Peak Knee Valgus Moment Research Articles

Dual tasking increases kinematic and kinetic risk factors of ACL injury

ABSTRACT ACL injuries are common among athletes playing team sports. The impact of divided attention during team sports on landing mechanics is unclear. Twenty-one healthy females jumped at a 60° angle to their right and performed a second jump to their right or left at a 60° angle. The direction of the second jump was shown before movement (baseline) or mid-flight of the first jump (dual task). The signal for the dual-task conditions showed five arrows and the middle one indicated the jump direction (Flanker paradigm). The other arrows pointed in the same (congruent) or the opposite (incongruent) direction as the middle arrow. Results indicated larger initial and peak knee flexion angles, smaller peak knee valgus moments, and smaller vertical and posterior GRFs during baseline right jumps compared to other conditions. Peak posterior GRF was increased in the incongruent condition compared to the congruent condition during left jumps. Performance was decreased with longer stance times for the dual task compared to the baseline in both jump directions. Further, the incongruent condition had a longer stance time than the congruent condition during left jumps. More research focusing on decision-making with more challenging visual stimuli mimicking dynamic team sports is merited.

The Association Between Functional Movement Screen Scores and Knee Valgus Moments During Unplanned Sidestep Cutting in Netball.

Regular employment of three-dimensional (3D) motion analyses to assess and monitor knee valgus moments; a contributor to non-contact anterior cruciate ligament (ACL) injury; during unplanned sidestep cutting (USC) is costly and time-consuming. An alternative quick-to-administer assessment tool to infer an athlete's risk for this injury could allow prompt and targeted interventions to mitigate this risk. This study investigated whether peak knee valgus moments (KVM) during weight-acceptance phase of an unplanned sidestep cut were correlated with composite and component scores of the Functional Movement Screen (FMS™). Cross-sectional, Correlation. Thirteen female national-level netballers performed six movements of the FMS™ protocol and three trials of USC. A 3D motion analysis system captured lower limb kinetics and kinematics of each participant's non-dominant leg during USC. Averages of peak KVM across USC trials were calculated and examined for correlations with composite and component scores of the FMS™. No correlations were found between FMS™ composite or any of its component scores with peak KVM during USC. The current FMS™ did not show any correlations with peak KVM during USC on the non-dominant leg. This suggests that the FMS™ has limited utility in screening for non-contact ACL injury risks during USC. 3.

Correlation of Lower Limb Muscle Activity with Knee Joint Kinematics and Kinetics during Badminton Landing Tasks

A study on a single-leg landing task after an overhead stroke in badminton suggests that poor knee biomechanical indicators may be a risk factor for anterior cruciate ligament (ACL) injury. A preventive program targeting neuromuscular control strategies is said to alter the biomechanics of the knee joint and have a beneficial effect on reducing ACL injury. However, the relationship between muscle activity around the knee joint and knee biomechanical risk factors in the badminton landing task is unclear. The purpose of this study was to investigate the relationship between this movement pattern of muscle activity and knee kinematics and kinetics. This experiment analyzed knee muscle activity and biomechanical information in a sample of 34 badminton players (17 male, 17 female) during a badminton landing task. We assessed the relationship between the rectus femoris (RF), medial hamstring (MHAM), lateral hamstring (LHAM), medial gastrocnemius (MGAS), lateral gastrocnemius (LGAS), medial and lateral hamstring to quadriceps co-contraction ratio (MH/Q and LH/Q) with the knee flexion angle, valgus angle, extension moment, valgus moment, and proximal tibial anterior shear force. A moderate negative correlation was found between the peak knee flexion angle and electromyography (EMG) activity in LGAS (r = 0.47, p = 0.0046, R2 = 0.23, 95% CI: 0.16 to 0.70). Peak proximal tibial shear force showed strong and positive correlations with RF EMG activity (r = 0.52, p = 0.0016, R2 = 0.27, 95% CI: 0.22 to 0.73) and strong and negative correlations with MH/Q (r = 0.50, p = 0.0023, R2 = 0.25, 95% CI: 0.20 to 0.72). The knee extension moment showed moderate and positive correlations with RF EMG activity (r = 0.48, p = 0.0042, R2 = 0.23, 95% CI: 0.17 to 0.70) and strong and negative correlations with MH/Q (r = 0.57, p = 0.0004, R2 = 0.33, 95% CI: 0.29 to 0.76). The peak knee valgus moment showed strong and positive correlations with LH/Q (r = 0.55, p = 0.0007, R2 = 0.31, 95% CI: 0.26 to 0.75). Our findings suggest that there is a correlation between lower extremity muscle activity and knee kinematics and kinetics during the single-leg landing task in badminton; therefore, lower extremity muscle activity should be considered when developing rehabilitation or injury prevention programs.

