Efficacy of ACL injury risk screening methods in identifying high-risk landing patterns during a sport-specific task.

Screening methods sensitive to movement strategies that increase anterior cruciate ligament (ACL) loads are likely to be effective in identifying athletes at-risk of ACL injury. Current ACL injury risk screening methods are yet to be evaluated for their ability to identify athletes' who exhibit high-risk lower limb mechanics during sport-specific maneuvers associated with ACL injury occurrences. The purpose of this study was to examine the efficacy of two ACL injury risk screening methods in identifying high-risk lower limb mechanics during a sport-specific landing task. Thirty-two female athletes were screened using the Landing Error Scoring System (LESS) and Tuck Jump Assessment. Participants' also completed a sport-specific landing task, during which three-dimensional kinematic and kinetic data were collected. One-dimensional statistical parametric mapping was used to examine the relationships between screening method scores, and the three-dimensional hip and knee joint rotation and moment data from the sport-specific landing. Higher LESS scores were associated with reduced knee flexion from 30 to 57 ms after initial contact (P = 0.003) during the sport-specific landing; however, no additional relationships were found. These findings suggest the LESS and Tuck Jump Assessment may have minimal applicability in identifying athletes' who exhibit high-risk landing postures in the sport-specific task examined.

Effects of maturation on combined female muscle strength and ACL structural factors.

OBJECTIVES: Relations between lower limb muscle strength and female ACL injury risk are well documented. How these relations combine with key ACL geometries however, is unknown. Identifying how these combined factors are impacted by maturation would benefit current risk screening and prevention efforts. This study compared hamstrings and quadriceps strength and ACL cross sectional area (CSA) indices across three maturation groups. DESIGN: Cross-sectional human experimental. METHODS: MRI scans of the dominant knee were collected in 35 females stratified into early (9.7±0.8yrs), middle (12.9±1.7yrs), and late (14.8±0.6yrs) maturation groups. Hamstring and quadriceps muscle volumes and ACL CSA measures were obtained. Isokinetic strength data were quantified for dominant knee flexors and extensors. Peak hamstring and quadriceps concentric and eccentric strength per unit volume magnitudes (QCSPV, HCSPV, QESPV, HESPV) were determined. Metrics and select ratios were submitted to a one way ANOVA to determine the main effect of maturation. RESULTS: Significant decreases occurred in HESPV (N/cm(3)) and ACL CSA (cm(2)/kgm), respectively, from early (0.188±0.023N/cm(3), 0.007±0.002cm(2)/kgm) to middle (0.157±0.029N/cm(3), 0.005±0.002cm(2)/kgm, p=0.034, p=0.029), and middle to late (0.132±0.031N/cm(3), 0.003±0.001cm(2)/kgm, p=0.044, p=0.018) maturation. A significant decrease in HESPV:QCSPV occurred between early (1.795±0.496) and middle (1.362±0.277, p=0.018) maturation. QCSPV: ACL CSA was significantly greater in late (37.26±13.35) compared to middle (25.81±9.17, p=0.021) maturation. CONCLUSIONS: Key ratios between female knee quadriceps and hamstring strength and ACL size parameters, which may directly impact ACL injury risk, are substantially different among three maturation states. The results are potentially hazardous strength mismatches in mid-pubertal females, where a smaller (weaker) ACL may be unable to stabilize quadriceps dominated loading strategies.

Associations between lower limb muscle activation strategies and resultant multi-planar knee kinetics during single leg landings.

