean of 10 months) and at 3 years (after patients had returned to sport) following ACL reconstruction. Three-dimensional motion analysis was used to record kinematic and kinetic variables, which were compared across time and limb using ANOVA models.

RESULTS

Most biomechanical variables showed little change over time except for the external knee adduction moment at the operated knee, which increased (effect size d = 0.5), but remained less than the contralateral side. In the sagittal plane, asymmetrical landing patterns were seen at both assessments. Patients landed with reduced knee flexion angles (effect size range 0.76-0.9) and moments (effect size range 0.56-0.9) compared to the uninjured limb and made compensations for this by increasing the hip flexion moment (effect size range d = 0.6-0.75).

CONCLUSIONS

Asymmetrical landing biomechanics persisted at three years after ACL reconstruction in athletes who returned to sporting activity. Long term implications of controlling the landing by increasing the hip moment are unknown and require further investigation.

Anterior Cruciate Ligament Loading Increases With Pivot-Shift Mechanism During Asymmetrical Drop Vertical Jump in Female Athletes

Background:

Frontal plane trunk lean with a side-to-side difference in lower extremity kinematics during landing increases unilateral knee abduction moment and consequently anterior cruciate ligament (ACL) injury risk. However, the biomechanical features of landing with higher ACL loading are still unknown. Validated musculoskeletal modeling offers the potential to quantify ACL strain and force during a landing task.

Purpose:

To investigate ACL loading during a landing and assess the association between ACL loading and biomechanical factors of individual landing strategies.

Study Design:

Descriptive laboratory study.

Methods:

Thirteen young female athletes performed drop vertical jump trials, and their movements were recorded with 3-dimensional motion capture. Electromyography-informed optimization was performed to estimate lower limb muscle forces with an OpenSim musculoskeletal model. A whole-body musculoskeletal finite element model was developed. The joint motion and muscle forces obtained from the OpenSim simulations were applied to the musculoskeletal finite element model to estimate ACL loading during participants’ simulated landings with physiologic knee mechanics. Kinematic, muscle force, and ground-reaction force waveforms associated with high ACL strain trials were reconstructed via principal component analysis and logistic regression analysis, which were used to predict trials with high ACL strain.

Results:

The median (interquartile range) values of peak ACL strain and force during the drop vertical jump were 3.3% (–1.9% to 5.1%) and 195.1 N (53.9 to 336.9 N), respectively. Four principal components significantly predicted high ACL strain trials, with 100% sensitivity, 78% specificity, and an area of 0.91 under the receiver operating characteristic curve (P < .001). High ACL strain trials were associated with (1) knee motions that included larger knee abduction, internal tibial rotation, and anterior tibial translation and (2) motion that included greater vertical and lateral ground-reaction forces, lower gluteus medius force, larger lateral pelvic tilt, and increased hip adduction.

Conclusion:

ACL loads were higher with a pivot-shift mechanism during a simulated landing with asymmetry in the frontal plane. Specifically, knee abduction can create compression on the posterior slope of the lateral tibial plateau, which induces anterior tibial translation and internal tibial rotation.

Clinical Relevance:

Athletes are encouraged to perform interventional and preventive training to improve symmetry during landing.

Influence of Side Uncertainty on Knee Kinematics of Female Handball Athletes During Sidestep Cutting Maneuvers

Noncontact anterior cruciate ligament ruptures generally occur during unanticipated sidestep cutting maneuvers when athletes have their visual attention focused on the opponent. The authors investigated the influence of uncertainty related to the side to perform the sidestep cutting maneuver on knee kinematics of female handball athletes. A total of 31 female handball athletes performed the sidestep cutting maneuver during anticipated and uncertain conditions. During the uncertain condition, visual cues indicated the direction of the reactive sidestep cutting maneuver. Between-condition differences were compared using the Student t test for paired samples calculated with statistical parametric mapping. Lower knee flexion angle was detected during the uncertain condition compared with the anticipated condition for the nondominant limb (0%-8% of the sidestep cycle). Knee abduction was larger during the uncertain condition for both the dominant (15%-41% of the sidestep cycle) and nondominant (0%-18% of the sidestep cycle) limbs compared with the anticipated condition. The nondominant leg showed higher knee abduction (36%-68% of the sidestep cycle) during the uncertain condition compared with the anticipated condition. The athletes' approach velocity was slower during the uncertain condition. The uncertain condition impacted knee kinematics and potentially positioned the joint at greater risk of injury by decreasing the flexion angle in the nondominant leg and increasing the joint valgus bilaterally.

Reliability of 3D measurement of pelvic and lower limb kinematics during two single leg landing tasks

Study aim: Three-dimensional (3D) motion analysis is one of the available methods used to evaluate body kinematics. The aim of this study was to assess the intrarater reliability of measurement of pelvic and lower limb kinematics during two single leg landing tasks using 3D motion analysis.