Sex difference in effect of ankle landing biomechanics in sagittal plane on knee valgus moment during single-leg landing

Ankle landing strategies affects the biomechanical characteristics of the knee joint, especially knee frontal plane loading. However, no studies have investigated whether the association between ankle landing biomechanics in sagittal plane and the knee frontal plane loading differs between sexes. The purpose of this study was to examine whether there is a sex difference in the effect of ankle plantar flexion at the contact angle, ankle range of motion (ROM), and ankle plantar flexion moment on knee valgus loading during single-leg landing. Twenty-five females and twenty-four males performed a single-leg landing. Joint kinematics and kinetics of the lower extremities were measured. The relationship between ankle biomechanics in the sagittal plane (ankle plantar flexion angle at contact, ROM, and peak ankle plantar flexion moment) and peak knee valgus moment were analyzed. In males, the larger ankle plantarflexion angle at contact and ROM were significantly associated with lower peak knee valgus moment. In addition, in males only, a greater peak ankle plantar flexion moment was significantly associated with a lower peak knee valgus moment and greater peak ankle inversion moment. Altering ankle landing strategies in the sagittal plane during single-leg landing may reduce the knee valgus moment, which is one of risk factors for anterior cruciate ligament injury, in males only.

Breast Support Alters Trunk And Knee Joint Biomechanics During Double Limb Landing

Female athletes have a greater prevalence of traumatic knee injury than male athletes. Sex-based differences in injury rates emerge with maturation and the development of sex-specific traits including breast development. Breast support is known to alter trunk biomechanics during running tasks while in landing trunk orientation has been shown to mediate ACL strain. However, the effect of breast support on knee joint biomechanics has not been previously investigated. PURPOSE: To examine the effects of breast support on trunk and knee joint biomechanics during double limb landing. METHODS: Fourteen female collegiate athletes performed five double-limb landing trials in each of three sports bra conditions: no support, low support, and high support. Three-dimensional kinematics (240 Hz, Qualisys) and ground reaction forces (1200 Hz, AMTI Inc.) were recorded simultaneously. Visual 3D (C-Motion Inc.) was used to calculate peak trunk segment angles as well as peak knee joint angles and extension moments. A repeated measures ANCOVA with post-hoc pairwise comparisons were used to evaluate the effect of breast support on knee biomechanics. RESULTS: Increasing levels of breast support were associated with reductions in peak knee flexion (p = 0.008), peak knee valgus angles (p = 0.011) and peak knee valgus moments (p = 0.033) while there were no changes in peak knee moments (p = 0.216). Trunk flexion at initial contact (p = 0.024) and peak trunk flexion (p = 0.002) increased in response to greater breast support. CONCLUSIONS: The current data revealed a multi-joint mechanical adaptation in response to lower levels of breast support. These altered biomechanical patterns are consistent with a greater risk of traumatic knee injury including ACL rupture.

Optical Microscope Rehabilitation Nursing Study of Anterior Cruciate Ligament Injury through Lateral Knee Incision Based on Medical Internet of Things.

With the high development of sports, football has attracted more and more attention from the public. However, the hot competition has made football players undergo high-intensity training, and the risk of injury caused by training is also increasing. Lateral incision knee ACL injury is one of the most common types of injuries in football players, which has a serious impact on the athlete's physiology and daily training. The comprehensive, multi-level, convenient and fast medical system brought by the medical Internet of Things has become the growing demand of the medical industry. Based on the medical Internet of Things, this paper studies the rehabilitation nursing of football players' ACL injury by lateral cutting and running combined with optical microscope. In this paper, 36 male and female football players were selected for group experiments, and the landing and peak torque indexes of the experimental group and the control group of male and female athletes were analyzed under the observation of an optical microscope. Group (P <0.05), coxa valgus (P <0.01), internal rotation and knee valgus angles were greater than those in the EM group. And the peak hip flexion angle and knee valgus moment in NF group were lower than those in EF group (P <0.05). After 12 weeks of rehabilitation training, there was a significant difference in the Q/H joint contraction index between the REF group and the CON group (P <0.05), and there was no statistical difference in the other groups. After 12 weeks of rehabilitation training, there was a significant difference in the Q/H joint contraction index between the REF group and the CON group (P <0.05), and there was no statistical difference in the other groups. That is to say, after the systematic rehabilitation training proposed in this paper, the joint contraction performance of the hamstrings/quadriceps in the REF group has been significantly improved. This shows that the rehabilitation nursing under the optical microscope based on the medical Internet of Things has a good effect on the rehabilitation of the football player's side-cut running knee joint ACL injury.

