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Xingda Qu, Jianxin Jiang and Xinyao Hu

for preventing knee injuries. The effects of subsensory noise on knee biomechanics need to be better characterized, because it is important to clarify the mechanisms by which subsensory noise may affect ACL injury risk. Fatigue is associated with loss of proprioceptive acuity. 14 In fact, fatigue is

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Zakariya Nawasreh, David Logerstedt, Adam Marmon and Lynn Snyder-Mackler

-based, patient-reported, and knee biomechanics measures after an acute ACL rupture. The results of this study revealed that administration of perturbation training using mechanical device induces effects similar to the manual training after an acute ACL rupture. In this study, both motion analysis and clinical

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Louise M. Thoma, David C. Flanigan, Ajit M. Chaudhari, Robert A. Siston, Thomas M. Best and Laura C. Schmitt

Context:

Few objective data are available regarding strength and movement patterns in individuals with articular cartilage defects (ACDs) of the knee.

Objectives:

To test the following hypotheses: (1) The involved limb of individuals with ACDs would demonstrate lower peak knee-flexion angle, peak internal knee-extension moment, and peak vertical ground-reaction force (vGRF) than the contralateral limb and healthy controls. (2) On the involved limb of individuals with ACDs, quadriceps femoris strength would positively correlate with peak knee-flexion angle, peak internal knee-extension moment, and peak vGRF.

Design:

Cross-sectional.

Setting:

Biomechanics research laboratory.

Participants:

11 individuals with ACDs in the knee who were eligible for surgical cartilage restoration and 10 healthy controls.

Methods:

Quadriceps femoris strength was quantified as peak isometric knee-extension torque via an isokinetic dynamometer. Sagittal-plane knee kinematics and kinetics were measured during the stance phase of stair ascent with 3-dimensional motion analysis.

Main Outcome Measures:

Quadriceps strength and knee biomechanics during stair ascent were compared between the involved and contralateral limbs of participants with ACD (paired t tests) and with a control group (independent-samples t tests). Pearson correlations evaluated relationships between strength and stair-ascent biomechanics.

Results:

Lower quadriceps strength and peak internal knee-extension moments were observed in the involved limb than in the contralateral limb (P < .01) and the control group (P < .01). For the involved limb of the ACD group, quadriceps femoris strength was strongly correlated (r = .847) with involved-limb peak internal knee-extension moment and inversely correlated (r = −.635) with contralateral peak vGRF. Conclusions: Individuals with ACDs demonstrated deficits in quadriceps femoris strength with associated alterations in movement patterns during stair ascent. The results of this study are not comprehensive; further research is needed to understand the physiological characteristics, activity performance, and movement quality in this population.

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Boyi Dai, Christopher J. Sorensen, Timothy R. Derrick and Jason C. Gillette

The effects of training on biomechanical risk factors for anterior cruciate ligament (ACL) injuries have been investigated, but the effects of detraining have received little attention. The purpose of this study was to evaluate the effects of a one-month postseason break on knee biomechanics and lower extremity electromyography (EMG) during a stop-jump task. A postseason break is the phase between two seasons when no regular training routines are performed. Twelve NCAA female volleyball players participated in two stop-jump tests before and after the postseason break. Knee kinematics, kinetics, quadriceps EMG, and hamstring EMG were assessed. After one month of postseason break, the players demonstrated significantly decreased jump height, decreased initial knee flexion angle, decreased knee flexion angle at peak anterior tibial resultant force, decreased prelanding vastus lateralis EMG, and decreased prelanding biceps femoris EMG as compared with prebreak. No significant differences were observed for frontal plane biomechanics and quadriceps and hamstring landing EMG between prebreak and postbreak. Although it is still unknown whether internal ACL loading changes after a postseason break, the more extended knee movement pattern may present an increased risk factor for ACL injuries.

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Kam-Ming Mok, Eirik Klami Kristianslund and Tron Krosshaug

Knee valgus angles measured in sidestep cutting and vertical drop jumps are key variables in research on anterior cruciate ligament (ACL) injury causation. These variables are also used to quantify knee neuromuscular control and ACL injury risk. The aims of the current study were to (1) quantify the differences in the calculated knee valgus angles between 6 different thigh marker clusters, (2) investigate the trial ranking based on their knee valgus angles, and (3) investigate the influence of marker clusters on the cross-talk effect. Elite female handball and football players (n = 41) performed sidestep cutting and vertical drop jumping motions. We found systematic differences up to almost 15° of peak valgus between the marker sets in the drop jump test. The Spearman’s rank correlation coefficient varied from .505 to .974 among the 6 marker sets. In addition, the cross-talk effect varied considerably between the marker clusters. The results of the current study indicate that the choice of thigh marker cluster can have a substantial impact on the magnitude of knee valgus angle, as well as the trial ranking. A standardized thigh marker cluster, including nonanatomical landmark, is needed to minimize the variation of the measurement.

