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Knee injuries are common in jumping athletes; modifying jump strategy may impact loads placed on the body and reduce injury risk. The purpose of this study was to determine if modifying strategy in a saut de chat leap to focus on height would decrease sagittal plane knee loading. Biomechanical data were collected while 28 dancers performed saut de chat leaps with instructions to jump far (FAR) or jump high (UP). In the UP condition, there was greater vertical GRF and less braking GRF. Also in UP, lower extremity contact angle was greater (71.3 ± 2.9º FAR; 75.8 ± 3.3º UP; p = 0.0178), peak knee extensor moment was greater (2.8 ± 0.7 Nm FAR; 3.2 ± 0.8 Nm UP; p = 0.01), and peak ankle plantar flexor moment was lower (3.19 ± 0.4 Nm FAR; 2.94 ± 0.4 Nm UP; p < 0.01). A more acute LECA was related to greater braking force and braking force was related to greater knee extensor moments. Despite these relationships, we observed greater knee extensor moments in UP. While the relationship among these whole-body variables and knee joint loading exists, it may not be the primary factor driving load distribution during dance leap landings.

Biomechanical studies consistently report smaller knee extensor moments in the surgical limb during loading response (LR) of gait following ACL reconstruction (ACLr). However, this reduction in knee loading is quantified by net joint moments (NJM). As a result, in the presence of greater hamstring activity, the true contribution from the knee extensors may not be reduced. The purpose of this study is to compare hamstring activity and strength and knee joint moments between individuals post-ACLr and controls. Eighteen individuals 3 months post-ACLr and matched controls walked and net knee extensor moment peak and impulse and hamstring activity were identified during LR, as well as maximal hamstring strength. A hybrid musculoskeletal model estimated knee flexor moments from joint kinematics and hamstring electromyography. Flexor moments (SIMM) were scaled based on strength. Knee extensor moments were estimated from the sum of the net knee moment and estimated knee flexor moment; estimated extensor moment peaks and impulse were calculated during LR. Repeated measures analysis of variance compared groups and limbs. Smaller net knee extensor moment and greater hamstring activity, as well as deficits in maximal hamstring strength, were observed in the surgical limb (all p < 0.05). When accounting for the torque-producing capabilities of the knee flexors, estimated knee extensor moment peak and impulse were smaller in the surgical limb. These findings suggest that net knee moments accurately reflect smaller knee extensor loading post-ACLr. Statement of Clinical Significance: Rehabilitation programs should target increasing knee extensor loading to restore gait mechanics during early rehabilitation. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:378-386, 2020., (© 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.)