Don't Peak Too Early: Evidence for an ACL Injury Prevention Mechanism of the 11+ Program.

BackgroundThe 11+ program prevents anterior cruciate ligament (ACL) injuries in athletes through unknown mechanisms.PurposeThe aim of the current study was to evaluate the effects of The 11+ intervention program, performed by female soccer players during a single season, on the frequency of Early Peaks during athletic tasks.MethodsThree teams (69 players) of collegiate female soccer athletes (Divisions I and II) were recruited. Two teams (49 players) volunteered to perform The 11+ three times per week for one season (~22 weeks plus three weeks pre-season), and one team (20 players) served as controls. The athletes performed three repetitions of a cutting maneuver, side shuffle direction change, and forwards to backwards running direction change before and after the competitive season and were recorded using marker-based 3D motion capture. Knee valgus moment time series were calculated for each repetition with inverse kinematics and classified as either “Very Early Peak”, “Early Peak” or “other” using cluster analysis. The classification was based timing of the peak relative to the timing of ACL injuries. The effect of the intervention on the frequency of Very Early Peaks and Early Peaks was evaluated with a mixed Poisson regression controlling for the movement task and pre-season frequency.ResultsThe 11+ intervention reduced the frequency of Early Peak knee valgus moment in one intervention team (coefficient = -1.16, p = 0.004), but not the other (coefficient = -0.01, p = 0.977). No effect was observed on the frequency of Very Early Peak knee valgus moment.ConclusionsReduced frequency of knee valgus moment Early Peak during athletic tasks may explain the mechanism by which The 11+ program decreases risk of ACL injury. Prospective studies with a much larger sample size are required to establish a link between Early Peak knee valgus moments and risk of ACL injury.Level of evidence2b

Greater Breast Support Alters Trunk and Knee Joint Biomechanics Commonly Associated With Anterior Cruciate Ligament Injury.

ObjectiveThe female breast is a passive tissue with little intrinsic support. Therefore, women rely on external breast support (sports bras) to control breast motion during athletic tasks. Research has demonstrated that lower levels of breast support are associated with altered trunk and pelvis movement patterns during running, a common athletic task. However, no previous study has identified the effect of sports bra support on movement patterns during other athletic tasks including landing. Therefore, the purpose of this study was to examine the effects of breast support on trunk and knee joint biomechanics in female collegiate athletes during a double-leg landing task.MethodsFourteen female collegiate athletes completed five double-leg landing trials in each of three different sports bra conditions: no support, low support, and high support. A 10-camera motion capture system (250 Hz, Qualisys, Goteburg, Sweden) and two force platforms (1,250 Hz, AMTI, Watertown, MA, USA) were used to collect three-dimensional kinematics and ground reaction forces simultaneously. Visual 3D was used to calculate trunk segment and knee joint angles and moments. Custom software (MATLAB 2021a) was used to determine discrete values of dependent variables including vertical breast displacement, knee joint and trunk segment angles at initial contact and 100 ms post-initial contact, and peak knee joint moments. A repeated measures analysis of covariance with post-hoc paired samples t-tests were used to evaluate the effect of breast support on landing biomechanics.ResultsIncreasing levels of breast support were associated with reductions in peak knee flexion (Right: p = 0.008; Left: p = 0.029) and peak knee valgus angles (Right: p = 0.011; Left: p = 0.003) as well as reductions in peak knee valgus moments (Right: p = 0.033; Left: p = 0.013). There were no changes in peak knee extension moments (Right: p = 0.216; Left: p = 0.261). Increasing levels of breast support were associated with greater trunk flexion angles at initial contact (p = 0.024) and greater peak trunk flexion angles (p = 0.002).ConclusionsLower levels of breast support are associated with knee joint and trunk biomechanical profiles suggested to increase ACL injury risk.

