3-Dimensional Biomechanics of Noncontact Anterior Cruciate Ligament Injuries in Male Professional Soccer Players.

BACKGROUND: The understanding of noncontact anterior cruciate ligament (ACL) injury causation in soccer has improved over the past decades. Bidimensional video analyses have significantly augmented our awareness, representing to date the only practical method to describe injury biomechanics. However, the extent of the problem continues to raise serious concerns. PURPOSE: To advance our understanding of the causal pathways leading to ACL injury with a large-scale reconstruction of 3-dimensional (3D) whole-body joint kinematics of injuries that occurred to male elite soccer players, as well as to compare the joint angle time course among situational patterns. STUDY DESIGN: Descriptive laboratory study. METHODS: A total of 33 consecutive noncontact and indirect contact ACL injuries that occurred in 6 national and 2 international professional leagues (seasons 2020-2021 to 2022-2023 until December 2022) were analyzed: (1) multiview noncoaxial television images were inspected; (2) multiple camera views were taken from 400 ms before the initial ground contact to 200 ms after the injury frame; (3) a size-matched pitch was modeled and used to calibrate cameras; (4) a 3D skeletal model was adjusted to fit the player's pose in each frame/view; and (5) poses were interpolated, and Euler joint angles were extracted. RESULTS: The authors reconstructed the 3D lower limb joint kinematic curves preceding and during ACL injuries in 33 cases; notably, a sudden external (up to 5°) and then internal knee rotation was observed after the initial contact and before the injury frame. The overall kinematics at injury were knee moderately flexed (45.9°± 21.7°), abducted (4.3°± 5.1°), and externally rotated (3.0°± 6.4°); trunk shallowly flexed (17.4°± 12.5°) and rotated and tilted toward the injured side; and hip flexed (32.0°± 18.7°), abducted (31.1°± 12.0°), and slightly internally rotated (6.6°± 12.2°). Variable behaviors were observed at the ankle level. CONCLUSION: Via reconstruction of the sequence of whole-body joint motion leading to injury, we confirmed the accepted gross biomechanics (dynamic valgus trend). This study significantly enriches the current knowledge on multiplanar kinematic features (transverse and coronal plane rotations). Furthermore, it was shown that ACL injuries in male professional soccer players manifest through distinct biomechanical footprints related to the concurrent game situation. CLINICAL RELEVANCE: Interventions aimed at reducing ACL injuries in soccer should consider that environmental features (ie, situational patterns) affect injury mechanics.

Kinematics of 90° change of direction in young football players: Insights for ACL injury prevention from the CUTtheACL study on 6008 trials.

PURPOSE: To investigate the 90° change of direction (COD) task in an extensive cohort of competitive healthy football players within the CUTtheACL study and to provide normative values and differences between males and females for full-body kinematics based on two-dimensional (2D) video analysis and scoring system. METHODS: One-thousand-and-two competitive football (soccer) players (age 16.3 ± 2.8 years, 264 females) were prospectively enroled. Each player performed three preplanned 90° COD tasks per limb. The 2D evaluation was performed through objective measures (collected through three high-speed cameras) of frontal and sagittal plane joint kinematics at the cut initial foot contact (IC) and maximum knee flexion angle. A previously published scoring system was adopted to measure the movement quality of the COD task. The scoring system included five criteria (limb stability [LS], pelvis stability [PS], trunk stability [TS], shock absorption [SA], movement strategy [MS]) ranked from 0/2 (nonadequate) to 2/2 (adequate) with a maximum score of 10/10. Normative data were provided for all the variables; statistical differences between male and female players were investigated (p < 0.05). RESULTS: A total of 6008 valid attempts were included. Frontal plane knee projection angle (FPKPA) at initial contact was 24.4 ± 9.8° (95th percentile: FPKPA > 40°). The total score was ≤4/10 in 71.2% of the trials, the lowest subscores were LS and PS. Female players showed different movement patterns with lower hip and trunk flexion both at IC and maximum knee flexion angle (p < 0.01, ES = 0.41-0.64). Female players also showed worse scores than males in SA, MS and total score (p < 0.01). CONCLUSION: Female players seem more prone to stiffer lower limb strategy and greater pelvis-trunk frontal plane instability than males. Clinicians could adopt normative data and sex-specific differences in players' movement techniques to improve ACL injury risk mitigation protocols. LEVEL OF EVIDENCE: Level IV.