Background: Clinically, normalization of gait following anterior cruciate ligament reconstruction (ACLr) is defined as the absence of observable deviations. However, biomechanical studies report altered knee mechanics during loading response (LR); a time of double limb support and weight transfer between limbs. It is conceivable that subtle adjustments in whole body mechanics, including center of mass (COM) velocity and ground reaction force (GRF) peaks and timing, are present., Research Question: The purpose was to compare limb and whole body mechanics during LR of gait in the surgical and non-surgical limbs post-ACLr., Methods: Anterior and vertical COM velocity at initial contact; knee flexion range of motion, peak knee extensor moment, peak vertical and posterior GRF, minimum vertical COM position and maximum anterior and vertical COM velocity during LR were identified for twenty individuals 112 ± 17 days post-ACLr without observable gait deficits. To assess differences in timing of COM variables, coupling angles (vector coding) were calculated for multidirectional coordination of vertical and anteroposterior COM velocities and GRFs and categorized as in-phase, anti-phase, vertical phase, or anteroposterior phase coordination. Paired t-tests compared peaks between limbs; non-parametric Wilcoxon signed-rank tests compared coordination pattern frequency., Results: Less knee range of motion (5.6 °), 30% smaller knee extensor moment, 11% smaller posterior GRF, and slower anterior COM velocity at initial contact (2%) and peak during LR (1.3%; all p < 0.05) were observed in the surgical compared to the non-surgical limb. For COM velocity coordination, lesser anti-phase (7.38%) and greater in-phase coordination (2.88%) were observed in the surgical limb. For GRF coordination, less in-phase coordination (1.94%) was observed in the surgical limb., Significance: Differences in coordination patterns, suggest that individuals post-ACLr make subtle adjustments in timing of whole body mechanics; particularly in COM velocity during gait. These adjustments are consistent with reduced sagittal plane loading in the surgical knee., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: Altered gait mechanics following anterior cruciate ligament reconstruction (ACLr) are commonly reported in the surgical limb 2-3 months post-surgery when normalization of gait is expected clinically. Specifically, deficits in knee extensor moment during loading response of gait are found to persist long-term; however, the mechanisms by which individuals reduce sagittal plane knee loading during gait are not well understood., Research Question: This study investigated between limb asymmetries in knee flexion range of motion, shank angular velocity, and ground reaction forces to determine the strongest predictor of knee extensor moment asymmetries during gait., Methods: Thirty individuals 108 ± 17 days post-ACLr performed walking gait at a self-selected speed and peak knee extensor moment, peak vertical and posterior ground reaction force, and peak anterior shank angular velocity were identified during loading response. Paired t-tests compared limbs; Pearson's correlations determined associations between variables in surgical and non-surgical limbs; and stepwise linear regression determined the best predictor of knee extensor moment asymmetries during gait., Results: Reduced vertical and posterior ground reaction forces and shank angular velocity were strongly associated with reduced knee extensor moment in both limbs (r = 0.499-0.917, p < 0.005). Less knee flexion range of motion was associated with reduced knee moment in the surgical limb (r = 0.358, p < 0.05). Additionally, asymmetries in posterior ground reaction force and knee flexion range of motion predicted asymmetries in knee extensor moment (R2 = 0.473, p < 0.001)., Significance: Modulation of kinetics and kinematics contribute to decreases in knee extensor moments during gait and provide direction for targeted interventions to restore gait mechanics., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background Decreased extensor moments in the surgical knee during bilateral squats can persist beyond 1 year following anterior cruciate ligament reconstruction (ACLR). This is accomplished using interlimb and intralimb compensations. Objectives This study sought to assess loading during squatting longitudinally, 3 and 5 months post ACLR, and to determine the extent to which interlimb and intralimb compensations contribute to reduced knee extensor moments. Methods In this controlled, longitudinal laboratory study, 11 individuals (4 male) underwent 3-D motion analysis of a squat at 3 and 5 months post ACLR. A repeated-measures multivariate analysis of variance (limb by time) assessed differences in peak knee and hip flexion angles, knee extensor moment, vertical ground reaction force, and hip-to-knee extensor moment ratio. Stepwise linear regression analysis was used to determine the contribution of interlimb (between-limb vertical ground reaction force ratio) and intralimb (within-surgical-limb hip-to-knee moment ratio) compensations to the between-limb knee extensor moment ratio. Results A significant effect of limb was observed for knee flexion angle, knee extensor moment, vertical ground reaction force, and hip-to-knee extensor moment ratio, while a significant effect of time was observed for knee extensor moment and hip-to-knee extensor moment ratio. At 3 months, the vertical ground reaction force ratio and hip-to-knee extensor moment ratio predicted the knee extensor moment ratio (R 2 = 0.854, P<.001). At 5 months, the hip-to-knee extensor moment ratio predicted the knee extensor moment ratio (R 2 = 0.584, P = .006). Conclusion Individuals used interlimb and intralimb compensations to reduce the knee extensor moment of the surgical limb at 3 months post ACLR. Similar reductions in the knee extensor moment at 5 months were accomplished with only intralimb compensations. J Orthop Sports Phys Ther 2018;48(9):713-718. Epub 12 Jun 2018. https://doi.org/10.2519/jospt.2018.7977.