Material and methods: 19 healthy volunteers (8 women, 11 men, age 23.1 ± 2.8 years, weight 70.7 ± 9.2 kg, height 174.8 ± 6.7 cm) performed five repeated single leg hurdle hops (SLHH) (30 cm height) and five single leg drop landings (SLDL) from a box (40 cm height) in one measurement session with a 15-minute break and after marker replacement with 3D assessment. The intraclass correlation coefficient (ICC), standard error of measurement (SEM), and the smallest detectable differences (SDD) were used to examine the reliability of kinematic parameters during the landing phase.

Results: The average intrarater ICC for SLHH was 0.92 (SEM = 1.69°, SDD 4.68°) and for SLDL was 0.96 (SEM = 0.81°, SDD = 2.26°). After marker replacement ICC decreased to an average value of 0.81 (SEM = 2.05°, SDD 5.68°) for SLHH and 0.82 (SEM = 2.36°, SDD 6.53°) for SLDL.

Conclusions: Using the 3D method to evaluate pelvis and lower limb kinematics during single leg landing in one measurement session is a high reliability method for most parameters. Marker replacement is one of the factors that reduce the reliability of measures. When applying the SEM and SDD values, which the present paper contains, it is worth mentioning that the obtained results are caused by measurement error or they are due to individual issues.

Influence of Anticipation and Motor-Motor Task Performance on Cutting Biomechanics in Healthy Men

CONTEXT

Biomechanical analyses of cutting tasks have demonstrated kinematic differences associated with the noncontact knee-injury risk when the movement direction is unanticipated. Motor-motor dual tasks occur within dynamic environments and change the demand for attentional resources needed to complete athletic maneuvers, which may contribute to injury risk.

OBJECTIVE

To investigate the influence of anticipation and motor-motor task performance on cutting biomechanics.

DESIGN

Cross-sectional study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 32 healthy, recreationally active men (age = 23.1 ± 3.6 years, height = 180.0 ± 7.0 cm, mass = 81.3 ± 17.3 kg) who self-reported regular participation in cutting sports.

INTERVENTION(S)

Participants performed a 45° side-step cut on the dominant limb in a random order of conditions: anticipation (anticipated, unanticipated) and task (no ball throw, ball fake, ball throw).

MAIN OUTCOME MEASURE(S)

Triplanar trunk, hip, and knee angles were assessed throughout the stance phase using 3-dimensional motion capture. Data were analyzed using a time series of means calculated from initial contact to toe-off (0%-100%) with 90% confidence intervals. Mean differences between conditions were identified as regions of nonoverlapping confidence intervals, and those that occurred during the region of peak vertical ground reaction force (0%-25%) are presented.

RESULTS

Regardless of anticipation, attending to a ball (ball throw) resulted in more trunk extension (range = 2.9°-3.7°) and less lateral trunk flexion toward the cutting direction (range = 5.2°-5.9°). Planning to attend to a ball (ball fake) resulted in less lateral trunk flexion toward the cutting direction (4.7°). During unanticipated cutting, more trunk rotation away from the cutting direction was observed when attending to a ball (range = 5.3°-7.1°). The interaction of anticipation and task had a similar influence on sagittal- and frontal-plane trunk position.

CONCLUSIONS

Motor-motor task performance and its interaction with anticipation induced an upright, neutral trunk position during side-step cutting, which has been associated with the risk for noncontact knee injury. Promoting task complexity during rehabilitation and injury-prevention programs may better prepare individuals to succeed when performing high-risk athletic maneuvers.

EFFECTS OF SURFACE ON TRIPLE HOP DISTANCE AND KINEMATICS

Background

The single leg triple hop (SLTH) test is often utilized by rehabilitation practitioners as a functional performance measure in a variety of patient groups. Accuracy and consistency are important when measuring the patient progress and recovery. Administering the SLTH test on different surfaces, consistent with the patient's sport, may affect the hop distances and movement biomechanics.

Purpose

The purpose of this study was to examine the effects of court and turf surfaces on the hop distance, limb symmetry index (LSI), and lower extremity kinematics of a SLTH test.

Methods

Recreationally active female participants (n=11, height 163.8 ± 7.1cm, mass 63.1 ± 7.1kg, age 18.9 ± 0.9yrs), without injury, volunteered to participate in the study. Three maximal effort SLTH test trials on two different surfaces (court, synthetic turf) were collected and analyzed using 3D motion analysis techniques. Outcome variables included SLTH test distances and LSI values and sagittal plane kinematics including trunk, hip, knee and ankle range of motion (ROM) during the last two landings of each SLTH test trial. The second landing involves an absorption phase and propulsion phase in contrast to the final landing which involves absorption and final balance on the single leg. Paired t-tests were used to determine differences between surfaces in hop distance and LSI values. Two-way repeated measures ANOVA were used to determine differences between surfaces in kinematic variables.