Effects of a Medial Unloader Brace on Gait Mechanics in Patients with Osteochondritis Dissecans

Background:Non-operative treatment for osteochondritis dissecans (OCD) of the knee traditionally includes casting, bracing, and activity restrictions. An unloader brace is an option that may result in improved compliance due to the ability of the patient to continue daily activities while maintaining brace wear, and it may have biomechanical advantages for lesion healing. However, the biomechanical efficacy of a medial unloader brace has not been confirmed in a pediatric population.Hypothesis/Purpose:To determine whether the use of a medial unloader brace alters gait mechanics in patients with medial femoral condyle OCD. We hypothesized that while knee alignment in the coronal plane will remain unaltered, the valgus moment will decrease due to the applied tension of the adjusted unloader brace.Methods:Fifteen medial femoral condylar OCD patients (14 male, 12.7±2.6 years, 156.9±14.8 cm, and 52.0±16.2 kg) were tested utilizing a medial Ossur Unloader One knee brace. All patients performed over-ground walking at a self-selected speed under three brace conditions: no brace (NB), unadjusted (U), and adjusted (A; prescribed tension applied). Pelvis and lower extremity kinematic and kinetic data were computed in the sagittal, coronal, and transverse planes during single-limb stance phase (SLS). Wilcoxon signed-rank tests were performed to identify statistical differences between brace conditions (α=0.05), and clinical significance was only determined when statistically significant joint angle and moment differences were greater than 3° and 0.1Nm/kg, respectively.Results:Between braced conditions, mean knee valgus was not statistically significant, however, peak internal knee valgus moment consistently decreased with each brace condition (NB-A: 0.06 Nm/kg, p=0.017). Similarly, hip abduction moment at the second peak of SLS decreased while wearing the brace (NB-U: p=0.061, NB-A: 0.07 Nm/kg, p=0.009).Conclusion:Peak knee valgus moment was decreased during walking with an adjusted medial unloader brace. These results highlight potential biomechanical advantages of a medial unloader brace for medial femoral condylar OCD. Future work will measure compliance of brace wear and compare additional brace designs.Table 1.Coronal plane hip and knee kinematics and kinetics (Mean ± SD) for each brace condition.Figure 1.Average coronal knee angle and moment throughout gait cycle

Effects of shoe collar height and arch-support orthosis on joint stability and loading during landing

ABSTRACT This study examined the effects of shoe collar height and foot orthosis on ground reaction force (GRF), ankle and knee mechanics during landing. Sixteen male university basketball players performed drop landing when wearing different shoes with collar height (high vs. low) and foot orthoses (arch-support vs. flat). Biomechanical variables included vertical peak GRF and joint angles and moments in sagittal and coronal planes were analysed with two-way ANOVA with repeated measures (α = 0.05). Results indicated that high-collar shoes had significantly smaller peak ankle dorsiflexion (P < 0.001), smaller ankle sagittal total RoM (P < 0.001), higher forefoot peak GRF (P = 0.009) and peak knee valgus moment (P < 0.001) compared with low-collar shoes. Wearing arch-support orthoses induced higher forefoot peak GRF (P < 0.001) but smaller ankle inversion moment (P = 0.001) compared to flat-orthoses. Furthermore, significant interactions between collar-height and orthosis were found only for initial ankle plantarflexion (P = 0.023) and knee flexion (P = 0.035), but not in any kinetics variables. The findings suggest increased collar height and arch-support orthoses appear to reduce the risks of ankle sprains during landing, but might increase loading at adjacent joints.

Restricting ankle dorsiflexion does not mitigate the benefits of external focus of attention on landing biomechanics in healthy females.