OBJECTIVES: Anterior cruciate ligament injury prevention programs purportedly improve knee joint loading through beneficial modification of lower limb neuromuscular control strategies and joint biomechanics, but little is known about how these factors relate during single-legged landings. Thus, we examined the relationship between explicit lower limb muscular pre-activity patterns and knee joint biomechanics elicited during such landings. DESIGN: Randomized controlled trial. METHODS: Thirty-five female athletes had 3D knee joint biomechanics and lower limb EMG data recorded during a series of single-leg landings. Regression analysis assessed the relationship between pre-activity of vastus lateralis, lateral hamstring and rectus femoris with peak knee flexion angle and moment, and external anterior tibial shear force. Vastus lateralis, lateral hamstring and vastus lateralis:lateral hasmtring co-contraction assessed the relationship with knee abduction angle and moment. RESULTS: Greater pre-activity of rectus femoris predicted increased peak anterior tibial shear force (R(2)=0.235, b=2.41 and P=0.003) and reduced knee flexion moment (R(2)=0.131, b=-0.591, and P=0.032), while greater lateral hamstring predicted decreased peak knee flexion angle (R(2)=0.113, b=8.96 and P=0.048). No EMG pre-activity parameters were predictors (P>0.05) for knee abduction angle and moment. CONCLUSIONS: Current outcomes suggest reducing reliance on quadriceps activation may be beneficial during single-legged landings. It also, however, may be required for adequate joint stability during such maneuvers. Further research is needed to determine if inadequate hamstring activation, rather than elevated quadriceps activation, leads to hazardous loading during single-legged landings.

Isolated hip and ankle fatigue are unlikely risk factors for anterior cruciate ligament injury.

Lower extremity neuromuscular fatigue purportedly increases anterior cruciate ligament (ACL) injury risk through promotion of extreme landing mechanics. However, the impact of fatigue on muscle groups critical to the landing strategy remains unclear. This study examined the effects of isolated hip rotator and triceps surae fatigue on lower extremity landing biomechanics. Sixteen healthy females (18-22 years) reported for testing on two occasions, with one muscle group fatigued per session. Subjects performed three single-leg landings onto a force platform pre- and post-fatigue, defined as an 80% decrease in peak torque in the targeted muscle group. Hip rotator fatigue was induced via alternating concentric contractions and triceps surae fatigue through concentric plantar flexion contractions on an isokinetic dynamometer. Initial contact (IC) kinematics and peak stance (PS) kinetics and kinematics were analyzed pre- and post-fatigue. Hip rotator fatigue increased IC (P=0.05) and PS (P=0.04) hip internal rotation angles. Triceps surae fatigue decreased IC knee flexion (P=0.01) angle. Isolated hip rotator and triceps surae fatigue each produced modifications in lower limb kinematic parameters viewed as risk factors for ACL injury. These modifications, however, do not appear of sufficient magnitude to compromise ligament integrity, suggesting injury via an integrative lower extremity fatigue mechanism is more likely.

Sex and limb differences in hip and knee kinematics and kinetics during anticipated and unanticipated jump landings: implications for anterior cruciate ligament injury.

OBJECTIVES: In this study, the effects of temporal changes in unanticipated (UN) prelanding stimuli on lower limb biomechanics and the impact of sex and limb dominance on these variables during single-leg landings were determined. It was hypothesised that reductions in the time of prelanding UN stimuli, female sex, and the non-dominant limb would significantly increase high-risk landing biomechanics during UN jump landings. METHODS: 26 (13 men and 13 women) had initial contact (IC) and peak stance (0-50%) phase (PS) lower limb joint kinematics and kinetics quantified during anticipated (AN) and UN single-leg (left and right) landings. Postlanding jump direction was governed via one of two randomly ordered light stimuli, presented either before initiation of the jump (AN), or 600 ms (UN1), 500 ms (UN2) or 400 ms (UN3) immediately before ground contact. RESULTS: Statistically significant (p<0.05) differences in IC hip posture and PS hip and knee internal rotation moments occurred in UN compared with AN landings. Differences were not observed, however, among UN conditions for any biomechanical comparisons. Significant (p<0.05) differences in specific IC and PS hip and knee postures and loads occurred between sexes and limbs. Neither of these factors, however, influenced movement condition effects. CONCLUSION: UN landings induce modifications in landing biomechanics that may increase anterior cruciate ligament injury risk in both men and women. These modifications, however, do not appear overly sensitive to the timing of the UN stimulus, at least within a temporal range affording a successful movement response. Expanding UN training to include even shorter stimulus-response times may promote the additional central control adaptations necessary to manoeuvre safely within the random sports setting.

