Gender, Vertical Height and Horizontal Distance Effects on Single-Leg Landing Kinematics: Implications for Risk of non-contact ACL Injury

Effect of Heading a Soccer Ball as an External Focus During a Drop Vertical Jump Task

Background

Research has demonstrated that performing a secondary task during a drop vertical jump (DVJ) may affect landing kinetics and kinematics.

Purpose

To examine the differences in the trunk and lower extremity biomechanics associated with anterior cruciate ligament (ACL) injury risk factors between a standard DVJ and a DVJ while heading a soccer ball (header DVJ).

Study Design

Descriptive laboratory study.

Methods

Participants comprised 24 college-level soccer players (18 female and 6 male; mean ± SD age, 20.04 ± 1.12 years; height, 165.75 ± 7.25 cm; weight, 60.95 ± 8.47 kg). Each participant completed a standard DVJ and a header DVJ, and biomechanics were recorded using an electromagnetic tracking system and force plate. The difference (Δ) in 3-dimensional trunk, hip, knee, and ankle biomechanics between the tasks was analyzed. In addition, for each biomechanical variable, the correlation between the data from the 2 tasks was calculated.

Results

Compared to the standard DVJ, performing the header DVJ led to significantly reduced peak knee flexion angle (Δ = 5.35°; P = .002), knee flexion displacement (Δ = 3.89°; P = .015), hip flexion angle at initial contact (Δ = -2.84°; P = .001), peak trunk flexion angle (Δ = 13.11°; P = .006), and center of mass vertical displacement (Δ = -0.02m; P = .010), and increased peak anterior tibial shear force (Δ = -0.72 N/kg; P = .020), trunk lateral flexion angle at initial contact (Δ = 1.55°; P < .0001), peak trunk lateral flexion angle (Δ = 1.34°; P = .003), knee joint stiffness (Δ = 0.002 N*m/kg/deg; P = .017), and leg stiffness (Δ = 8.46 N/kg/m; P = .046) compared to those in standard DVJs. In addition, individuals' data for these variables were highly and positively correlated between conditions (r = 0.632-0.908; P < .001).

Conclusion

The header DVJ task showed kinetic and kinematic parameters that suggested increased risk of ACL injury as compared with the standard DVJ task.

Clinical Relevance

Athletes may benefit from acquiring the ability to safely perform header DVJs to prevent ACL injury. To simulate real-time competition situations, coaches and athletic trainers should incorporate such dual tasks in ACL injury prevention programs.

Retrospective analysis and risk of progression of partial anterior cruciate ligament injuries in a young population

BACKGROUND

The anterior cruciate ligament (ACL) is a common knee ligament injury. Partial ACL tears are common, and at least 10-27% of isolated ACL tears are diagnosed as partial tears. Patients with partial tears have high risk of progression of tears to complete tears, which may require surgical reconstruction. The risk factors associated with the progression to a complete tear are poorly understood.

METHODS

The present case-control study assessed the incidence and risk factors for the progression of conservatively treated partial ACL tears to complete tears in 351 patients younger than 45 years. The diagnosis of partial ACL tears was based on clinical evaluation, side-to-side difference on Rolimeter, and magnetic resonance imaging. These patients were managed conservatively and followed up for a mean of 17.5 months or until the progression of the tear into a complete tear, requiring surgery. The patients in whom the tear progressed to complete tear (group P) were compared with those in whom the tear remained stable for a minimum of 18-month follow-up period (group S).

RESULTS

Of the 351 partial ACL tear patients, 166 (47.3%) patients progressed to a complete tear at a mean duration of 17.5 months, whereas the tear in 185 (52.7%) patients remained stable and did not progress to a complete tear. Group P had mean international knee documentation committee (IKDC) scores and Tegner scores of 95.7 ± 3.7 and 7.6 ± 1.6, respectively, before the injury, and scores decreased to 52.4 ± 4.1 and 5.7 ± 2.2, respectively, at the 24-month follow-up.

CONCLUSION

Partial ACL tear progressed to a complete tear in 47.3% of evaluated patients. The associated risk factors were age less than 35 years, rigorous physical activities, high ACL-Return to Sport after Injury score during early rehabilitation days, early return to activity, and pivoting contact sports.

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.

What did the ankle say to the knee? Estimating knee dynamics during landing - A systematic review and meta-analysis

BACKGROUND

Landing-based measures of the knee are often used to assess risk of anterior cruciate ligament (ACL) injury and inform prevention strategies. There is less understanding of the ankle's influence on knee measures during landing.