Video Analysis of Anterior Cruciate Ligament Injuries in Male Professional Basketball Players: Injury Mechanisms, Situational Patterns, and Biomechanics.

Background: Improving our understanding of the situations and biomechanics that result in an anterior cruciate ligament (ACL) injury in basketball players may support the design of more effective programs to mitigate the risk of injury. Purpose: To (1) describe the mechanisms, situational patterns, and gross biomechanics (kinematics) of ACL injuries in professional basketball matches using video analysis and (2) document the distribution of ACL injuries according to player position, phase of the match, and location on the court. Study Design: Case series; Level of evidence, 4. Methods: A total of 38 ACL injuries in professional male European basketball leagues from the 2013-2014 to 2019-2020 seasons were identified. There were 36 (95%) injury videos analyzed for injury mechanisms and situational patterns, while biomechanical analysis was possible in 32 cases. Overall, 3 independent reviewers evaluated each video. Data according to player position (n = 38), phase of the match (n = 38), and location on the court (n = 36) were evaluated. Results: More injuries occurred while attacking (n = 25 [69%]) than defending (n = 11 [31%]). There was 1 (3%) direct contact injury, 21 (58%) indirect contact injuries, and 14 (39%) noncontact injuries. Most injuries (83%) occurred during 3 main situations: offensive cut (n = 17 [47%]), landing from a jump (n = 8 [22%]), and defensive cut (n = 5 [14%]). Injuries generally involved knee flexion (with minimal hip/trunk flexion and reduced plantarflexion) in the sagittal plane and knee valgus loading in most cases (75%). A similar number of injuries occurred during the first (53%) and second (47%) halves of the match, with a higher prevalence in the second (37%) and fourth (34%) quarters. Half of the injuries occurred during the first 10 minutes of effective playing time. More injuries occurred in guards (58%), and 73% of all injuries occurred in the scoring zone. Conclusion: Indirect contact was the main injury mechanism found in male professional basketball players. The offensive cut was the most common situational pattern. Biomechanical analysis confirmed a multiplanar mechanism, with knee loading in the sagittal plane accompanied by dynamic valgus. More injuries occurred in the first 10 minutes of a player's effective playing time, within the scoring zone, and among guards.

A comprehensive two-dimensional scoring system to assess the single-leg squat task in football players.

BACKGROUND: The single-leg squat (SLS) is a safe and widespread functional test commonly performed in the mid-stages of rehabilitation after severe knee injuries. The use of reliable objective measures has been advocated to improve the quality of SLS assessment. The aim of this study was to describe a qualitative whole-body scoring system based on two-dimensional (2D) video analysis during SLS test and validate it against three-dimensional (3D) kinetics and kinematics. METHODS: Thirty-four competitive football (soccer) players performed a series of SLS tasks. 3D kinematics and kinetics were collected through infrared cameras, and 2D video analysis was performed through a scoring system with sub-scores ranging from 0/2 (non-adequate movement) to 2/2 (adequate movement) based on frontal and lateral planes objective measurements. 3D kinematics and kinetics were grouped according to the results of the 2D evaluation and compared through the analysis of variance (P < 0.05). RESULTS: Higher hip adduction, hip internalrotation, and knee valgus collapse were found in trials rated 0/2 or 1/2 compared with theone rated 2/2 in the limb stability score. Hip flexion and hip/knee moment ratio were lower in those scoring 0/2 comparedwith those scoring 2/2 in the movement strategy criterion. A low total score was associated with higherknee valgus collapse and lower hip/knee extensor moment ratio. Compensatory strategieswere found in frontal plane scores. CONCLUSIONS: The 2D scoring system described was strongly associated with kinematics and kinetics from gold-standard 3D motion capture and might represent a valid tool to describe the movement quality of an SLS task.