Evaluation of a two dimensional analysis method as a screening and evaluation tool for anterior cruciate ligament injury.

BACKGROUND: Increased knee valgus predicts the risk of anterior cruciate ligament (ACL) injury, particularly in women. Reducing injury rates thus relies on detecting and continually evaluating people with relatively large valgus motions. OBJECTIVES: To examine the potential of a two dimensional (2D) video analysis method for screening for excessive valgus. METHODS: Ten female and 10 male National Collegiate Athletic Association basketball players had three dimensional (3D) knee valgus and two dimensional (2D) frontal plane knee angle quantified during side step, side jump, and shuttle run tasks. 3D valgus was quantified from external marker coordinates using standard techniques, and 2D data were obtained from both the frontal plane projections of these coordinates (2D-Mot) and manual digitization of digital video footage (2D-Cam). A root mean square (RMS) error was calculated between 2D-Mot and 2D-Cam data to evaluate the reliability of the latter. Correlations between 2D-Cam and 3D data (intersubject and intrasubject) were also conducted, and regression slope and r2 values obtained. RESULTS: 2D-Cam and 2D-Mot data were consistent for side step (RMS = 1.7 degrees) and side jump (RMS = 1.5 degrees) movements. Between subjects, 2D-Cam and 3D data correlated well for the side step (r2 = 0.58) and side jump (r2 = 0.64). Within subjects, 2D-Cam and 3D data correlated moderately for the side step (r2 = 0.25 (0.19)) and side jump (r2 = 0.36 (0.27)). CONCLUSIONS: The 2D-Cam method can be used to screen for excessive valgus in elite basketball players, particularly for movements occurring primarily in the frontal plane. This method may also be a useful training evaluation tool when large reductions in dynamic valgus motions are required.

Effect of gender on lower extremity kinematics during rapid direction changes: an integrated analysis of three sports movements.

Anterior cruciate ligament (ACL) injury is a common sports injury, particularly in females. Gender differences in knee kinematics have been observed for specific movements, but there is limited information on how these findings relate to other joints and other movements. Here we present an integrated analysis of hip, knee and ankle kinematics across three movements linked to non-contact ACL injury. It was hypothesised that there are gender differences in lower extremity kinematics, which are consistent across sports movements. Ten female and ten male NCAA basketball players had three-dimensional hip, knee and ankle kinematics quantified during the stance phase of sidestep, sidejump and shuttle-run tasks. For each joint angle, initial value at contact, peak value and between-trial variability was obtained and submitted to a two-way mixed design ANOVA (gender and movement), with movement condition treated as a repeated measure. Females had higher peak knee valgus and lower peak hip and knee flexion, with the same gender differences also existing at the beginning of stance (p<0.05). Peak valgus measures were highly correlated between movements, but not to static valgus alignment. Kinematic differences demonstrated by females for the sports movements studied, and in particular knee valgus, may explain their increased risk of ACL injury. These differences appear to stem largely from subject-specific neuromuscular mechanisms across movements, suggesting that prevention via neuromuscular training is possible.

Development and validation of a 3-D model to predict knee joint loading during dynamic movement.

The purpose of this study was to develop a subject-specific 3-D model of the lower extremity to predict neuromuscular control effects on 3-D knee joint loading during movements that can potentially cause injury to the anterior cruciate ligament (ACL) in the knee. The simulation consisted of a forward dynamic 3-D musculoskeletal model of the lower extremity, scaled to represent a specific subject. Inputs of the model were the initial position and velocity of the skeletal elements, and the muscle stimulation patterns. Outputs of the model were movement and ground reaction forces, as well as resultant 3-D forces and moments acting across the knee joint. An optimization method was established to find muscle stimulation patterns that best reproduced the subject's movement and ground reaction forces during a sidestepping task. The optimized model produced movements and forces that were generally within one standard deviation of the measured subject data. Resultant knee joint loading variables extracted from the optimized model were comparable to those reported in the literature. The ability of the model to successfully predict the subject's response to altered initial conditions was quantified and found acceptable for use of the model to investigate the effect of altered neuromuscular control on knee joint loading during sidestepping. Monte Carlo simulations (N = 100,000) using randomly perturbed initial kinematic conditions, based on the subject's variability, resulted in peak anterior force, valgus torque and internal torque values of 378 N, 94 Nm and 71 Nm, respectively, large enough to cause ACL rupture. We conclude that the procedures described in this paper were successful in creating valid simulations of normal movement, and in simulating injuries that are caused by perturbed neuromuscular control.