Restricted ankle dorsiflexion can promote aberrant biomechanics associated with risk for knee injury during dynamic activities. Attentionally focused instructions have been used to improve high-risk knee biomechanics during landing tasks. Yet, it is unknown whether attentionally focused instruction can effectively improve landing patterns in the presence of a mechanical restriction on the ankle. Therefore, our purpose was to determine whether restricting ankle dorsiflexion by use of bracing mitigated the effects of attentional foci on landing biomechanics in healthy females. We used a crossover design to investigate lower extremity biomechanics in 19 healthy females between the ages of 18-35 during a series of jump-landing tasks. Participants completed 6 blocks of 3 jump-landings on separate force platforms in a randomized order based on brace condition (brace, no brace) and mode of attentional foci (neutral, internal focus [IF], external focus [EF]). Attentionally focused instructions were provided immediately prior to 3 practice jump-landings, followed by 5 test jump-landings with self-controlled feedback only. Ankle bracing decreased peak dorsiflexion and sagittal range of motion (ROM) (mean difference: 5.7-5.8°), and peak inversion and frontal ROM (mean difference: 2.4-3.0°). However, hip flexion ROM (mean difference: 1.8°) increased compared to the no brace condition. Regardless of ankle bracing, EF instruction increased peak hip flexion (mean difference: 4.9°) and hip flexion range of motion (mean difference: 3.8-4.6°), while decreasing peak knee valgus (mean difference: 0.8-1.0°) and knee valgus moment (mean difference: 0.04Nm/kg). Additionally, EF instruction increased peak hip abduction to a similar degree when braced (mean difference: 3.6-4.0°) and not braced (mean difference: 2.1-2.5°). Lastly, EF instruction increased hip abduction ROM only when braced (mean difference: 2.3-2.4°), but decreased peak knee valgus power only when not braced (mean difference: 0.18W/kg). Our findings indicate that mechanically restricting ankle dorsiflexion does not mitigate the ability of EF instruction to enhance jump-landing performance by means of improving hip and knee biomechanics in healthy females. However, our findings suggest an improved ability to control the rate of knee valgus loading when not braced. Therefore, we conclude that EF instruction remains a viable clinical strategy to improve landing patterns in the presence of restricted ankle dorsiflexion, yet this approach may be ineffective to reduce the rate of knee joint loading.

Association between ankle angle at initial contact and biomechanical ACL injury risk factors in male during self-selected single-leg landing

BackgroundIncreasing the ankle plantar-flexion angle at initial contact (IC) during landing reduces the impact features associated with landing, such as the vertical ground reaction force and loading rate, potentially affecting the risk of anterior cruciate ligament (ACL) injury. However, the relationships between the ankle plantar-flexion angle at IC and the previously identified biomechanical factors related to noncontact ACL injury have not been studied. Research questionThus, the purpose of this study was to determine whether significant relationships exist between the ankle plantar-flexion angle at IC and the biomechanical factors related to noncontact ACL injury. MethodsThe peak anterior tibial shear force, peak external knee valgus moment, peak knee valgus angle, and combined peak external knee valgus plus tibial internal rotation moments were measured in 26 individuals while performing self-selected, single-leg landing. Pearson correlation analyses were performed to assess the relationships between the ankle plantar-flexion angle at IC and the biomechanical factors mentioned above. ResultsThe greater ankle plantar-flexion angle at IC was related to smaller the peak knee valgus moment (r = −0.5, p = 0.009) and the combined peak knee valgus plus internal rotation moments (r = −0.58, p = 0.001). SignificanceThese results suggest that large ankle plantar-flexion angle at IC might be associated with lesser loading of the knee frontal plane and altering the self-selective ankle angle may result in biomechanical changes associated with ACL injury risk.

Correlations Between Dual-task Costs In Clinic Versus Laboratory Movements

Identifying increases in injury-relevant biomechanics when athletes are distracted by a secondary task may be important for assessing performance and injury risk in athletic environments. It is unknown if this dual task cost (DTC) measured during detailed motion capture testing is associated with DTC on simple clinical tests. Such a relationship may prove useful for improving clinically feasible return-to-play assessments. PURPOSE: Investigate whether dual-task ability spans clinical and laboratory methods of assessment. METHODS: Twenty-three female soccer players (21 ± 3yrs, 1.7 ± 0.1m, 64 ± 10kg) completed an agility drill requiring two 90° turns and one 180° turn. This was completed in isolation (baseline) and under three dual-task conditions: counting backwards by seven (S7), dribbling a soccer ball (BH), and combined ball dribbling and counting tasks (BHS7). Agility drill DTC (aDTC) was calculated as the percent change in completion time between dual-task and baseline conditions. A jump-land-jump task from a 30 cm box was also completed while 3D kinematics and kinetics were recorded. Dual task jump conditions included working memory (WM), working memory + visual attention task (WMV), and unanticipated working memory + visual attention task (UWMV) tasks. Biomechanical DTC (bDTC) was calculated as the percent change in peak knee valgus moment (pkVM) between dual-task jump landings and a single-task jump landing. Spearman’s rho correlations were run between all combinations of aDTC and bDTC (Figure 1).RESULTS: Increases in aDTC for the S7 condition were associated with increases in bDTC for the WMV (ρ=0.49, p=0.02) and the WM (ρ=0.43, p=0.04) conditions. No other relationships reached significance (i.e., p>0.05). CONCLUSION: Dual-task ability spanned clinical and laboratory assessments when the secondary task was an anticipated cognitive task. Further research is needed to establish the clinical utility of these relationships.