OBJECTIVE

1. Examine interactions of dynamic ankle measures alongside various subject and task characteristics on knee dynamics in vertical landing and 2. Determine whether ankle measures alone can estimate dynamic knee measures associated with ACL injury risk.

DESIGN

Systematic review and meta-analysis.

METHODS

Electronic databases Medline, EMBASE, CINAHL, Web of Science and Cochrane were screened for studies that included measurement of initial contact angles and internal joint moments of both the ankle and knee during landing in uninjured individuals.

RESULTS

28 studies were included for analysis. Using 1144 landing trials from 859 individuals, RRelief F algorithm ranked dynamic ankle measures more important than landing task and subject characteristics in estimating knee dynamics. An adaptive boosting model using four dynamic ankle measures accurately estimated knee extension (R² = 0.738, RMSE = 3.65) and knee abduction (R² = 0.999, RMSE = 0.06) at initial contact and peak knee extension moment (R² = 0.988, RMSE = 0.13) and peak knee adduction moment (R² = 1, RMSE = 0.00).

CONCLUSIONS

Dynamic ankle measures can accurately estimate initial contact angles and peak moments of the knee in vertical landing, regardless of landing task or individual subject characteristics. This study provides a theoretical basis for the importance of the ankle in ACL injury prevention.

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.

Dynamic Knee Valgus in Single-Leg Movement Tasks. Potentially Modifiable Factors and Exercise Training Options. A Literature Review

Dynamic knee valgus (DKV) as an incorrect movement pattern is recognized as a risk factor for lower limb injuries. Therefore, it is important to find the reasons behind this movement to select effective preventive procedures. There is a limited number of publications focusing on specific tasks, separating the double-leg from the single-leg tasks. Test patterns commonly used for DKV assessment, such as single-leg squat (SLS) or single leg landings (SLL), may show different results. The current review presents the modifiable factors of knee valgus in squat and landing single-leg tests in healthy people, as well as exercise training options. The authors used the available literature from PubMed, Scopus, PEDro and clinicaltrials.gov databases, and reviewed physiotherapy journals and books. For the purpose of the review, studies were searched for using 2D or 3D motion analysis methods only in the SLL and SLS tasks among healthy active people. Strengthening and activating gluteal muscles, improving trunk lateral flexion strength, increasing ROM dorsiflexion ankle and midfoot mobility should be taken into account when planning training programs aimed at reducing DKV occurring in SLS. In addition, knee valgus during SLL may occur due to decreased hip abductors, extensors, external rotators strength and higher midfoot mobility. Evidence from several studies supports the addition of biofeedback training exercises to reduce the angles of DKV.

Mechanical Differences Between Adolescents and Adults During Two Landing Phases of a Drop Jump Task

Moir, GL, Munford, SN, Snyder, BW, and Davis, SE. Mechanical differences between adolescents and adults during two landing phases of a drop jump task. J Strength Cond Res XX(X): 000-000, 2020-The mechanical differences between the first and second landing phases of a drop jump (DJ) task performed by adolescent and adult male players were investigated. Eleven adolescent basketball players (age: 16.5 ± 0.7 years) and 11 resistance-trained adults (age: 22.3 ± 1.9 years) performed DJs from a height of 0.40 m. Force plates and a 3-dimensional motion analysis system were used to determine mechanical variables, including landing velocity, normalized vertical stiffness, normalized peak impact force, and work as well as mechanical characteristics of the hip, knee, and ankle joints during the absorption phase of each landing. The adolescents produced greater peak impact forces (mean difference [xDiff] = 42 N·kg; effect size [ES] = 1.15) and vertical stiffness (xDiff = 126 N·kg·m; ES = 1.28) during shorter absorption phases (xDiff = 0.09 seconds; ES = 2.67) compared with the adults, despite their lower landing velocities (xDiff = 0.21 m·s; ES = 1.37). Furthermore, the adolescents generated greater peak extensor joint moments at the lower-body joints compared with the adults (xDiff = 2.3 N·m·kg; ES = 1.17), but they did not effectively modulate the energy absorbed by the joint moments in response to the changing demands of the landing tasks. The assessment of the biomechanical characteristics of the 2 landing phases associated with a DJ task revealed that adolescent male basketball players adopt neuromuscular strategies that may increase the risk of incurring musculoskeletal injuries compared with resistance-trained adults.