Results

The total SLTH test distance was not statistically different between the court (4.11 ± 0.47m) and turf (4.03 ± 0.42m, p=0.47) surfaces. LSI for the court surface was 100.8 ± 3.0% compared to 99.7 ± 3.0% for turf surface, which was not statistically different (p=0.30). Knee flexion ROM was significantly less (p=0.04) on the turf compared to the court surface during the second landing. Ankle flexion range of motion was also significantly less (p=0.03) during the second landing on turf compared to court.

Conclusions

Type of surface influenced landing kinematics but not total SLTH test distance. When evaluating the quality of landings during a SLTH test, it may be warranted to observe each type of landing and the type of surface used during single leg tests.

Level of Evidence

2.

A model-based approach to predict neuromuscular control patterns that minimize ACL forces during jump landing

Jump landing is a common situation leading to knee injuries involving the anterior cruciate ligament (ACL) in sports. Although neuromuscular control is considered as a key injury risk factor, there is a lack of knowledge regarding optimum control strategies that reduce ACL forces during jump landing. In the present study, a musculoskeletal model-based computational approach is presented that allows identifying neuromuscular control patterns that minimize ACL forces during jump landing. The approach is demonstrated for a jump landing maneuver in downhill skiing, which is one out of three main injury mechanisms in competitive skiing.

Muscle contributions to maximal single-leg forward braking and backward acceleration in elite athletes

Abrupt deceleration is a common practice in several sports, where sudden changes of direction are needed to reach the highest performance level. When inappropriately performed, these actions can impose excessive mechanical loads at the lower limb joints, specifically at the knee and ankle joints, usually associated with increased risk of injury. This work aims to estimate muscle forces and muscle contributions to the acceleration of the center of mass during a rapid maximal single-leg forward braking and backward acceleration task. Fourteen elite male injury-free indoor-sports athletes participated in this work. Scaled generic musculoskeletal models, consisting of 12 segments, 23 degrees of freedom, and 92 muscle-tendon actuators were used in OpenSim software. Due to the nature of the musculoskeletal system, all muscles are considered when joint and segment positions, velocities, and accelerations are calculated, resulting in muscles acting to accelerate joints it does not span. The knowledge of muscle interaction during this multijoint task is important and was achieved through an induced acceleration analysis. The vasti (-9.18 ± 2.09 and -7.63 ± 1.33 N/Kg) were the main contributors to the centre of mass deceleration profile along the anterior/posterior direction, aided by the soleus muscle (9.72 ± 2.35 and 9.62 ± 2.07 N/Kg), which counteracted most of the effects applied by gravity along the vertical direction, during both phases. This study provides a computational approach to quantify the dynamical interactions between muscles and joints during an abrupt anterior/posterior deceleration task, thus giving robust and insightful indicators that can be implemented in injury prevention protocols.

Timing of Muscle Activation Is Altered During Single-Leg Landing Tasks After Anterior Cruciate Ligament Reconstruction at the Time of Return to Sport

OBJECTIVES

It is well known that alterations in landing mechanics persist for years after anterior cruciate ligament reconstruction (ACL-R). Nevertheless, existing literature is controversial in reporting successful or unsuccessful recovery of prelanding muscle activation timing after ACL-R. The study aimed at comparing myoelectric and kinematic patterns during landing tasks between ACL-R and healthy subjects.

DESIGN

Cross-sectional study.

SETTING

Institutional research laboratory.

PATIENTS AND INTERVENTION

Fifteen male athletes after ACL-R using patellar tendon and 11 using hamstrings autograft at the time of return to sport were recruited. Fifteen healthy athletes served as control group. Participants performed 4 different single-leg landing tasks arriving onto a force plate.

MAIN OUTCOME MEASURES

Electromyographic (EMG) activity of knee extensors and flexors, normalized vertical ground reaction force (vGRF), and knee angular displacement were recorded.

RESULTS

In all the tasks, preimpact EMG duration was longer in ACL-R (112 ± 28 ms in the knee extensors; 200 ± 34 ms in the knee flexors) compared with healthy participants (74 ± 19 ms in the knee extensors; 153 ± 29 ms in the knee flexors; P < 0.05). Initial contact (IC) and maximum postimpact knee angle were lower in ACL-R (9 ± 7 degrees at IC; 39 ± 12 degrees at maximum flexion) compared with healthy participants (17 ± 9 degrees at IC; 52 ± 15 degrees at maximum flexion; P < 0.05). Normalized vGRF was higher in ACL-R compared with healthy participants (3.4 ± 0.5 and 2.7 ± 0.6; P < 0.05).

CONCLUSIONS

At the time of return to sport, ACL-R subjects showed altered motor control strategies of single-leg landings. These alterations may lead to uncoordinated movement, hence increasing the risk of reinjury.