Effect of Sex on Anterior Cruciate Ligament Injury-Related Biomechanics During the Cutting Maneuver in Preadolescent Athletes.

Background:There are 2 movement patterns associated with an anterior cruciate ligament (ACL) injury: dynamic valgus and stiff landing. Although sex-dependent differences have been identified for adults, less is known for preadolescent athletes regarding movement patterns known to load the ACL.Hypothesis:We hypothesized that girls would demonstrate greater vertical ground reaction forces and knee valgus angles. We further hypothesized that the exercise intervention would affect girls more than boys and that this would primarily be demonstrated in less sagittal plane excursions, increased vertical ground reaction forces and knee valgus moments for girls than for boys.Study Design:Controlled laboratory study.Methods:Male and female soccer and handball players (n = 288; age range, 9-12 years) were recruited. A motion capture system synchronized to a force platform was used to record 5 trials of a cutting maneuver before and after a 5-minute fatigue intervention. Linear mixed models were constructed, and analysis of variance was used to analyze differences in outcomes associated with the sex of the athletes.Results:Boys showed greater peak knee valgus moment (0.26 vs 0.22 N·m/kg, respectively; P = .048), peak knee internal rotation moment (–0.13 vs –0.10 N·m/kg, respectively; P = .021), knee rotation excursion (–7.9° vs –6.9°, respectively; P = .014), and knee extension excursion (2.7° vs 1.4°, respectively; P < .001) compared with that in girls. A significant sex × fatigue intervention interaction (F = 7.6; P = .006) was found, which was caused by a greater increase in first peak vertical ground-reaction force (vGRF) from before to after the fatigue intervention for girls (15.3 to 16.0 N/kg) compared with boys (16.4 to 16.5 N/kg).Conclusion:Differences detected for biomechanical factors during the cutting maneuver do not point to a greater ACL injury risk for prepubescent or early pubescent girls than for boys. Nonetheless, girls go on to develop more detrimental movement patterns in adolescence than those in boys in terms of biomechanical risk factors.Clinical Relevance:Early adolescence is a good target age to learn and develop muscular control; balance, strength; flexibility; and jumping, running, and landing control. This time of physical and athletic growth may therefore be an appropriate period to influence biomechanical factors and thereby task execution and the injury risk.

By failing to prepare, you are preparing your anterior cruciate ligament to fail.

There is strong evidence linking an athlete's movement technique during sidestepping with anterior cruciate ligament (ACL) injury risk. However, it is unclear how these injuriouspostures are influenced by prior movement. We aim to describe preparatory trunk and thigh kinematics at toe-off of the penultimate-step and flight-phase angular momenta, and explore their associations with frontal-plane risk factors during unplanned sidestepping maneuvers. We analyzed kinematic and kinetic data of 33 male Australian Football players performing unplanned sidestepping tasks (103 trials). Linear mixed models tested for reliable associations between ACL injury risk during weight acceptance of the execution-step, with preparatory kinematics and angular momenta of the trunk and thigh during the penultimate-step. Multi-planar flight-phase trunk momenta along with hip abduction angle at penultimate-step toe-off were significantly associated with peak knee valgus moments during the execution-step (R2 =.21, P<.01). Execution-step trunk lateral flexion was significantly predicted by frontal and sagittal-plane preparatory trunk positioning at toe-off of the penultimate-step (R2 =.44, P<.01). Multi-planar flight-phase trunk momenta as well as multi-planar trunk and hip positioning at penultimate-step toe-offwere associated with hip abduction during the execution-step (R2 =.53, P<.01). Preparatory positioning of the trunk and hip, along with flight-phase trunk momentum adjusting this positioning are linked to known ACL injury risk factors. We recommendthat during the penultimate-step athletes maintain an upright trunk, as well as minimize frontal-plane trunk momentum and transverse-plane trunk momentum toward the sidestep direction to reduce risk of ACL injury during unplanned sidesteps.