No Association Between Hamstrings-to-Quadriceps Strength Ratio and Second ACL Injuries After Accounting for Prognostic Factors: A Cohort Study of 574 Patients After ACL-Reconstruction.

BACKGROUND: The stress on the anterior cruciate ligament (ACL) induced by the quadriceps can be attenuated by activation of the hamstrings by exerting an opposing torque to the anterior translation of tibia. Consequently, considering the ratio between strength of the hamstrings-to-quadriceps (HQ-ratio) may be of value to reduce the odds of second ACL injuries. The objective was therefore to evaluate (1) the association between HQ-ratio and the occurrence of a second ACL injury in patients after ACL-reconstruction within 2 years of return to preinjury sport level and (2) to compare the HQ-ratio between males and females after ACL reconstruction. METHODS: Patients who had undergone primary ACL reconstruction and participated in knee-strenuous activity preinjury were included. Demographics, the occurrence of a second ACL injury, and muscle strength test results before returning to preinjury sport level were extracted from a rehabilitation registry. The endpoint was set at a second ACL injury or 2 years after return to preinjury sport level. A multivariable logistic regression was used to analyze the association between the HQ-ratio and a second ACL injury. RESULTS: A total of 574 patients (50.0% female) with a mean age of 24.0 ± 9.4 years at primary ACL reconstruction were included. In the univariable logistic regression analysis, the odds of sustaining a second ACL injury decreased by 3% for every 1% increase in the HQ-ratio (OR 0.97 [95% CI 0.95-1.00], p = 0.025). After adjusting for the time from reconstruction to return to preinjury sport level, sex, preinjury sport level, graft choice, age, and body mass index, the results were no longer significant (OR 0.98 [95% CI 0.95-1.01], p = 0.16). Females had a higher HQ-ratio compared with males for both the ACL-reconstructed and uninjured side (3.7% [95% CI 5.7; 1.8%], p = 0.0002 and 3.3% [95% CI 4.6; 2.1], p < 0.001, respectively). CONCLUSION: The HQ-ratio did not significantly affect the odds for sustaining a second ACL injury upon return to preinjury sports level after primary ACL reconstruction. Females had a significant higher HQ-ratio than males for both the ACL reconstructed and uninjured side.

Neurocognitive Errors and Noncontact Anterior Cruciate Ligament Injuries in Professional Male Soccer Players.

CONTEXT: Evidence is emerging that core neurocognitive functions such as working memory and inhibitory control (ie, motor-response and attentional inhibition) are linked to the anterior cruciate ligament (ACL) injury risk. Research has been conducted in laboratory settings, but the contribution of neurocognition to actual ACL injuries under real-world conditions is unknown. OBJECTIVE: To describe the possible neurocognitive errors involved in noncontact ACL injury mechanisms. DESIGN: Case series. SETTING: Soccer matches. PATIENTS OR OTHER PARTICIPANTS: A total of 47 professional male soccer players. MAIN OUTCOME MEASURE(S): Three independent reviewers evaluated 47 videos of players sustaining noncontact ACL injuries. Neurocognitive errors in inhibitory control were operationalized as follows: (1) motor-response inhibition was scored when a player demonstrated poor decision-making and approached the opponent with high speed that reduced the ability to stop or change the intended action and (2) an attentional error was scored when a player shifted his selective attention away from the relevant task to irrelevant stimuli. RESULTS: Of 47 noncontact ACL injuries, 26 (55%) were related to a pressing-type injury, 19 (73%) of which involved a deceiving action made by the opponent, suggesting poor inhibitory control of the defender. Of the remaining 21 noncontact ACL injuries (45%), 16 (76%) could be attributed to attentional errors. Agreement among the 3 raters was very good for all items except poor decision-making, which showed fair to good agreement (Fleiss κ = 0.71). Interrater reliability was excellent (intraclass correlation coefficient = 0.99-1.00). CONCLUSIONS: Errors in motor-response inhibitory control and attentional inhibition were common during noncontact ACL injury events in professional male soccer players. The interrater agreement in detecting neurocognitive errors in general was very good.

Optimising the Early-Stage Rehabilitation Process Post-ACL Reconstruction.

