Modification of Knee Flexion Angle Has Patient-Specific Effects on Anterior Cruciate Ligament Injury Risk Factors During Jump Landing
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The incidence of anterior cruciate ligament (ACL) injuries may be decreased through the use of intervention programs that focus on increasing the knee flexion angle during jump landing, which decreases strain on the ACL.To investigate whether intervention training designed to change the knee flexion angle during landing causes secondary changes in other known measures associated with the risk of ACL injuries and to examine the time points when these secondary measures change.Controlled laboratory study.A total of 39 healthy recreational athletes performed a volleyball block jump task in an instrumented gait laboratory. The participants first completed the jumps without any modification to their normal landing technique. They were then given oral instruction to land softly and to increase their knee flexion angle during landing. Lower body kinematics and kinetics were measured before and after the modification using an optoelectronic motion capture system.The knee flexion angle after the modification significantly increased from 11.2° to 15.2° at initial contact and from 67.8° to 100.7° at maximum flexion, and the time between initial contact and maximum flexion increased from 177.4 to 399.4 milliseconds. The flexion modification produced a substantial reduction in vertical ground-reaction force (243.1 to 187.8 %BW) with a concomitant reduction in the maximum flexion moment. Interestingly, the flexion modification only affected the abduction angle and abduction moment for the group of participants that landed in an initial adducted position before the modification and had no significant effect on the group that landed in an abducted position.Increasing the knee flexion angle during jump landing may be an effective intervention to improve knee biomechanical risk factors associated with an ACL injury. However, the fact that the flexion modification only influenced critical risk factors (the abduction angle and abduction moment) in participants who initially landed in an adducted position suggests that the selection of interventions to prevent ACL injuries should account for patient-specific characteristics.The study helps elucidate how increasing the knee flexion angle affects lower body biomechanics and provided evidence for the need to introduce patient-specific strategies for preventing ACL injuries.Keywords:
Knee flexion
ACL injury
Ground reaction force
ACL injury
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1578 Anterior cruciate ligament (ACL) injuries occur relatively more frequently in female athletes than in male athletes. Recently, altered landing techniques (less knee flexion angle) in female athletes have been reported to be associated with an increase in ACL loading. However, the mechanism(s) responsible for ACL injuries and sex differences in landing techniques remain unclear. PURPOSE: To compare the kinetics and kinematics of females with those of males during two landing movements: vertical jump (VJ) and horizontal jump (HJ). METHODS: Kinetic and kinematic data were recorded during landing by 12 male and 11 female college students. Initial and peak joint angles of hip, knee, and ankle in a sagittal plane, and the time to reach peak knee flexion were determined from the kinematic data. Peak values for hip, knee, and ankle moments and powers, ground reaction force, and anterior tibial shear force were determined and normalized to body mass. Repeated measures ANOVA was used to identify sex related differences. RESULTS: During VJ, time to reach maximum knee flexion was lower for females (183 ± 36ms vs. 224 ± 36ms, p = 0.01), whereas other variables did not differ. During HJ, knee moments (3.10 ± 1.13Nm vs. 2.25 ± 0.57Nm, p = 0.04), knee power (−23 ± 6.8W/kg vs. −16 ± 6.8W/kg, p = 0.03) and time to reach peak knee flexion (female: 187 ± 33ms vs. 217 ± 35ms, p = 0.05) were significantly greater in males. CONCLUSIONS: Males and females in this study exhibited similar landing kinematics, suggesting that the kinematics per se are not responsible for the increased ACL injury rate of females. However, our results suggest that altered energy dissipation in females, as demonstrated by different time to reach maximum knee flexion, may represent a possible mechanism for increased ACL injury rates in female athletes.