Differentiating Successful and Unsuccessful Single-Leg Drop Landing Performance Using Uncontrolled Manifold Analysis

Biomechanical analysis can effectively identify factors associated with task performance and injury risk, but often does not account for the interaction among the components that underlie task execution. Uncontrolled manifold (UCM) analyses were applied to data from 38 female, adolescent athletes performing single-leg drop landings and were used to differentiate successful and unsuccessful task performance by examining the frontal plane joint variance within the UCM (VUCM) that stabilized the horizontal center of mass position (VUCM) and within the orthogonal subspace (VORT). The UCM revealed stronger coordination, indicated by the VUCM/VORT ratio, in the successful condition. This may inform future research examining reduced motor coordination in failed movement tasks and its relation to injury risk and allow for targeted interventions that consider coordination processes rather than joint-specific outcomes.

Eliminating high-intensity activity during growth reduces mechanical power capacity but not submaximal metabolic cost in a bipedal animal model

Decreases in activity levels in children worldwide are feared to have long-term health repercussions. Yet, because of the difficulty of performing controlled long-term studies in humans, we do not yet understand how decreases in childhood activity influence adult functional capacity. Here, in an avian bipedal model, we evaluated the elimination of all high-intensity activity during growth on adult performance. We evaluated three alternative hypotheses: Elimination of high-intensity activity 1) does not influence adult function, 2) results in task-specific deficits in adulthood, or 3) results in deficits that generalize across locomotor tasks. We found that animals restricted from jumping and sprinting during growth showed detriments as adults in maximal jump performance in comparison to controls, but did not require more metabolic energy during steady-state running or standing. From this, we conclude that functional deficits from elimination of high-intensity exercise are task specific and do not generalize across all locomotor functions.NEW & NOTEWORTHY Decreasing childhood activity levels are feared to have long-term health repercussions, but testing this hypothesis is hampered by restrictions of human experimentation. Here, in a bipedal animal model, we examine how the elimination of high-intensity activity during all of maturation influences adult locomotor capacity. We found restricted activity during growth reduced mechanical power capacity but not submaximal metabolic cost. This suggests that reduced childhood activity may result in task-specific, rather than generalized locomotor deficits.

Effects of different oral instructions on kinematic and kinetic parameters during drop vertical jump

[Purpose] This study aimed to examine the impact of changing the drop vertical jump stance time on kinematic and kinetic parameters by ordering to high jump or quick jump for consistent stance time and a more accurate assessment of anterior cruciate ligament injury risk. [Participants and Methods] The participants were 20 healthy female students. The drop vertical jump was started by instructing the participants to stand on a 30-cm platform with both legs stationary. The task was performed while the participants were instructed to perform high jump or quick jump. [Results] Stance time was significantly shorter with quick jump than with high jump. Quick jump showed significantly higher knee abduction angles at initial contact and peak vertical ground reaction force, and lower hip flexion, knee flexion, and ankle dorsiflexion angles at the lowest point of the center of mass. Quick jump showed a significantly higher peak vertical ground reaction force. The knee abduction moment at initial contact was not significantly different between the 2 conditions. [Conclusion] Quick jump was better than high jump for making stance time consistent, and the differences in kinematic and kinetic characteristics by oral instructions should be considered when using drop vertical jump.

Limb-dominance and gender differences in the ground reaction force during single-leg lateral jump-landings

[Purpose] The purpose of this study was to examine limb-dominance and gender differences in the magnitude of the ground reaction force during single-leg lateral jump-landings. We hypothesized that the peak ground reaction force would be larger in the non-dominant leg compared to that in the dominant leg and would be larger in females compared to that in men. [Subjects and Methods] Fifteen females and 15 males performed jump-landings sideways from a height of 20 cm, with a lateral distance of 60 cm. Vertical and medial ground reaction forces were measured, and the elapsed time from the initial contact to the peak ground reaction force was determined. The loading rate was calculated as the peak ground reaction force divided by the elapsed time from the initial contact to the peak ground reaction force. [Results] The vertical and medial peak ground reaction forces during single-leg lateral jump-landings were larger in females compared to that in males. In addition, the medial peak ground reaction force was larger for the non-dominant leg compared to that for the dominant leg. [Conclusion] The results suggest that in rehabilitation and conditioning settings, evaluations and instructions regarding attenuation are especially important for females and the non-dominant leg.