Outcomes following anterior cruciate ligament reconstruction (ACLR) need improving, with poor return-to-sport rates and a high risk of secondary re-injury. There is a need to improve rehabilitation strategies post-ACLR, if we can support enhanced patient outcomes. This paper discusses how to optimise the early-stage rehabilitation process post-ACLR. Early-stage rehabilitation is the vital foundation on which successful rehabilitation post-ACLR can occur. Without high-quality early-stage (and pre-operative) rehabilitation, patients often do not overcome major aspects of dysfunction, which limits knee function and the ability to transition through subsequent stages of rehabilitation optimally. We highlight six main dimensions during the early stage: (1) pain and swelling; (2) knee joint range of motion; (3) arthrogenic muscle inhibition and muscle strength; (4) movement quality/neuromuscular control during activities of daily living (5) psycho-social-cultural and environmental factors and (6) physical fitness preservation. The six do not share equal importance and the extent of time commitment devoted to each will depend on the individual patient. The paper provides recommendations on how to implement these into practice, discussing training planning and programming, and suggests specific screening to monitor work and when the athlete can progress to the next stage (e.g. mid-stage rehabilitation entry criteria).

Better Safe Than Sorry? A Systematic Review with Meta-analysis on Time to Return to Sport After ACL Reconstruction as a Risk Factor for Second ACL Injury.

OBJECTIVE: To compare the time to return to sport (RTS) between patients who did and did not suffer a second anterior cruciate ligament (ACL) injury after ACL reconstruction. DESIGN: Etiology systematic review with meta-analysis. LITERATURE SEARCH: Cochrane Library, Embase, Medline, AMED, and PEDro databases were searched in August 2021 and again in November 2022. STUDY SELECTION CRITERIA: Clinical studies reporting time to RTS after ACL reconstruction and second ACL injury were eligible. DATA SYNTHESIS: We pooled continuous data (time [months] and proportions [%]), with random-effects meta-analyses. Pooled estimates were summarized in forest plots. A qualitative data synthesis was also performed. RESULTS: Twenty-one studies were included in the meta-analysis and 33 in the qualitative synthesis. Pooled incidence of second ACL injury was 16.9% (95% confidence interval [CI]: 12.8, 21.6). Patients who suffered a second ACL injury returned to sport significantly earlier (25 days; 95% CI: 9.5, 40.4) than those who did not suffer another injury. There was no difference in time to RTS for professional athletes who suffered a second ACL injury and those who did not. The certainty of evidence was very low. CONCLUSION: There was very low-certainty evidence that patients who suffered a second ACL injury had returned to sport 25 days earlier than patients who did not have another injury. For professional athletes, there was no difference in time to RTS between athletes who suffered a second ACL injury and athletes who did not. J Orthop Sports Phys Ther 2024;54(3):1-15. Epub 30 November 2023. doi:10.2519/jospt.2023.11977.

Injury mechanisms and situational patterns of severe lower limb muscle injuries in male professional football (soccer) players: a systematic video analysis study on 103 cases.

OBJECTIVE: The objective of this study is to describe the mechanism of injury and situational patterns (based on ball possession and playing action leading to injury) of severe (lay-off time >28 days) lower limb muscle injuries in professional male football (soccer) players during match play. METHODS: Players experiencing a severe muscle injury of the lower limb during Italian first (Serie A) division male football matches over three consecutive seasons (2018-2021) were identified. Video footage was obtained and three raters independently categorised injury mechanism and situational patterns using a standardised checklist. Injury epidemiology (month), timing of injuries within the match and location of injuries on the pitch were also examined. RESULTS: We identified 121 lower limb severe muscle injuries. Videos of sufficient quality were available for 103 (85%) cases, including 61 (60%) hamstring, 17 (16%) calf, 16 (15%) adductor and 9 (9%) quadricep muscle injuries. Nearly two-thirds of injuries involved the dominant/kicking leg (n=65, 63%). Eighty-five (83%) injuries were non-contact and 18 (17%) indirect contact. Four main situational patterns were identified and accounted for 88% of injuries: (1) running/acceleration (n=35, 34%); (2) closed kinetic chain stretching (n=21, 20%); (3) open kinetic chain stretching (n=19, 18%) and (4) kicking (n=16, 16%), with differences between muscle groups. 71% of injuries occurred in the first half of the match (p<0.01), with a gradual increase through the first half. CONCLUSION: Most severe muscle injuries during football matches were non-contact and occurred in the first half during running/acceleration, open and closed kinetic chain stretching, or kicking.