Ground reaction force
Knee flexion
Ankle dorsiflexion
Force platform
ACL injury
Biomechanics
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Backward jump-landing during sports performance will result in dynamic postural instability with a greater risk of injury, and most research studies have focused on forward landing. Differences in kinematic temporal characteristics between single-leg and double-leg backward jump-landing are seldom researched and understood. The purpose of this study was to compare and analyze lower extremity kinematic differences throughout the landing phases of forward and backward jumping using single-leg and double-leg landings (FS and BS, FD and BD). Kinematic data were collected during the landing phases of FS and BS, FD and BD in 45 participants. Through statistical parametric mapping (SPM) analysis, we found that the BS showed smaller hip and knee flexion and greater vertical ground reactive force (VGRF) than the FS during 0–37.42% (p = 0.031), 16.07–32.11% (p = 0.045), and 23.03–17.32% (p = 0.041) landing phases. The BD showed smaller hip and knee flexion than the FD during 0–20.66% (p = 0.047) and 0–100% (p < 0.001) landing phases. Most differences appeared within a time frame during the landing phase at 30–50 ms in which non-contact anterior cruciate ligament (ACL) injuries are thought to occur and are consistent with the identification of risk in biomechanical analysis. A landing strategy that consciously increases the knee and hip flexion angles during backward landing should be considered for people as a measure to avoid injury during the performance of this type of physical activity.
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1578 Anterior cruciate ligament (ACL) injuries occur relatively more frequently in female athletes than in male athletes. Recently, altered landing techniques (less knee flexion angle) in female athletes have been reported to be associated with an increase in ACL loading. However, the mechanism(s) responsible for ACL injuries and sex differences in landing techniques remain unclear. PURPOSE: To compare the kinetics and kinematics of females with those of males during two landing movements: vertical jump (VJ) and horizontal jump (HJ). METHODS: Kinetic and kinematic data were recorded during landing by 12 male and 11 female college students. Initial and peak joint angles of hip, knee, and ankle in a sagittal plane, and the time to reach peak knee flexion were determined from the kinematic data. Peak values for hip, knee, and ankle moments and powers, ground reaction force, and anterior tibial shear force were determined and normalized to body mass. Repeated measures ANOVA was used to identify sex related differences. RESULTS: During VJ, time to reach maximum knee flexion was lower for females (183 ± 36ms vs. 224 ± 36ms, p = 0.01), whereas other variables did not differ. During HJ, knee moments (3.10 ± 1.13Nm vs. 2.25 ± 0.57Nm, p = 0.04), knee power (−23 ± 6.8W/kg vs. −16 ± 6.8W/kg, p = 0.03) and time to reach peak knee flexion (female: 187 ± 33ms vs. 217 ± 35ms, p = 0.05) were significantly greater in males. CONCLUSIONS: Males and females in this study exhibited similar landing kinematics, suggesting that the kinematics per se are not responsible for the increased ACL injury rate of females. However, our results suggest that altered energy dissipation in females, as demonstrated by different time to reach maximum knee flexion, may represent a possible mechanism for increased ACL injury rates in female athletes.
Ground reaction force
Knee flexion
Ankle dorsiflexion
Force platform
ACL injury
Biomechanics
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Anterior cruciate ligament (ACL) deficient and reconstructed knees display altered biomechanics during gait. Identifying significant gait changes is important for understanding normal and ACL function and is typically performed by statistical approaches. This paper focuses on the development of an explainable machine learning (ML) empowered methodology to: (i) identify important gait kinematic, kinetic parameters and quantify their contribution in the diagnosis of ACL injury and (ii) investigate the differences in sagittal plane kinematics and kinetics of the gait cycle between ACL deficient, ACL reconstructed and healthy individuals. For this aim, an extensive experimental setup was designed in which three-dimensional ground reaction forces and sagittal plane kinematic as well as kinetic parameters were collected from 151 subjects. The effectiveness of the proposed methodology was evaluated using a comparative analysis with eight well-known classifiers. Support Vector Machines were proved to be the best performing model (accuracy of 94.95%) on a group of 21 selected biomechanical parameters. Neural Networks accomplished the second best performance (92.89%). A state-of-the-art explainability analysis based on SHapley Additive exPlanations (SHAP) and conventional statistical analysis were then employed to quantify the contribution of the input biomechanical parameters in the diagnosis of ACL injury. Features, that would have been neglected by the traditional statistical analysis, were identified as contributing parameters having significant impact on the ML model's output for ACL injury during gait.
Biomechanics
ACL injury
Ground reaction force
Gait cycle
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Anterolateral ligament
ACL injury
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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.