Study Design Controlled laboratory study, cross-sectional. Background Well-documented deficits in sagittal plane knee loading during dynamic tasks indicate that individuals limit the magnitude of knee loading following anterior cruciate ligament reconstruction (ACLR). It is unknown how these individuals modulate the speed of knee flexion during loading, which is particularly important as they progress to running during rehabilitation. Objective To investigate how individuals following ACLR perform dynamic knee loading tasks compared to healthy controls. Methods Two groups of recreationally active individuals participated: 15 healthy controls and 15 individuals post-ACLR (ACLR group). Participants performed 3 trials of overground running and a single-limb loading (SLL) task. Sagittal plane range of motion, peak knee extensor moment, peak knee flexion angular velocity, peak knee power absorption, and rate of knee extensor moment were calculated during deceleration. A mixed-factor multivariate analysis of variance was performed to compare differences in variables between groups (ACLR and control), limbs (within ACLR), and tasks (within control). Results Knee power absorption, knee flexion angular velocity, and rate of knee extensor moment were lower in reconstructed limbs (for the SLL task: 5.6 W/kg, 325.8°/s, and 10.5 Nm/kg/s, respectively; for running: 11.8 W/kg, 421.4°/s, and 38.2 Nm/kg/s, respectively) compared to nonsurgical limbs (for the SLL task: 9.7 W/kg, 432.0°/s, and 19.1 Nm/kg/s, respectively; for running: 18.8 W/kg, 494.1°/s, and 72.8 Nm/kg/s, respectively) during both tasks (P<.001). The magnitudes of between-limb differences in knee flexion angular velocity were similar in both tasks. Conclusion Despite lower loading demands during SLL, individuals post-ACLR exhibit deficits in knee dynamics during SLL and running, suggesting an inability or reluctance to dynamically accommodate forces at the knee when progressing to running in rehabilitation. J Orthop Sports Phys Ther 2017;47(6):411-419. doi:10.2519/jospt.2017.6912.

Limitations in the ability to identify knee extensor loading deficits during gait in individuals following anterior cruciate ligament reconstruction (ACLr) may underlie their persistence. A recent study suggested that shank angular velocity, directly output from inertial sensors, differed during gait between individuals post-ACLr and controls. However, it is not clear if this kinematic variable relates to knee moments calculated using joint kinematics and ground reaction forces. Heel rocker mechanics during loading response of gait, characterized by rapid shank rotation, require knee extensor control. Measures of shank angular velocity may be reflective of knee moments. This study investigated the relationship between shank angular velocity and knee extensor moment during gait in individuals (n=19) 96.7±16.8days post-ACLr. Gait was assessed concurrently using inertial sensors and a marker-based motion system with force platforms. Peak shank angular velocity and knee extensor moment were strongly correlated (r=0.75, p<0.001) and between limb ratios of angular velocity predicted between limb ratios of extensor moment (r(2)=0.57, p<0.001) in the absence of between limb differences in spatiotemporal gait parameters. The strength of these relationships indicate that shank kinematic data offer meaningful information regarding knee loading and provide a potential alternative to full motion analysis systems for identification of altered knee loading following ACLr., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Background: Normalization of gait is expected 8-12 weeks after anterior cruciate ligament reconstruction and is a criterion for progression to running. Long-term persistence of sagittal knee loading deficits suggests that early goals are not met. Magnitude and progression of deficits in gait during this time and their relationship to deficits in running are not known., Methods: 12 individuals status-post reconstruction (5 males) underwent 3-dimensional motion analysis of gait after surgery: one (T1) and three (T2) months and at initiation of running (T3); and running T3. Repeated measures ANOVAs (limb × time) assessed differences in knee flexion, extensor moment impulse and negative work in gait; paired t-tests compared limbs during running; and Pearson's correlations determined associations between limb ratios (moment and work) in gait and running., Findings: Less flexion (-4.4 (0.63) degrees; mean (SE)), 35% smaller extensor moment (-0.15 (0.006) Nm∗s/kg) and 47% less work (-0.03 (0.008) J/kg) were observed in the surgical knee during gait across time. Moment and work were 1.7 (-0.1 (0.03) Nm∗s/kg) and 1.6 times greater (-0.23 (0.047) J/kg) in non-surgical knee during running. Moment and work limb asymmetries correlated across time during gait (r=0.778-0.929, P<0.001) and to asymmetries during running., Interpretation: Limb asymmetries in knee loading present one month after reconstruction persist 4 months post-reconstruction. Correlations between limb asymmetries during gait across time and to running suggest that early gait behaviors relate to longer-term loading. Greater attention should be placed on early gait training., (Copyright © 2015. Published by Elsevier Ltd.)