Two-Dimensional and Three-Dimensional Biomechanical Factors During 90° Change of Direction are Associated to Non-Contact ACL injury in Female Soccer Players.

Background: The two-dimensional (2D) video-analysis of the change of direction (COD) technique has never been used to attempt to predict the risk of ACL injury in female football players. Hypothesis/Purpose: The purpose of the present pilot study was to prospectively investigate the biomechanical predictors of ACL injury during a COD task in female football players using both gold standard 3D motion capture and a qualitative scoring system based on 2D video-analysis. Study Design: Prospective cohort study. Methods: Sixteen competitive female football (soccer) players (age 21.4 ± 4.3) performed a series of pre-planned 90° COD tasks. 3D motion data was recorded through 10 stereophotogrammetric cameras and a force platform. 2D frontal and transverse plane joint kinematics were computed through video-analysis from three high-speed cameras. A scoring system based on five criteria was adopted: limb stability, pelvis stability, trunk stability, shock absorption, and movement strategy. The players were prospectively followed for the next two consecutive football seasons and the occurrence of severe knee injuries was registered. Results: Four players (25%) experienced an ACL injury. In 3D analysis, ACL-injured players showed greater knee valgus, knee internal rotation, and lower knee flexion (p= 0.017 - 0.029). Lower hip flexion coupled with greater external rotation (p= 0.003 - 0.042), ankle eversion, and contralateral pelvic drop (p<0.001) were also noted. In 2D analysis, ACL-injured players showed greater internal foot rotation, contralateral pelvic drop, lower knee flexion, and contralateral trunk tilt (moderate-to-large effect size). Pelvis stability and trunk stability showed the highest predictive value towards ACL injury. Total score was significantly lower in ACL-injured players with a moderate effect size (d=0.45). Conclusions: Both 3D and 2D methodologies depicted biomechanical risk factors and offered predictive insights towards the ACL injury risk. Awareness should rise in women's football regarding the high risk of ACL injury and the strategies to assess and mitigate it. Level of Evidence: 3©The Author(s).

Foot rotation and pelvic angle correlate with knee abduction moment during 180° lateral cut in football players.

BACKGROUND: Lateral movements are challenging for 2D video-analysis and are therefore often omitted in functional tests for Anterior Cruciate Ligament (ACL) injury risk assessment. The purpose of the present study was to investigate the association between frontal and transverse plane angles obtained from 2D video-analysis and knee abduction moment (KAM) from gold standard 3D motion capture in a 180° lateral cut task. The hypothesis was that 2D angles other than the knee joint effectively explain variations in KAM. METHODS: Thirty-four healthy football players (age 22.8 ± 4.1 years) performed a series of 180° lateral cut (lateral shuffles) tasks. The peak KAM was collected through a 3D motion capture system. A 2D video-analysis movement assessment identified frontal and transverse plane joint kinematics: foot projection angle (FPA), Frontal Plane Knee Projection Angle (FPKPA), Pelvis tilt angle (PA), and Trunk tilt angle (TA). A forward stepwise regression model was used to assess significant 2D predictors of KAM (p < 0.05). RESULTS: FPA and PA were the only significant predictors (R2-ajdusted = 9.2%, p < 0.001), with external foot rotation and contralateral pelvic drop associated with higher KAM. Based on the regression model, the "High FPA & PA group" was defined and showed higher KAM than the rest of the cohort (p = 0.012, ES = 0.71). CONCLUSIONS: The external foot rotation and the contralateral pelvic drop from 2D video-analysis were associated with higher peak KAM during the 180° lateral cut. A qualitative assessment of the 180° lateral cut could offer precious insights on ACL injury risk mitigation. LEVEL OF EVIDENCE: Descriptive Laboratory Study.