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ACL injury
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It has been suggested that noncontact anterior cruciate ligament injury commonly occurs during sports requiring acute deceleration or landing motion and that female athletes are more likely to sustain the injury than male athletes. The purpose of this study was to make task-to-task and male-female comparisons of knee kinematics and kinetics in several athletic activities. Three-dimensional knee kinematics and kinetics were investigated in 20 recreational athletes (10 males, 10 females) while performing hopping, cutting, turning, and sidestep and running (sharp deceleration associated with a change of direction). Knee kinematics and kinetics were compared among the four athletic tasks and between sexes. Subjects exhibited significantly lower peak flexion angle and higher peak extension moment in hopping compared with other activities ( P < .05). In the frontal plane, peak abduction angle and peak adduction moment in cutting, turning, and sidestep and running were significantly greater compared with hopping ( P < .05). No differences in knee kinematics and kinetics were apparent between male and female subjects. Recreational athletes exhibited different knee kinematics and kinetics in the four athletic motions, particularly in the sagittal and frontal planes. Male and female subjects demonstrated similar knee motions during the four athletic activities.
Knee flexion
Biomechanics
ACL injury
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The incidence of anterior cruciate ligament (ACL) injuries may be decreased through the use of intervention programs that focus on increasing the knee flexion angle during jump landing, which decreases strain on the ACL.To investigate whether intervention training designed to change the knee flexion angle during landing causes secondary changes in other known measures associated with the risk of ACL injuries and to examine the time points when these secondary measures change.Controlled laboratory study.A total of 39 healthy recreational athletes performed a volleyball block jump task in an instrumented gait laboratory. The participants first completed the jumps without any modification to their normal landing technique. They were then given oral instruction to land softly and to increase their knee flexion angle during landing. Lower body kinematics and kinetics were measured before and after the modification using an optoelectronic motion capture system.The knee flexion angle after the modification significantly increased from 11.2° to 15.2° at initial contact and from 67.8° to 100.7° at maximum flexion, and the time between initial contact and maximum flexion increased from 177.4 to 399.4 milliseconds. The flexion modification produced a substantial reduction in vertical ground-reaction force (243.1 to 187.8 %BW) with a concomitant reduction in the maximum flexion moment. Interestingly, the flexion modification only affected the abduction angle and abduction moment for the group of participants that landed in an initial adducted position before the modification and had no significant effect on the group that landed in an abducted position.Increasing the knee flexion angle during jump landing may be an effective intervention to improve knee biomechanical risk factors associated with an ACL injury. However, the fact that the flexion modification only influenced critical risk factors (the abduction angle and abduction moment) in participants who initially landed in an adducted position suggests that the selection of interventions to prevent ACL injuries should account for patient-specific characteristics.The study helps elucidate how increasing the knee flexion angle affects lower body biomechanics and provided evidence for the need to introduce patient-specific strategies for preventing ACL injuries.
Knee flexion
ACL injury
Ground reaction force
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Citations (34)
In healthy individuals, maximum vertical ground reaction force (MVGRF) remains close to constant during constant velocity running, despite variation in stiffness of the surface underfoot. Because the anterior cruciate ligament (ACL) possesses mechanoreceptors that influence recruitment of knee muscles, it may play a role in regulation of lower limb force output. This study was designed to examine the effect of recent ACL reconstruction on MVGRF in running. Seven patients who were 5-13 weeks post-ACL reconstruction and 7 healthy participants ran for 60 seconds in shoes modified with hard and with soft 1-cm outsoles. The MVGRF during running was measured for the ACL reconstructed and nonsurgical limbs of patients and limbs of healthy participants. The difference in MVGRF between running in hard and soft shoes was significantly greater in ACL reconstructed limbs than nonsurgical limbs (p = 0.003) and compared to limbs of healthy participants (p = 0.001). In contrast, a difference in MVGRF between shoes was not found between patients' nonsurgical limbs and those of healthy participants. A lack of mechanoreceptive feedback from the ACL graft may be among the factors explaining the difference between the ACL reconstructed limbs and the other two limb conditions.
Ground reaction force
ACL injury
Knee flexion
Biomechanics
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