Effects of foot progression angle on knee mechanics during an anticipated cutting task: A statistical parametric mapping approach.

Cutting is considered a "high-risk" movement for anterior cruciate ligament (ACL) injuries. It has been established that sex differences exist during cutting, placing females at greater ACL injury risk. Foot progression angle (FPA) during landing has been shown to influence lower extremity mechanics, yet little is known how FPA influences mechanics during cutting. The purpose of this study was to compare two FPA conditions during cutting between males and females. Twenty-four males and females were tested using two FPA conditions: toe-in 15° (TI15) and toe-out 15° (TO15). Right knee joint kinematic and kinetic variables were measured using a motion capture system and force plate. Five successful trials were collected and compared between FPA conditions. One-dimensional statistical parametric mapping was used to assess changes in knee mechanics between males and females over the entire stance phase. The only sex × FPA effect found was knee flexion angle. Females cutting at TI15 had decreased knee flexion angle compared TO15 (p = 0.019). Significant sex main effects included knee abduction and rotation angles, and knee flexion and rotation moments. Significant FPA main effects included knee flexion, abduction and rotation angles. The results show cutting with a toe-in FPA of 15° is enough to induce changes in knee abduction angle while cutting with 15° toe-out FPA influenced knee flexion and rotation angles. These data suggest that different cutting FPAs may be influential on known ACL injury risk variables. However, more research is warranted on cutting FPA before FPA is targeted as part of ACL injury prevention protocols.

Increased Ankle Range of Motion Reduces Knee Loads During Landing in Healthy Adults.

Decreased dorsiflexion range of motion (DROM) can be modified using static stretching and joint mobilizations and may attenuate known knee anterior cruciate ligament injury risk factors. It is not known how these interventions compare to each other and how they improve knee landing mechanics. This study's purpose was to determine the immediate effects of static stretching and joint mobilization interventions on DROM measurement changes and right-leg drop jump knee landing mechanics. Eighteen females and 7 males, all recreationally active, completed 2 study sessions. Active and passive DROM, the weight-bearing lunge test, the anterior reach portion of the Star Excursion Balance Test, and a right-leg drop jump landing task were completed before and after the intervention. Change in DROM (ΔDROM) was calculated for DROM assessments between preintervention and postintervention. Pairwise dependent t tests determined no differences in ΔDROM between interventions, and statistical parametric mapping determined increased knee flexion (P = .004) and decreased anterior shear force (P = .015) during landing after both interventions. Increased DROM improves sagittal plane displacement and loading at the knee. Stretching may be a more feasible option in a healthy population for those wanting to maintain range of motion and decrease knee injury risk without physical therapist involvement.

Lower extremity muscle contributions to ACL loading during a stop-jump task.

Landing is considered a high-risk movement, especially landings from a stop-jump task, as they are often associated with lower extremity injuries, such as anterior cruciate ligament injuries (ACL). Females demonstrate lower extremity landing mechanics that often place them at a larger risk of injury compared to their male counterparts. While efforts have been made to understand lower extremity mechanics during stop-jump landings, little is known regarding the musculature function during these tasks and how they may influence ACL loading. Understanding lower extremity muscle contributions to ACL loading (FACL) may give insight to improving injury prevention protocols. Ten healthy, recreationally active females completed five trials of an unanticipated stop-jump task. Right leg kinematics, kinetics, and electromyography data were collected with three-dimensional motion capture, force plates, and electromyography sensors, respectively. Modified musculoskeletal models were scaled based on participant-specific anthropometrics, and muscle forces were obtained using static optimization. An induced acceleration analysis combined with a previously established mathematical ACL loading model was used to calculate lower extremity muscle contribution to FACL. The vastus lateralis, vastus intermedius, vastus medials, biceps femoris long head, semimembranosus, and soleus were found to be the primary contributors to FACL, with the vastus lateralis being the largest contributor. These data suggest that muscles traditionally known as ACL unloaders may in certain conditions load the ACL. These results also suggest that future injury prevention protocols should target muscles specifically to mitigate the influence the vastus lateralis has on ACL loading.

Type of unanticipated stimulus affects lower extremity kinematics and kinetics during sidestepping.

Including an unanticipated stimulus has significant impacts on lower extremity biomechanics during dynamic movements. It is unknown how a live, human defender affects lower extremity biomechanics. The purpose of this study was thus to determine the effects of two types of unanticipated stimuli (visual stimulus; defensive opponent) on lower extremity kinematics and kinetics in males and females during 45° sidestepping trials. Eight males and eight females completed two unanticipated stimuli sidestepping conditions. Numeric visual analog scales for reaction difficulty and movement realism were collected and analysed using a 2 × 2 mixed-model ANOVA. Three-dimensional hip, knee, and ankle kinematics and kinetics were measured during the stance phase of the sidestep and analysed using statistical parametric mapping. Participants reported greater difficulty and less realistic movements with the visual stimulus. Unanticipated stimulus main effects were observed for knee abduction angle, and hip extension and adduction, and knee extension and adduction moments. Sex main effects were observed for hip flexion, hip abduction, and ankle dorsiflexion angles, as well as hip abduction, ankle plantarflexion and ankle eversion moments and vertical ground reaction forces. Participants responded differently to two unanticipated stimuli. Careful consideration should be used when determining the type of unanticipated stimulus used.