Knee Joint Contact Forces during High-Risk Dynamic Tasks: 90° Change of Direction and Deceleration Movements.

Pivoting sports expose athletes to a high risk of knee injuries, mainly due to mechanical overloading of the joint which shatters overall tissue integrity. The present study explored the magnitude of tibiofemoral contact forces (TFCF) in high-risk dynamic tasks. A novel musculoskeletal model with modifiable frontal plane knee alignment was developed to estimate the total, medial, and lateral TFCF developed during vigorous activities. Thirty-one competitive soccer players performing deceleration and 90° sidestepping tasks were assessed via 3D motion analysis by using a marker-based optoelectronic system and TFCF were assessed via OpenSim software. Statistical parametric mapping was used to investigate the effect of frontal plane alignment, compartment laterality, and varus-valgus genu on TFCF. Further, in consideration of specific risk factors, sex influence was also assessed. A strong correlation (R = 0.71 ÷ 0.98, p < 0.001) was found between modification of compartmental forces and changes in frontal plane alignment. Medial and lateral TFCF were similar throughout most of the tasks with the exception of the initial phase, where the lateral compartment had to withstand to higher loadings (1.5 ÷ 3 BW higher, p = 0.010). Significant sex differences emerged in the late phase of the deceleration task. A comprehensive view of factors influencing the mediolateral distribution of TFCF would benefit knee injury prevention and rehabilitation in sport activities.

Football-specific extension of the IOC consensus statement: methods for recording and reporting of epidemiological data on injury and illness in sport 2020.

Several sports have published consensus statements on methods and reporting of epidemiological studies concerning injuries and illnesses with football (soccer) producing one of the first guidelines. This football-specific consensus statement was published in 2006 and required an update to align with scientific developments in the field. The International Olympic Committee (IOC) recently released a sports-generic consensus statement outlining methods for recording and reporting epidemiological data on injury and illness in sport and encouraged the development of sport-specific extensions.The Fédération Internationale de Football Association Medical Scientific Advisory Board established a panel of 16 football medicine and/or science experts, two players and one coach. With a foundation in the IOC consensus statement, the panel performed literature reviews on each included subtopic and performed two rounds of voting prior to and during a 2-day consensus meeting. The panel agreed on 40 of 75 pre-meeting and 21 of 44 meeting voting statements, respectively. The methodology and definitions presented in this comprehensive football-specific extension should ensure more consistent study designs, data collection procedures and use of nomenclature in future epidemiological studies of football injuries and illnesses regardless of setting. It should facilitate comparisons across studies and pooling of data.

Video analysis of Achilles tendon rupture in male professional football (soccer) players: injury mechanisms, patterns and biomechanics.

Background: Achilles tendon rupture (ATR), while rare in football, is a severe career-threatening injury associated with long-layoff times. To date, no study has documented ATR's mechanism in professional football players. Aim: To describe the mechanisms, situational patterns and gross biomechanics (kinematics) of ATR injuries in professional male football players. Methods: Eighty-six (n=86) consecutive ATR injuries in professional football players during official matches were identified. Sixty (70%) injury videos were identified for mechanism and situational pattern, with biomechanical analysis feasible in 42 cases. Three independent reviewers evaluated the injury videos. Distribution of ATR during the season, the match play and on the field were also reported. Results: Fifty (n=50, 83%) injuries were classified as non-contact and 10 (17%) as indirect contact. ATRs are injuries occurring during accelerations; three main situational patterns were identified: (1) forward acceleration from standing (n=25, 42%); (2) cross-over cutting (n=15, 25%) and (3) vertical jumping (n=11, 18%). Biomechanically, ATR injuries were consistent with a multiplanar loading at the injury frame consisting of a slightly flexed trunk (15.5°), extended hip (-19.5°), early flexed knee (22.5°) and end-range dorsiflexed (40°) ankle in the sagittal plane and foot pronation; 27 (45%) ATRs occurred in the first 30 min of effective match time. Conclusions: All ATRs in professional football were either non-contact (83%) or indirect contact (17%) injuries. The most common situational patterns were forward acceleration from standing, cross-over cutting and vertical jumping. Biomechanics was consistent and probably triggered by a multiplanar, although predominantly sagittal, loading of the injured Achilles tendon.