Objective: To compare frontal plane knee moments, and kinematics and kinetics associated with knee valgus moments between cutting to 45 and 110 degrees, and to determine the predictive value of kinematics and ground reaction forces (GRFs) on knee valgus moments when cutting to these angles. Also, to determine whether sex differences exist in kinematics and kinetics when cutting to 45 and 110 degrees., Design: Cross-sectional study., Setting: Laboratory setting., Participants: Forty-five (20 females) healthy young adult soccer athletes aged 16 to 23 years., Assessment of Risk Factors: Kinematic and kinetic variables were compared between randomly cued side-step cutting maneuvers to 45 and 110 degrees. Predictors of knee valgus moment were determined for each task., Main Outcome Measures: Kinematic variables: knee valgus angle, hip abduction, and internal rotation angles. Kinetic variables: vertical, posterior, and lateral GRFs, and knee valgus moment., Results: Knee valgus moments were greater when cutting to 110 degrees compared with 45 degrees, and females exhibited greater moments than males. Vertical and lateral GRFs, hip internal rotation angle, and knee valgus angle explained 63% of the variance in knee valgus moment during cutting to 45 degrees. During cutting to 110 degrees, posterior GRF, hip internal rotation angle, and knee valgus angle explained 41% of the variance in knee valgus moment., Conclusions: Cutting tasks with larger redirection demands result in greater knee valgus moments. Similar factors, including shear GRFs, hip internal rotation, and knee valgus position contribute to knee valgus loading during cuts performed to smaller (45 degrees) and larger (110 degrees) angles., Clinical Relevance: Reducing vertical and shear GRFs during cutting maneuvers may reduce knee valgus moments and thereby potentially reduce risk for anterior cruciate ligament injury.

Cutting is necessary for participation in multidirectional sports but is also associated with non-contact ACL injury. Whole body demands of deceleration and redirection increase with greater cut angles. However, it is not known how these demands relate to differences in joint and segmental mechanics. Understanding the relationship between whole body and joint mechanics necessary for cutting and those related to risk for injury is important for the development of injury prevention training programs. The purpose of this study is to determine how joint and segmental mechanics change to meet increasing deceleration and redirection demands during cutting. Lower limb and trunk kinematics and kinetics were evaluated during the execution of two sidestep cutting maneuvers (to 45 and 90 degrees) in twenty-five healthy soccer players. A two-way multivariate analysis of covariance (MANCOVA) determined that differences existed between task directions but not sexes when considering all dependent variables and covarying for approach velocity (α≤0.05). Post hoc analyses revealed that the larger deceleration and redirection demands of the 90-degree cut did not translate into larger angles, moments and power across all lower extremity joints. In the sagittal plane, the knee appeared to primarily accommodate the greater deceleration demands of the sharper cut. These data further suggest that the hip may play a different role during cutting to smaller and larger angles and also illustrate a pattern of engagement in the sagittal and frontal planes that has not been described previously., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Introduction: Females have been reported to have a three to five times greater incidence of noncontact anterior cruciate ligament injury when compared with their male counterparts. Previous research suggests that physical maturation is one factor that is associated with the development of potentially injurious lower extremity biomechanics in female athletes., Purpose: The study's purpose was to determine whether lower extremity biomechanics differ between male and female soccer athletes during a cutting maneuver across different stages of maturational development., Methods: One hundred fifty-six soccer players (76 males and 80 females) between the ages of 9 and 23 yr participated. Subjects were classified on the basis of maturation as prepubertal, pubertal, postpubertal, or young adult. Lower extremity kinematics, kinetics, and ground reaction forces (GRFs) were obtained during a 45° side-step cutting maneuver. Differences between sex and maturation were assessed for peak knee valgus angle, knee adductor moments, and GRFs (vertical, posterior, and lateral) during weight acceptance using a two-factor ANCOVA (controlling for approach velocity)., Results: No sex × maturation interactions were found for any variable of interest. On average, females exhibited greater knee abduction and adductor moments than males. Prepubertal athletes demonstrated greater knee adductor moments and GRFs than all other groups., Conclusions: Biomechanical differences between males and females were evident across all stages of maturation. On average, less mature athletes exhibit biomechanical patterns during cutting that may place them at greater risk for injury than their more mature counterparts.