Knee joint kinematics during the sidestep cutting maneuver: potential for injury in women.

PURPOSE: There is a paucity of data describing female lower limb biomechanics during "high risk" movements linked to noncontact ACL injury. This study compared, across gender, knee kinematics associated with sidestepping maneuvers to provide insight into why women display a significantly higher incidence of this injury than do men. METHODS: Thirty participants (16 men, 14 women) had bilateral knee joint kinematic data recorded while sidestepping. A custom software package (JTMOTION) quantified maximum, minimum, and range of motion during stance for each of the three clinical knee joint rotations (flexion/extension, adduction/abduction and external/internal rotation) over 20 (leg x condition x trial (5)) trials. RESULTS: Gender differences possessed limited clinical significance with all maximum values well within safe ranges of knee motion. Women did, however, display increased intertrial variability for axial rotation patterns during cutting compared with men. This variability was thought to be unaffected by gender, with experience level found statistically (P < 0.01) to be the major determinant of knee kinematic variability during sidestepping. Hence, the level of exposure to sidestep cutting may have a large impact on the subsequent risk of ACL injury when when one performs these maneuvers. CONCLUSIONS: Gender differences in knee motions during cutting did not contribute to the increased risk of noncontact ACL injury in women compared with men. The reasons for this increased incidence, therefore, remain unclear. The potential relationship between gender and other parameters linked to ACL injury such as joint geometry, ligament morphology, and physical conditioning requires further investigation.

A quantitative analysis of knee joint kinematics during the sidestep cutting maneuver. Implications for non-contact anterior cruciate ligament injury.

This study accurately quantifies the knee joint kinematics associated with sidestep cutting maneuvers in vivo. These data were subsequently evaluated to determine the relationship between sidestep cutting and non-contact anterior cruciate ligament (ACL) injury. Sixteen male subjects, proficient in the sidestep cutting maneuver, had knee joint kinematic data recorded during the stance phase of straight line running and sidestep cutting. Cutting speeds (5.5 msec-1 to 7.0 msec-1) and angles (30 degrees to 55 degrees) were chosen to reflect the sporting context. All subjects underwent medical screening prior to testing to ensure data represented joint biomechanics of healthy, ACL intact individuals. The temporal three dimensional positions of externally mounted (skin) markers were submitted to a custom software package (JTMOTION), which described in clinically meaningful terms, movements for the three rotational degrees of freedom at the knee joint. While mean patterns of motion for the three clinical knee rotations compared favorably between running and cutting data, sidestepping induced significantly (p < 0.01) greater maximum knee joint rotations during stance. Knee joint rotational ranges were also found to be significantly (p < 0.01) larger during cutting when compared to running. Increases in knee joint kinematics during cutting however, were not of a great enough magnitude to alone elicit spontaneous non-contact ACL injury, falling well within "safe" ranges of knee motion. Significant increases in inter-trial variability for the three rotations were observed in some subjects for sidestepping compared to running. It was concluded that a lack of consistency in knee joint biomechanics between cutting maneuvers increased the risk of ACL injury with the performance of an abnormal and potentially hazardous sidestep being more likely. The risk of non-contact ACL injury during cutting maneuvers was suggested to increase further when an individual displayed these "atypical" joint biomechanics in conjunction with specific joint structures, levels of experience and conditioning, and ligament morphologies.