The three-dimensional reconstruction of an Achilles tendon rupture in a professional football player reveals a multiplanar injury mechanism.

Achilles tendon rupture (ATR) is a rare although very serious injury for football players; currently, studies on ATR in football are scant. This case report intends to firstly describe the situational pattern and three-dimensional mechanism of the ATR injury occurred to a professional football player during the last UEFA 2020 Championship. To reconstruct the full 3D joint kinematics throughout the injury action, the model-based image-matching technique was used. The key findings were: (i) ATR injury combined a sudden ankle dorsiflexion action with an internal plantarflexion moment while performing a crossover cut at high speed; (ii) a multi-planar loading occurred during the push-off phase.Level of evidence V.

Do healthy athletes exhibit at-risk biomechanics for anterior cruciate ligament injury during pivoting movements?

A consistent injury mechanism involving multiple joints has been highlighted in athletes experiencing anterior cruciate ligament (ACL) rupture. However, if and to what extent healthy athletes incur an unsafe biomechanical profile during high-dynamics movements is unknown. The present study aimed to investigate the occurrence of the ACL risk profile in a competitive pivoting sports population.Thirty-four athletes (22.8 ± 4.1 y) performed a frontal deceleration and a change of direction at 90°. Full-body kinematics was collected through 15 wearable inertial sensors (Awinda, Xsens). Nine ACL risk factors were defined based on four categories: limited lower limb flexion, valgus collapse, foot rotation and trunk rotation. A movement trial was considered 'at-risk' in the presence of at least 5 simultaneous risk factors. The rate of athletes with at-risk movements was assessed and multivariate regression for associated outcomes was conducted.The overall rate of injury profile occurrence was 9-12%. The injury profile was identified at least in one trial in 24 athletes (71%) and three trials in 5 athletes (15%). Significant associations were found for higher approaching speed (OR = 4.3) and female sex (OR = 4.8). A large occurrence of the typical ACL injury biomechanical profile was noticed. Large screenings are advisable to identify at-risk athletes and promote preventative strategies.

Beyond Distance: A Simple Qualitative Assessment of the Single-Leg Hop Test in Return-to-Play Testing.

BACKGROUND: Limb symmetry index in the single-leg hop (SLH) test has been questioned for its low predictive value in identifying secondary anterior cruciate ligament (ACL) injury. The purpose of this study was to describe a qualitative 2-dimensional (2D) scoring system for the assessment of the SLH test and associate it with the vertical ground-reaction forces (vGRF) and sagittal plane biomechanics evaluated through gold standard 3D motion analysis. HYPOTHESIS: Stiff landings would be associated with low 2D scores. STUDY DESIGN: Descriptive laboratory study. LEVEL OF EVIDENCE: Level 4. METHODS: Thirty-four competitive football (soccer) players (age 22.8 ± 4.1 years, 16 women) were enrolled. Each athlete performed a series of SLH tests. Three-dimensional motion analysis was recorded using 10 stereophotogrammetric cameras, a force platform, and 3 high-speed cameras. The 2D qualitative assessment was performed through a scoring system based on the video-analysis of sagittal plane joint kinematics. A score of 0/2 (inadequate), 1/2 (partially adequate), or 2/2 (adequate) was attributed to the movement, based on objective measurements. The vGRF was extracted from the force platform and grouped according to the results of the 2D evaluation. RESULTS: Significantly higher vGRF (stiffer landing) was found for athletes obtaining a 0/2 score compared with those obtaining a 2/2 score (up to 0.8 body weight higher, P < 0.01). A significant negative rank correlation was found between the vGRF and the total score (ρ = -0.17, P = 0.03). CONCLUSION: The qualitative scoring system effectively identified stiff landings in the SLH for distance test. CLINICAL RELEVANCE: The qualitative scoring system could be a user-friendly standardized method to assess athletes' movement quality in return to sport clearance decision after ACL injury.