A 2-yr Biomechanically Informed ACL Injury Prevention Training Intervention in Female Field Hockey Players

ABSTRACT Purpose Anterior cruciate ligament (ACL) injury prevention programs have been shown to have mixed success in reducing injury rates, raising the question whether these programs are effectively targeting biomechanical mechanisms of injury. The current study examined the efficacy of a biomechanically informed ACL injury prevention training program in reducing injury risk and injury incidence and investigated its effect on athletic performance. Participants Twenty-six elite female field hockey players participated in this study. Methods Athletes participated in a 2-yr injury prevention training program. Injury incidence (i.e., lower limb and ACL) and athletic performance (i.e., strength, speed, and aerobic power) were measured during a control season and after two intervention seasons. Biomechanical ACL injury risk factors were recorded during unplanned sidestepping at baseline and after intensive (9 wk: 4 × 20 min·wk−1) and maintenance (16 wk: 3 × 10 min·wk−1) training phases for a subset of athletes (n = 17). Results Training was effective in reducing ACL and lower limb injury incidence after the 2-yr program, where zero ACL injuries occurred after implementation (vs 0.4 per 1000 player hours in the control year). High-risk athletes reduced their peak knee valgus moments by 30% (P = 0.045) and demonstrated improvements in desirable muscle activation strategies after intensive training. The majority of benefits elicited in intensive training were retained during the maintenance phase. One-repetition max strength, beep test scores, and sprint times improved or were maintained over the 2-yr intervention period. Conclusions Biomechanically informed injury prevention training was successful in reducing both biomechanical ACL injury risk factors and ACL injury incidence while maintaining and/or improving athletic performance. It is important to consider the biomechanical mechanisms of injury when designing injury prevention programs.

Core-Muscle Training and Neuromuscular Control of the Lower Limb and Trunk.

Comprehensive injury-prevention training (plyometric, agility, balance, and core-stability exercises) has been shown to decrease sport-related injury. The relationship between trunk control and sport-related injury has been emphasized; however, the isolated effects of core-muscle training are unclear. To investigate the effect of a simple 8-week core-muscle-training program on the neuromuscular control of the lower limb and trunk during jump landing and single-legged squatting. Controlled laboratory study. Laboratory. Seventeen female collegiate basketball players were randomly divided into training (n = 9; age = 19.7 ± 0.9 years) and control (n = 8; age = 20.3 ± 2.5 years) groups. The training group completed the core-muscle-training program in addition to daily practice, and the control group performed only daily practice. Kinematic and kinetic data during a drop-jump test and single-legged squat were acquired using a 3-dimensional motion-analysis system. Three-dimensional hip, knee, and trunk kinematics; knee kinetics; and isokinetic muscle strength were measured at the pretraining and posttraining phases. For the drop-jump test, the maximal trunk-flexion angle increased (P = .008), and peak knee-valgus moment (P = .008) decreased in the training group. For the single-legged squat, the peak trunk-flexion angle increased (P = .04), and the total amount of trunk lateral-inclination angle (P = .02) and peak knee-valgus moment (P = .008) decreased in the training group. We observed no changes in the control group. A consecutive 8-week core-muscle-training program improved lower limb and trunk biomechanics. These altered biomechanical patterns could be favorable to preventing sport-related injuries.

The Biomechanical Effects of Fatigue on Drop-Jump Performance in Basketball Athletes

Anterior Cruciate Ligament (ACL) injuries have high occurrences in the sport of basketball due to the high amounts of landing, cutting, and other sudden deceleration maneuvers. During landing, studies have prospectively linked insufficient amounts of knee flexion, greater knee valgus angles, and greater knee valgus moments accompanied by greater vertical ground reaction force to increased risk of ACL injuries. These mechanisms have shown to be increased in a fatigued state therefore suggesting an athlete may be at greater risk for ACL injury when they are fatigued. Research to support this claim, however, is inconclusive. PURPOSE: To examine the difference in peak knee flexion angle (pKFA), peak knee valgus angle (pKVA), peak knee valgus moment (pKVM), and peak vertical ground reaction force (vGRF) pre and post fatigue during the landing phase of a drop jump task in basketball athletes. METHODS: Twenty-five subjects participated in the study and performed three drop jump trials before and after a fatigue protocol involving repeated counter movement jumps touching a customized target specific to each subject. Data was captured using a Qualisys 9-camera motion capture system sampling at 240-Hz and two AMTI force plates sampling at 2400-Hz. RESULTS: Paired t-tests showed subjects landed with significantly greater pKFA post fatigue (p < .05) while pKVA, pKVM, and pGRF showed no difference pre- and post-fatigue (p > .05). CONCLUSION: Subjects in this study adopted a safer landing strategy post fatigue, hence, suggesting our study did not support the claim that athletes would be at greater risk for ACL injuries in a fatigued state.