Increased knee loading in stair ambulation in patients dissatisfied with their total knee replacement.

BACKGROUND: Total knee replacement patients have shown reductions in knee flexion range of motion, knee extensor moments, and gait speed during stair ascent and stair descent. However, it is unknown how patients dissatisfied with their total knee replacement differ from those who are satisfied during more difficult activities such as stair negotiation. Therefore, the purpose of this study was to compare knee biomechanics of patients who are dissatisfied with their joint replacement to those who are satisfied and healthy participants during stair negotiation. METHODS: Nine dissatisfied, fifteen satisfied patients and fifteen healthy participants participated, completing stair ascent and descent trials on an instrumented staircase. A 2 × 3 ANOVA was used to analyze biomechanical differences between groups and limbs during both activities. FINDINGS: The dissatisfied group showed reduced 2nd peak vertical GRF (P ≤ 0.0040) and loading-response knee extension moments (P ≤ 0.0041) in their operated limb compared to their non-operated limb and to satisfied and healthy groups during stair ascent. First peak vertical GRF (P < 0.0088) and both loading-response (P < 0.0117) and push-off abduction moments (P < 0.0028) showed reduced values in operated limbs compared to non-operated limbs for all groups. During stair descent, the dissatisfied group showed reduced loading-response and push-off knee extension moments (P ≤ 0.006) in their operated limb compared to their non-operated limb and the healthy group. The loading-response knee extension (P < 0.0379) and abduction moments (P ≤ 0.0048) were also reduced in the dissatisfied group compared to the satisfied group. INTERPRETATION: Patients who were dissatisfied showed asymmetrical loading of the knees in conjunction, which may have contributed to their dissatisfaction.

Hinged ankle braces do not alter knee mechanics during sidestep cutting.

Lateral ankle sprains are common injuries in quick, dynamic movements and are caused by rapid ankle inversion. Ankle braces are used to reduce ankle inversion, while allowing normal plantar and dorsiflexion ranges of motion. Knee injuries, such as anterior cruciate ligament injuries, are also common in dynamic movements. It is important to understand how ankle braces affect injury risk at other proximal joints. There is limited and conflicting results on how ankle braces affect knee mechanics during these types of movements. Additionally, it is unknown if sex differences exist when using an ankle brace. Therefore, the purpose of this study was to determine the effects of a hinged ankle brace and sex during a 45° cutting movement. Three-dimensional kinematics and ground reaction forces were collected using a motion capture system and force plate on ten men and eight women during cutting trials. 2 × 2 repeated measures ANOVAs were used to detect differences in ground reaction forces, as well as knee and ankle kinematics between brace conditions and sex (p < 0.05). The brace condition exhibited greater initial contact ankle dorsiflexion (p = 0.011), decreased peak ankle inversion (p < 0.01), and increased vertical loading rate (p = 0.040). Females performed the cutting movement with less initial contact (p = 0.019) and peak knee flexion (p = 0.023) compared to males. Ankle bracing had no impact on the observed sex differences. Females exhibited decreased knee flexion compared to males, which has been well documented in the literature. The use of an ankle braces reduced ankle injury risk variables while not adversely impacting knee mechanics during a 45° sidecutting movement.

Comparing Anterior Cruciate Ligament Injury Risk Variables Between Unanticipated Cutting and Decelerating Tasks.

To examine the relationship between anterior cruciate ligament injury risk factors in unanticipated cutting and decelerating. Three-dimensional kinematics and ground reaction forces were collected on 11 females (22 [2] y, 1.67 [0.08] m, and 68.5 [9.8] kg) during 2 unanticipated tasks. Paired samples t tests were performed to compare dependent variables between tasks. Spearman rank correlation coefficients were calculated to analyze the relationship between peak internal knee adduction moment and peak anterior tibial shear force (ASF) during 2 unanticipated tasks. Significantly greater knee abduction angles, peak knee adduction moments, and peak ASFs were observed during cutting (P ≤ .05). A strong positive correlation existed between decelerating ASF and cutting ASF (ρ = .67), while correlations between decelerating knee adduction moment and cutting knee adduction moment and decelerating ASF and cutting knee adduction moment were not significant. In situations where time management is a necessity and only one task can be evaluated, it may be more appropriate to utilize an unanticipated cutting task rather than an unanticipated deceleration task because of the increased knee adduction moment and ASF. These data can help future clinicians in better designing more effective anterior cruciate ligament injury risk screening methods.

Enhanced photoelectrochemical activity in all-oxide heterojunction devices based on correlated "metallic" oxides.

n-n Schottky, n-n ohmic, and p-n Schottky heterojunctions based on TiO2 /correlated "metallic" oxide couples exhibit strong solar-light absorption driven by the unique electronic structure of the "metallic" oxides. Photovoltaic and photocatalytic responses are driven by hot electron injection from the "metallic" oxide into the TiO2 , enabling new modalities of operation for energy systems.