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Nathaniel A. Bates, Nathan D. Schilaty, Ryo Ueno and Timothy E. Hewett

Anterior cruciate ligament (ACL) injury videos estimate that rupture occurs within 50 milliseconds of initial contact, but are limited by imprecise timing and nondirect data acquisition. The objective of this study was to precisely quantify the timing associated with ligament strain during simulated landing and injury events. The hypotheses tested were that the timing of peak strain following initial contact would differ between ligaments and that peak strain timing would be independent of the injury-risk profile emulated during simulated landing. A mechanical impact simulator was used to perform landing simulations based on various injury-risk profiles that were applied to each specimen in a block-randomized order. The ACL and medial collateral ligament were instrumented with strain gauges that recorded continuously. The data from 35 lower-extremity specimens were included for analysis. Analysis of variance and Kruskal–Wallis tests were used to determine the differences between timing and profiles. The mean time to peak strain was 53 (24) milliseconds for the ACL and 58 (35) milliseconds for the medial collateral ligament. The time to peak ACL strain ranged from 48 to 61 milliseconds, but the timing differences were not significant between profiles. Strain timing was independent of injury-risk profile. Noncontact ACL injuries are expected to occur between 0 and 61 milliseconds after initial contact. Both ligaments reached peak strain within the same time frame.

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Shogo Uota, Anh-Dung Nguyen, Naoko Aminaka and Yohei Shimokochi

Context:

Excessive knee valgus and tibial external rotation relative to the femur during weight bearing motions, such as jump-landing, reportedly increases the risk of developing chronic knee pain, such as patellofemoral pain. Excessive deviations from normal ranges of several static lower extremity alignment measures and dynamic hip motions may also increase the risks for patellofemoral pain.

Objective:

To determine the relationship between lower extremity alignments and hip motions to frontal and transverse plane knee motions during double-leg landings.

Design:

Correlational study.

Setting:

Laboratory.

Patients or Other Participants:

69 healthy, competitive athletes (27 men, 42 women; height, 166.5 ± 9.5 cm; weight, 61.3 ± 9.9 kg; age, 20.7 ± 1.0 y) participated in this study.

Interventions:

Prone and supine hip version, quadriceps angle, and tibiofemoral angle were measured. Frontal and transverse knee and hip angles at peak knee extensor moment during landing were calculated.

Main Outcome Measures:

2 separate stepwise multiple regression analyses were conducted to predict frontal and transverse plane knee motions using 4 static lower extremity alignment measures and hip motions.

Results:

Greater hip adduction and prone hip anteversion, and lesser hip internal rotation and supine hip anteversion, were related to greater knee valgus motions (R 2 = .475, P < .01). Greater hip adduction was related to greater knee external rotation (R 2 = .205, P < .01).

Conclusions:

Some targeted static lower extremity alignments and hip motions are associated with frontal and transverse knee motions. However, stronger relationships of hip motions with knee motions than static lower extremity alignments provided evidence that improving hip movements may help improve patellofemoral pain in those with lower extremity malalignments.

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Aiko Sakurai, Kengo Harato, Yutaro Morishige, Shu Kobayashi, Yasuo Niki and Takeo Nagura

concluded that risk factor was laterally flexed the trunk in the frontal plane toward the side of the injured knee without altering the alignment of the feet. On the other hand, toe direction is known as a critical factor affecting knee biomechanics during various movements. 18 – 21 Tran et al 21

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Miriam Klous, Erich Müller and Hermann Schwameder

Limited data exists on knee biomechanics in alpine ski turns despite the high rate of injuries associated with this maneuver. The purpose of the current study was to compare knee joint loading between a carved and a skidded ski turn and between the inner and outer leg. Kinetic data were collected using Kistler mobile force plates. Kinematic data were collected with five synchronized, panning, tilting, and zooming cameras. Inertial properties of the segments were calculated using an extended version of the Yeadon model. Knee joint forces and moments were calculated using inverse dynamics analysis. The obtained results indicate that knee joint loading in carving is not consistently greater than knee joint loading in skidding. In addition, knee joint loading at the outer leg is not always greater than at the inner leg. Differentiation is required between forces and moments, the direction of the forces and moments, and the phase of the turn that is considered. Even though the authors believe that the analyzed turns are representative, results have to be interpreted with caution due to the small sample size.

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Kevin R. Ford, Anh-Dung Nguyen, Eric J. Hegedus and Jeffrey B. Taylor

Virtual environments with real-time feedback can simulate extrinsic goals that mimic real life conditions. The purpose was to compare jump performance and biomechanics with a physical overhead goal (POG) and with a virtual overhead goal (VOG). Fourteen female subjects participated (age: 18.8 ± 1.1 years, height: 163.2 ± 8.1 cm, weight 63.0 ± 7.9 kg). Sagittal plane trunk, hip, and knee biomechanics were calculated during the landing and take-off phases of drop vertical jump with different goal conditions. Repeated-measures ANOVAs determined differences between goal conditions. Vertical jump height displacement was not different during VOG compared with POG. Greater hip extensor moment (P < .001*) and hip angular impulse (P < .004*) were found during VOG compared with POG. Subjects landed more erect with less magnitude of trunk flexion (P = .002*) during POG compared with VOG. A virtual target can optimize jump height and promote increased hip moments and trunk flexion. This may be a useful alternative to physical targets to improve performance during certain biomechanical testing, screening, and training conditions.