Relation between peak knee flexion angle and knee ankle kinetics in single-leg jump landing from running: a pilot study on male handball players to prevent ACL injury

OBJECTIVES

The relationship between knee kinematics and knee-ankle kinetics during the landing phase of single leg jumping has been widely studied to identify proper strategies for preventing non-contact ACL injury. However, there is a lack of study on knee-ankle kinetics at peak knee flexion angle during jumping from running. Hence, the purpose of this study is to establish the relationship between peak knee flexion angle, knee extension moment, ankle plantar flexion moment and ground reaction force in handball players in order to protect ACL from excessive stress during single leg jumping. In addition, the study also clarifies the role of calf muscles in relieving part of ACL stresses with different knee flexion angles during landing.

METHODS

Fifteen active male elite handball players of Saudi Arabia have participated in this study (Age = 22.6 ± 3.5years, Height = 182 ± 3.7 cm, Weight = 87.5 ± 10.2 kg). The players performed three successful landings of single-leg jump following running a fixed distance of about 450cm. The data were collected using a 3D motion capture and analysis system (VICON).

RESULTS

Pearson product moment correlation coefficients showed that greater peak knee flexion angle is related significantly to both lesser knee extension moment (r = -.623, P = .013) and vertical component of ground reaction force (VGRF) (r = -.688, P = .005) in landing phase. Moreover, increasing the peak knee flexion angle in landing phase tends to increase the ankle plantar flexion moment significantly (r = .832, P = .000).

CONCLUSION

With an increase of the peak knee flexion angle during single leg jump landing from running, there would be less knee extension moment, low impact force and more plantar flexion moment. As such, the clinical implication of this study is that there may be a possible protective mechanism by increasing the knee flexion angle during landing phase, which tends to protect the ACL from vigorous strain and injuries.

Correlations between sagittal plane kinematics and landing impact force during single-leg lateral jump-landings

[Purpose] The correlations of peak vertical ground reaction force and sagittal angles during single-leg lateral jump-landing with noncontact anterior cruciate ligament injury remain unknown. This study aimed to clarify the correlations between kinematics and impact force during lateral jump-landing. [Subjects and Methods] Twenty active males were included in the analysis. A sagittal-view movie camera and force plate were time synchronized. Trunk and lower extremity sagittal angles were measured 100 ms before initial contact and at peak vertical ground reaction force. Peak vertical ground reaction force, time between initial contact and peak vertical ground reaction force, and loading rate were calculated. [Results] The mean sagittal angle was 40.7° ± 7.7° for knee flexion during the flight phase and 16.4° ± 6.3° for pelvic anterior inclination during the landing phase. The mean peak vertical ground reaction force was four times the body weight. The median time to peak vertical ground reaction force was 63.8 ms. The knee flexion during the flight phase and pelvic anterior inclination angles during the landing phase were related to the peak vertical ground reaction force. [Conclusion] Increasing knee flexion and decreasing pelvic anterior inclination might reduce the impact during single-leg lateral jump-landing.

Substantiating Appropriate Motion Capture Techniques for the Assessment of Nordic Walking Gait and Posture in Older Adults

Nordic walking (NW) has become a safe and simple form of exercise in recent years, and in studying this gait pattern, various data collection techniques have been employed, each with positives and negatives. The aim was to determine the effect of NW on older adult gait and posture and to determine optimal use of different data collection systems in both short and long duration analysis. Gait and posture during NW and normal walking were assessed in 17 healthy older adults (age: 69 ± 7.3). Participants performed two trials of 6 Minute Walk Tests (6MWT) (1 with poles (WP) and 1 without poles (NP)) and 6 trials of a 5m walk (3 WP and 3 NP). Motion was recorded using two systems, a 6-sensor accelerometry system and an 8-camera 3-dimensional motion capture system, in order to quantify spatial-temporal, kinematic, and kinetic parameters. With both systems, participants demonstrated increased stride length and double support and decreased gait speed and cadence WP compared to NP (p <0.05). Also, with motion capture, larger single support time was found WP (p <0.05). With 3-D capture, smaller hip power generation and moments of force were found at heel contact and pre-swing as well as smaller knee power absorption at heel contact, pre-swing, and terminal swing WP compared to NP, when assessed over one cycle (p <0.05). Also, WP yielded smaller moments of force at heel contact and terminal swing along with larger moments at mid-stance of a gait cycle (p <0.05). No changes were found for posture. NW seems appropriate for promoting a normal gait pattern in older adults. Three-dimensional motion capture should primarily be used during short duration gait analysis (i.e. single gait cycle), while accelerometry systems should be primarily employed in instances requiring longer duration analysis such as during the 6MWT.