Confidence to Return to Play After ACL Reconstruction: An Evaluation of Quadriceps Strength Symmetry and Injury Mechanism in Male Athletes.

BACKGROUND: After anterior cruciate ligament reconstruction (ACLR), diminished quadriceps strength symmetry and reduced psychological readiness to return to play (RTP) increase the risk for subsequent injury. Although the relationship between quadriceps strength symmetry and psychological readiness to RTP has been reported to be influenced by injury mechanism in female athletes, it is unclear whether such a relationship exists in male athletes. HYPOTHESIS: Quadriceps strength symmetry would be positively associated with greater psychological readiness to RTP after ACLR, regardless of injury mechanism. STUDY DESIGN: Retrospective cohort. LEVEL OF EVIDENCE: Level 3 (cohort study). METHODS: Sixty male patients completed strength testing and the Injury-Psychological Readiness to Return to Sport Scale (I-PRRS) at an outpatient clinical facility as part of return to sport testing after ACLR. Linear regression analysis was used to assess the relationship between the I-PRRS and the independent variables of interest (quadriceps strength symmetry and injury mechanism). RESULTS: For all patients combined, no symmetry × mechanism interaction was found (P = 0.11). A significant positive relationship was found between quadriceps strength symmetry and the I-PRRS score (P < 0.001, R2 = 0.31), after adjusting for time post-ACLR and injury mechanism. CONCLUSION: Greater quadriceps strength symmetry was associated with greater psychological readiness to RTP after ACLR in male athletes. In contrast to what has been reported in female athletes, this relationship was independent of injury mechanism. CLINICAL RELEVANCE: Given the potential negative consequences of quadriceps strength deficits on one's confidence to RTP, the need to restore quadriceps symmetry during the postoperative period is readily apparent. Low confidence or low psychological readiness to RTP may be indicative of quadriceps strength asymmetry or poor physical function in general.

A 2D video-analysis scoring system of 90° change of direction technique identifies football players with high knee abduction moment.

PURPOSE: Abnormal joint biomechanics and poor neuromuscular control are modifiable risk factors for Anterior Cruciate Ligament (ACL) injury. Although 3D motion capture is the gold standard for the biomechanical evaluation of high-speed multidirectional movements, 2D video analysis is a growing-interest alternative because of its higher cost-effectiveness and interpretability. The aim of the present study was to explore the possible association between a 2D evaluation of a 90° change of direction (COD) and the KAM measured with gold standard 3D motion analysis. METHODS: Thirty-four competitive football (soccer) players (age 22.8 ± 4.1, 18 male and 16 females) were enrolled. Each athlete performed a series of pre-planned 90° COD at the maximum speed possible in a laboratory equipped with artificial turf. 3D motion analysis was recorded using 10 stereophotogrammetric cameras, a force platform, and three high-speed cameras. The 2D evaluation was performed through a scoring system based on the video analysis of frontal and sagittal plane joint kinematics. Five scoring criteria were adopted: limb stability (LS), pelvis stability (PS), trunk stability (TS), shock absorption (SA), and movement strategy (MS). For each criterion, a sub-score of 0/2 (non-adequate), 1/2 (partially adequate), or 2/2 (adequate) was attributed to the movement, based on objective measurements. The intra-rater and inter-rater reliability were calculated for each criterion and the total score. The Knee Abduction Moment (KAM) was extracted from the 3D motion analysis and grouped according to the results of the 2D evaluation. RESULTS: Excellent intra-rater reliability (ICC > 0.88) and good-to-excellent inter-rater reliability (ICC 0.68-0.92) were found. Significantly higher KAM was found for athletes obtaining a 0/2 score compared to those obtaining a 2/2 score in all the sub-criteria and the total score (20-47% higher, p < 0.05). The total score and the LS score showed the best discriminative power between the three groups. CONCLUSION: The 2D video-analysis scoring system here described was a simple and effective tool to discriminate athletes with high and low KAM in the assessment of a 90° COD and could be a potential method to identify athletes at high risk of non-contact ACL injury. LEVEL OF EVIDENCE: IV.