DOES A COMBINED INTRA-ARTICULAR AND EXTRA-ARTICULAR ACL RECONSTRUCTION EFFECT EXTERNAL KNEE VALGUS MOMENT ASYMMETRY?

Introduction: Peak external knee valgus moment can predict future ACL injury and is, often times, asymmetric following anatomic intra-articular ACL reconstruction. The purpose of this study is to evaluate the external knee valgus moment during a drop landing and a single limb squat 2 years following an iliotibial band (ITB) intra-articular and extra-articular physeal-sparing ACL reconstruction. Methods: Fourteen study subjects (mean age: 14.3 ± 2.6 yrs) who had previously undergone a physeal-sparing ACL reconstruction, as originally described by McIntosh using an ITB autograft, were enrolled in this IRB-approved study. All subjects were seen at a minimum of 24 months after surgery (mean follow-up: 55.0 ± 28.9 mos) and clinical, radiographic, and patient reported outcomes were collected. During functional testing, subjects underwent drop landing (DL) and unilateral squat (US) tasks. Isokinetic muscle strength of the hip and knee was collected using an isokinetic dynamometer at 60°/s. Paired student’s t-tests evaluated differences between affected (AFF) and unaffected (UNAFF) limbs. Results: During a drop landing, the AFF limb, compared to the UNAFF limb, did not demonstrate a difference in external knee valgus moment (0.50° vs. 0.51°, p=0.736). However, in the AFF limb, the mean knee peak knee valgus angle was 2.8 degrees less than the UNAFF limb during a drop landing (p=0.039). This difference was not considered within the range of a minimal clinical difference (MCD) of 5.1 degrees. Similar trends were found during a single limb squat with no significant difference seen in peak knee valgus moment between AFF and UNAFF (0.14° vs. 0.07°, p=0.150) with a statistical, yet not minimal clinical difference, in knee valgus angle at 45° squat position (-2.4° vs. 0.7°, p=0.033; MCD = 5.2). Thus, no asymmetry in peak knee valgus moment during a drop landing or a single limb squat following an ITB intra- and extra-articular ACL reconstruction was observed. In this series at 2 years’ post-op, the Pedi-IKDC and HSS Pedi-FABS were 96.54 ± 5 and 22.6 ± 5, respectively. Subjects demonstrated return to pre-operative Tegner Activity scores (8.42 vs. 8.17, p=0.33). Normalized hip abduction strength was significantly stronger in AFF (1.05 Nm/kg) vs. UNAFF (0.93 Nm/kg, p=0.02). Conclusion: Overall, there were no clinically significant differences, or asymmetry, in functional knee valgus in subjects following combined intra- and extra-articular iliotibial band ACL reconstruction during a drop landing or single leg squat. Young athletes can be expected to return to pre-operative activity levels and demonstrate appropriate knee valgus control following this physeal-sparing ACL reconstruction.

A Reliable Video-based ACL Injury Screening Tool for Female Team Sport Athletes.

This study aimed to develop a 2-dimensional (2D) video screening tool capable of predicting an athlete's peak 3-dimensional (3D) knee moments during unplanned sidestepping. 2D video-based kinematic measures were simultaneously captured with 3D peak knee moments for 30 female field hockey players (15 junior, 15 senior). Intra- and intertester repeatability of 2D kinematic measures was performed. Then, linear regression models were used to model 3D knee moments from 2D kinematic variables utilizing 80% of the sample (n=24). Regression equations were then validated on the remaining 20% of the sample (n=6). Angular 2D measures had good-excellent intra- (ICC=0.936-0.998) and intertester (ICC=0.662-0.949) reliability. Displacement measures had poor-excellent intra- (ICC=0.377-0.539) and inter-tester (ICC=0.219-0.869) reliability. Significant independent predictors of peak knee moments were dynamic knee valgus, knee flexion angle at foot strike, trunk flexion range of motion (ROM), trunk lateral flexion, hip abduction and knee flexion ROM (P<0.05). Regression equations generated from these models effectively predicted peak knee extension, valgus and internal rotation moments (i. e., were not different from measured values P>0.05, ES<0.4) in the 20% subsample. 2D video-based measurements of an athlete's full body kinematics during unplanned sidestepping provide a reliable, specific, sensitive and cost-effective means for screening female team sport athletes.