Context: Excessive knee valgus during dynamic tasks is thought to contribute to lower extremity overuse and traumatic injuries. Clinically, assessments of frontal-plane knee motion typically include measures of the distance between the knees during landing. However, it is not clear how this clinical assessment relates to knee-abduction angle or how it is influenced by the position of the lower extremities in the transverse and frontal planes., Objective: To determine whether normalized knee separation distance (NKSD) is a predictor of knee-abduction angles and to assess the influence of lower extremity transverse-plane and frontal-plane angles on NKSD during a drop land., Design: Cross-sectional study., Setting: Motion analysis laboratory., Patients or Other Participants: Twenty-five healthy female athletes., Intervention(s): The frontal-plane distance between the 2-dimensional coordinates of markers over the greater trochanters (intertrochanteric distance), lateral femoral epicondyles (knee separation distance), and lateral malleoli (stance width) bilaterally was calculated during a drop land. The knee separation distance was normalized by intertrochanteric distance (NKSD). Concurrently, 3-dimensional lower extremity transverse-plane and frontal-plane kinematics were obtained., Main Outcome Measure(s): We assessed NKSD, stance width, and bilateral average knee and hip transverse plane and frontal-plane angles and ankle frontal-plane angles. Linear regression was used to determine the association between NKSD and bilateral average knee frontal-plane angles. Stepwise multiple regression was used to identify the best predictors of NKSD during the drop land., Results: After we controlled for stance width, NKSD explained 52% of the variance in the knee frontal-plane angle. When we took lower extremity kinematics into account, after controlling for stance width, the average hip frontal-plane angle was the best predictor of NKSD, explaining 97% of the variance., Conclusions: Although NKSD is a predictor of knee-abduction angle, frontal-plane hip angle and stance width are strongly related to NKSD. Caution must be taken when interpreting NKSD as knee abduction.

Background: It has been proposed that female athletes who limit knee and hip flexion during athletic tasks rely more on the passive restraints in the frontal plane to deceleration their body center of mass. This biomechanical pattern is thought to increase the risk for anterior cruciate ligament injury. To date, the relationship between sagittal plane kinematics and frontal plane knee motion and moments has not been explored., Methods: Subjects consisted of 58 female club soccer players (age range: 11-20 years) with no history of knee injury. Kinematics, ground reaction forces, and surface electromyography were collected while each subject performed a drop landing task. Subjects were divided into two groups based on combined sagittal plane knee and hip flexion angles during the deceleration phase of landing (high flexion and low flexion)., Findings: Subjects in the low flexion group demonstrated increased knee valgus angles (P=0.02, effect size 0.27), increased knee adductor moments (P=0.03, effect size 0.24), decreased energy absorption at the knee and hip (P=0.02, effect size 0.25; and P<0.001, effect size 0.59), and increased vastus lateralis EMG when compared to subjects in the high flexion group (P=0.005, effect size 0.35)., Interpretation: Female athletes with limited sagittal plane motion during landing exhibit a biomechanical profile that may put these individuals at greater risk for anterior cruciate ligament injury., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

Introduction: Changes in knee mechanics immediately after a fatiguing bout of exercise are thought to place an individual at a greater risk for anterior cruciate ligament (ACL) injury. However, the recovery time required to restore normal knee kinetics and kinematics after fatigue has not been established., Purpose: The purpose of this study was to examine knee mechanics during side-step cutting immediately after a fatigue protocol and after 20 and 40 min of rest., Methods: Knee kinematics (eight-camera system Vicon 612; Oxford Metrics, Oxford, United Kingdom) and kinetics (AMTI force platform; AMTI, Newton, MA) of 15 female recreational athletes were recorded during a side-step cutting task. Data were obtained at four different time points: 1) before a fatigue protocol, 2) immediately after the fatigue protocol, 3) 20 min after the fatigue protocol, and 4) 40 min after the fatigue protocol. Peak knee joint angles and knee joint moments in the sagittal, frontal, and transverse planes were identified during the deceleration phase of the cutting task. One-way ANOVA with repeated measures were used to compare variables among the four time points., Results: Peak internal knee adductor moments (external knee valgus moments) and peak knee internal rotation angles were significantly greater after fatigue and remained elevated at 20 and 40 min after fatigue. Peak knee abduction (valgus) angles immediately after the fatigue protocol were significantly greater but returned to prefatigue levels after 20 min of rest. The fatigue protocol had no influence on any other of the variables examined., Conclusions: Fatigue resulted in changes in knee mechanics that are thought to be associated with ACL injury. Forty minutes of recovery was not sufficient in restoring knee mechanics to prefatigue levels.