Bilateral and unilateral vertical ground reaction forces and leg asymmetries in soccer players

The purposes of this study were to assess unilateral and bilateral vertical jump performance characteristics, and to compare the vertical ground reaction force characteristics of the impulse and landing phase of a vertical jump between the dominant and non-dominant leg in soccer players. The sample consisted of 20 male soccer players (22.80 ± 2.71 years, 1.88 ± 0.06 m, 76.47 ± 8.80 kg) who competed in the third division of the Spanish football league. Vertical jump performance was determined by testing the impulse and landing phase of a bilateral vertical jump, dominant leg vertical jump and non-dominant leg vertical jump. Significant differences (p < 0.05) between dominant and non-dominant legs were found in counter movement jump (CMJ) flight time (LA = -2.38%, d = 0.33), CMJ flight height (LA = -4.55%, d = 0.33) and CMJ speed take-off (LA = -2.91%, d = 0.42). No significant differences were found between the dominant and non-dominant leg in the F1 and F2 magnitudes during the landing phase, the time from the first contact of the foot with the ground to the production of F1, the time from the second contact of the foot with the ground to the production of F2, and the time to stabilization of the landing phase. Although differences were found between the dominant and non-dominant leg in the impulse phase of the jump, no significant differences were found between dominant and non-dominant legs in the landing phase of vertical jump variables.

Young Athletes With Quadriceps Femoris Strength Asymmetry at Return to Sport After Anterior Cruciate Ligament Reconstruction Demonstrate Asymmetric Single-Leg Drop-Landing Mechanics

BACKGROUND

Young athletes who have had anterior cruciate ligament (ACL) reconstruction demonstrate suboptimal rates of return to sport, high rates of second ACL injuries, and persistent movement asymmetries. Therefore, the influence of musculoskeletal impairments on movement mechanics in this population needs to be further evaluated.

HYPOTHESIS

The primary hypothesis was that among young athletes who have had ACL reconstruction, those with greater quadriceps strength asymmetry would demonstrate altered single-leg drop-landing mechanics at return to sport compared with individuals with more symmetric quadriceps strength and also compared with healthy controls (ie, those with no ACL reconstruction). A second hypothesis was that quadriceps strength symmetry would predict single-leg drop-landing symmetry in individuals who have undergone ACL reconstruction.

STUDY DESIGN

Controlled laboratory study.

METHODS

The study entailed a total of 103 participants (age, 17.4 years) at the time of return to sport after ACL reconstruction and 47 control participants (age, 17.0 years). The quadriceps index (QI) was calculated for isometric quadriceps strength, which was then used to divide the ACL reconstruction participants into high-quadriceps (QI ≥90%; n = 52) and low-quadriceps (QI <85%; n = 41) subgroups. Biomechanical data were collected by use of 3-dimensional motion analysis during a single-leg drop-landing task. The LSI was calculated for kinematic and kinetic sagittal-plane variables of interest during landing. Group differences were compared by use of 1-way analysis of variance and linear regression analyses (α < .05).

RESULTS

Both the low- and high-quadriceps groups demonstrated greater limb asymmetry during landing compared with the control group in knee flexion excursion (mean LSI ± SD: low quadriceps, 85.8% ± 15.5% [P < .001]; high quadriceps, 94.2% ± 15.6% [P = .019]; control, 102.7% ± 14.1%), peak trunk flexion angle (low quadriceps, 129.2% ± 36.6% [P < .001]; high quadriceps, 110.5% ± 22.6% [P = .03]; control, 95.5% ± 26.2%), and peak knee extension moment (low quadriceps, 79.5% ± 25.2% [P < .001]; high quadriceps, 89.9% ± 19.8% [P = .005]; control, 102.2% ± 10.9%). Compared with the high-quadriceps group, the low-quadriceps group also demonstrated greater asymmetry during landing in knee flexion excursion (P = .026), peak trunk flexion angle (P = .006), and peak knee extension moment (P = .034). In the ACL reconstruction group, quadriceps strength symmetry predicted symmetry in knee flexion excursion, peak trunk flexion, and peak knee extension moment (all P < .001) and predicted symmetry in peak trunk flexion angle (P < .001) after controlling for graft type, knee-related pain, function with activities of daily living, and sport function.