Study Design: Controlled laboratory study using a cross-sectional, single testing session., Objective: To determine the association between frontal plane knee excursion during a drop land task and measures of hip strength, and ankle and hip range of motion., Background: Assessment of frontal plane knee excursion during a drop land task has been advocated as a means to screen for potentially injurious lower extremity movement patterns. Accordingly, an understanding of the physical characteristics associated with the magnitude of frontal plane knee excursion could assist clinicians in developing interventions and prevention strategies to minimize injury risk., Methods and Measures: Thirty-nine female high school soccer players (mean +/- SD age, 15.5 +/- 1.0 years; height, 162.2 +/- 5.3 cm; body mass, 56.8 +/- 6.7 kg) participated. Isometric hip muscle strength as well as ankle and hip range of motion measurements were obtained using standard clinical procedures and a handheld dynamometer. Frontal plane knee excursion was assessed using a 6-camera motion analysis system during a drop land task. Using 3-dimensional coordinate data, maximum frontal plane knee excursion was defined as the difference between the distances of right and left lateral knee markers at initial contact and maximum knee flexion during the deceleration phase of landing. Independent variables found to be significantly correlated with frontal plane knee excursion were then entered into a stepwise multiple regression procedure to determine the best set of predictors of this motion., Results: Hip external rotation range of motion and ankle dorsiflexion range of motion were found to be negatively correlated with frontal plane knee excursion (r=-0.40, P=.005 and r=-0.27, P=.05, respectively). Together they accounted for 27% of the variance in frontal plane knee excursion (r=0.52, P=.03). No relationships between measures of hip strength and frontal plane knee excursion were found., Conclusions: Frontal plane knee excursion during a drop land task was partially attributed to available range of motion at the hip and ankle. These results suggest that range of motion of the joints proximal and distal to the knee should be considered when evaluating individuals who present with excessive frontal plane knee excursion during this task. Given that the relationship between range of motion and frontal plane knee excursion was small, other factors, including learned motor patterns, should be considered.

Background: Excessive knee valgus moments are considered a risk factor for non-contact anterior cruciate ligament injuries in female athletes, however, little is known about the biomechanical factors that contribute to this loading pattern. The purpose of this study was to compare lower extremity kinematics, foot position and ground reaction forces between female soccer players who demonstrate normal frontal plane moments at the knee with those who demonstrate excessive frontal plane moments at the knee during a cutting maneuver., Methods: Sixty-one female soccer players, 16 (2) years, participated. Three dimensional kinematics and ground reaction forces were recorded during a side-step cutting maneuver. Knee frontal plane moments were calculated with inverse dynamics equations and were used to classify subjects into normal (N=38) and excessive valgus moment (N=23) groups., Findings: Data revealed that the subjects with excessive valgus moments demonstrated an initial loading pattern that included greater laterally directed ground reaction forces (P<0.001, effect size 1.51), increased hip abduction (P=0.002, effect size 0.79), increased hip internal rotation (P=0.008, effect size 0.71) and a more internally rotated foot progression angle (P=0.04, effect size 0.55). Taken together, these variables explained 49% of the variance in peak knee valgus moment (R=.698, P<0.001)., Interpretation: These results provide insight into potentially injurious loading strategies and support the premise that interventions designed to encourage loading of the lower extremity in a more neutral alignment may work to decrease frontal plane loading at the knee.

Background: It has been suggested that gender differences in the performance of athletic maneuvers is a contributory factor with respect to the disproportionate incidence of non-contact anterior cruciate ligament injury in female athletes. The purpose of this study was to evaluate gender differences in knee joint kinematics, kinetics and muscle activation during a side-step cutting., Methods: Three-dimensional kinematics, ground reaction forces (2400 Hz) and electromyographic activity (surface electrodes) were recorded during the early deceleration phase of side-step cutting in 30 healthy collegiate soccer players (15 male, 15 female). Gender differences in knee joint kinematics, peak moments, net joint moment impulse and average muscle EMG intensity were evaluated with one-tailed t-tests., Findings: No differences in kinematics were found. However, when compared to males, females demonstrated a smaller peak knee flexor moment (1.4 (0.8) vs. 2.1 (0.8) Nm/kg, P = 0.05) and a greater knee adductor moment (0.43 (0.5) vs. 0.01 (0.3) Nm/kg, P < 0.01) during early deceleration. In addition, females displayed greater average quadriceps EMG intensity than males (191% vs. 151% maximum voluntary isometric contraction, P = 0.02)., Interpretation: In general, females experienced increased frontal plane moments and decreased sagittal plane moments during early deceleration. These differences are suggestive of an "at risk" pattern in that frontal plane support of the knee is afforded primarily by passive structures (including the anterior cruciate ligament). Furthermore, increased quadriceps activity and smaller net flexor moments may suggest less sagittal plane protection (i.e., increased tendency towards anterior tibial translation).