CONCLUSION

At the time of return to sport, athletes who had undergone ACL reconstruction, including those in both the high- and low-quadriceps groups, demonstrated asymmetry during a single-leg drop-landing task compared with controls. Compensations included increased trunk flexion, decreased knee flexion excursion, and decreased knee extension moments on the involved limb. In addition, individuals in the low-quadriceps group demonstrated greater movement asymmetry compared with individuals in the high-quadriceps group.

CLINICAL RELEVANCE

Restoration of symmetric quadriceps strength after ACL reconstruction is associated with more symmetric mechanics during a single-leg drop-landing movement. However, this appears to be multifactorial, as the high-quadriceps group also demonstrated landing asymmetries. Restoration of symmetric quadriceps strength may improve postoperative athletic participation; however, future study is warranted.

The effect of ankle bracing on lower extremity biomechanics during landing: A systematic review

OBJECTIVES

To examine the evidence for effect of ankle bracing on lower-extremity landing biomechanics.

DESIGN

Literature review.

METHODS

Systematic search of the literature on EBSCO health databases. Articles critiqued by two reviewers.

RESULTS

Ten studies were identified which investigated the effect of ankle bracing on landing biomechanics. Overall results suggest that landing biomechanics are altered with some brace types but studies disagree as to the particular variables affected.

CONCLUSIONS

There is evidence that ankle bracing may alter lower-extremity landing biomechanics in a manner which predisposes athletes to injury. The focus of studies on specific biomechanical variables rather than biomechanical patterns, analysis of pooled data means in the presence of differing landing styles between participants, variation in landing-tasks investigated in different studies, and lack of studies investigating goal-directed sport-specific landing tasks creates difficulty in interpreting results. These areas require further research.

What is normal? Female lower limb kinematic profiles during athletic tasks used to examine anterior cruciate ligament injury risk: a systematic review

BACKGROUND

It has been proposed that the performance of athletic tasks where normal motion is exceeded has the potential to damage the anterior cruciate ligament (ACL). Determining the expected or 'normal' kinematic profile of athletic tasks commonly used to assess ACL injury risk can provide an evidence base for the identification of abnormal or anomalous task performances in a laboratory setting.

OBJECTIVE

The objective was to conduct a systematic review of studies examining lower limb kinematics of females during drop landing, drop vertical jump, and side-step cutting tasks, to determine 'normal' ranges for hip and knee joint kinematic variables.

DATA SOURCES

An electronic database search was conducted on the SPORTDiscus(TM), MEDLINE, AMED and CINAHL (January 1980-August 2013) databases using a combination of relevant keywords.

STUDY SELECTION

Studies identified as potentially relevant were independently examined by two reviewers for inclusion. Where consensus could not be reached, a third reviewer was consulted. Original research articles that examined three-dimensional hip and knee kinematics of female subjects during the athletic tasks of interest were included for review. Articles were excluded if subjects had a history of lower back or lower limb joint injury or isolated data from the female cohort could not be extracted.

STUDY APPRAISAL AND SYNTHESIS METHODS

Two reviewers independently assessed the quality of included studies. Data on subject characteristics, the athletic task performed, and kinematic data were extracted from included studies. Studies were categorised according to the athletic task being examined and each study allocated a weight within categories based on the number of subjects assessed. Extracted data were used to calculate the weighted means and standard deviations for hip and knee kinematics (initial contact and peak values). 'Normal' motion was classified as the weighted mean plus/minus one standard deviation.

RESULTS

Of 2,920 citations, a total of 159 articles were identified as potentially relevant, with 29 meeting all inclusion/exclusion criteria. Due to the limited number of studies available examining double-leg drop landings and single-leg drop vertical jumps, insufficient data was available to include these tasks in the review. Therefore, a total of 25 articles were included. From the included studies, 'normal' ranges were calculated for the kinematic variables of interest across the athletic tasks examined.

LIMITATIONS

Joint forces and other additional elements play a role in ACL injuries, therefore, focusing solely on lower limb kinematics in classifying injury risk may not encapsulate all relevant factors. Insufficient data resulted in no normal ranges being calculated for double-leg drop land and single-leg drop vertical jump tasks. No included study examined hip internal/external rotation during single-leg drop landings, therefore ranges for this kinematic variable could not be determined. Variation in data between studies resulted in wide normal ranges being observed across certain kinematic variables.

CONCLUSIONS

The ranges calculated in this review provide evidence-based values that can be used to identify abnormal or anomalous athletic task performances on a multi-planar scale. This may be useful in identifying neuromuscular factors or specific muscular recruitment strategies that contribute to ACL injury risk.