Peak Knee Extension Moment Research Articles

Effects of Workloads and Cadences on Frontal Plane Knee Biomechanics in Cycling.

Although effects of workload and cadence on sagittal plane knee biomechanics in cycling have been widely studied, few studies have examined their impact on the frontal plane. The purpose of this study was to investigate the effects of different workloads and cadences on knee sagittal and frontal plane biomechanics. Eighteen healthy participants (age, 55.7 ± 11.0 yr) volunteered for this study. A motion analysis system and a custom instrumented pedal were used to collect five cycles of three-dimensional kinematics (240 Hz) and pedal reaction force (PRF, 1200 Hz) during 2 min of cycling in each of eight testing conditions, including five workload conditions of 0.5, 1, 1.5, 2, and 2.5 kg at 60 rpm, and three cadence conditions of 70, 80, and 90 rpm with 1-kg workload. Two one-way repeated measures analyses of variance were used to examine the influence of cadence and workload on selected variables (P < 0.05). Increased workloads with constant rpm caused an increased peak knee abduction moment from 5.82 to 14.36 N · m and peak knee extension moment from 11.61 to 37.16 N · m. Increased workloads also significantly increased peak medial and vertical PRF. Increased cadences at the constant workload had no effects on peak knee abduction moment but caused increased peak anterior and vertical PRF and peak knee flexion moment. The findings of this study indicate that increasing workload at constant cadence significantly increased peak knee abduction moment. Further study may be needed to demonstrate the efficacy of appropriate levels of workload and cadence in knee osteoarthritis and other populations with knee problems.

Rearfoot Landing Technique Increases Knee Loading during Sidestep Cutting Maneuvers by Basketball Players

1.1. Objectiveː Many non-contact anterior cruciate ligament (ACL) injuries in female basketball athletes occur during the deceleration phase of sidestep cutting maneuvers. However, few studies have attempted to quantify the kinetic and kinematical parameters related to landing technique during sidestep cutting maneuvers by basketball players. The objective of this study was to evaluate the effects of forefoot and rearfoot landing techniques on trunk and lower extremity kinetic and kinematic parameters during sidestep cutting maneuvers in this population. 1.2. Methodsː Fourteen healthy female collegiate basketball athletes performed forefoot or rearfoot landing technique randomly during sidestep cutting maneuvers. The trunk and lower extremity kinetic and kinematic variables of the non-dominant leg were analyzed during landing. The variables between forefoot and rearfoot landings during these maneuvers were compared. 1.3. Resultsː Rearfoot landings showed increased peak knee flexion angle and extension moment during the deceleration phase of sidestep cutting maneuvers, as compared to forefoot landing (p<0.05), whereas forefoot landing showed increased peak hip flexion angle (p<0.05). 1.4. Conclusionː The rearfoot landing technique increases knee extension moment, which may potentially place increased strain on the ACL. Therefore, forefoot landing techniques should be adopted during the train and completion of basketball for ACL injury prevention.

Biomechanics of Load Carriage--Historical Perspectives and Recent Insights.

Loads carried by the warfighter have increased substantially throughout recorded history, with the typical U.S. ground soldier carrying external loads averaging 45 kg during operations in Afghanistan. Incidence of disability in the U.S. Army has also increased sixfold since the 1980s, predominantly driven by increases in musculoskeletal injuries, with load carriage implicated as a possible mechanism. This article will provide a brief overview of the biomechanics of load carriage and will provide some recent insights into how the stress of the loads carried by military personnel can affect the musculoskeletal system. Studies into the biomechanics of load carriage have documented motion-related differences such as increased step rate, decreased stride length, and more trunk lean with increases in pack-borne loads. However, there is a paucity of literature on the relationship between load carriage and biomechanical mechanisms of overuse injury. Findings of recent studies will be presented, which add mechanistic information to increased stresses on the lower extremity. This was particularly true at the knee, where in one study, peak knee extension moment increased 115% when carrying a 55 kg load (0.87 ± 0.16 Nm·kg⁻¹) vs. no external load (0.40 ± 0.13 Nm·kg⁻¹). Efforts to model injury mechanisms require continued biomechanical measurements in humans while carrying occupationally relevant loads to be validated. Specifically, imaging technologies (e.g., bone geometry scans) should be incorporated to produce higher fidelity model of the stresses and strains experienced by the load carrier. In addition to laboratory-based biomechanics, data are needed to further explore the mechanistic relationship between load magnitude and injury; to this end, wearable sensors should continue to be exploited to accurately quantify biomechanical stresses related to load carriage in the field.

Young Athletes With Quadriceps Femoris Strength Asymmetry at Return to Sport After Anterior Cruciate Ligament Reconstruction Demonstrate Asymmetric Single-Leg Drop-Landing Mechanics

Background: Young athletes who have had anterior cruciate ligament (ACL) reconstruction demonstrate suboptimal rates of return to sport, high rates of second ACL injuries, and persistent movement asymmetries. Therefore, the influence of musculoskeletal impairments on movement mechanics in this population needs to be further evaluated. Hypothesis: The primary hypothesis was that among young athletes who have had ACL reconstruction, those with greater quadriceps strength asymmetry would demonstrate altered single-leg drop-landing mechanics at return to sport compared with individuals with more symmetric quadriceps strength and also compared with healthy controls (ie, those with no ACL reconstruction). A second hypothesis was that quadriceps strength symmetry would predict single-leg drop-landing symmetry in individuals who have undergone ACL reconstruction. Study Design: Controlled laboratory study. Methods: The study entailed a total of 103 participants (age, 17.4 years) at the time of return to sport after ACL reconstruction and 47 control participants (age, 17.0 years). The quadriceps index (QI) was calculated for isometric quadriceps strength, which was then used to divide the ACL reconstruction participants into high-quadriceps (QI ≥90%; n = 52) and low-quadriceps (QI <85%; n = 41) subgroups. Biomechanical data were collected by use of 3-dimensional motion analysis during a single-leg drop-landing task. The LSI was calculated for kinematic and kinetic sagittal-plane variables of interest during landing. Group differences were compared by use of 1-way analysis of variance and linear regression analyses (α < .05). Results: Both the low- and high-quadriceps groups demonstrated greater limb asymmetry during landing compared with the control group in knee flexion excursion (mean LSI ± SD: low quadriceps, 85.8% ± 15.5% [P < .001]; high quadriceps, 94.2% ± 15.6% [P = .019]; control, 102.7% ± 14.1%), peak trunk flexion angle (low quadriceps, 129.2% ± 36.6% [P < .001]; high quadriceps, 110.5% ± 22.6% [P = .03]; control, 95.5% ± 26.2%), and peak knee extension moment (low quadriceps, 79.5% ± 25.2% [P < .001]; high quadriceps, 89.9% ± 19.8% [P = .005]; control, 102.2% ± 10.9%). Compared with the high-quadriceps group, the low-quadriceps group also demonstrated greater asymmetry during landing in knee flexion excursion (P = .026), peak trunk flexion angle (P = .006), and peak knee extension moment (P = .034). In the ACL reconstruction group, quadriceps strength symmetry predicted symmetry in knee flexion excursion, peak trunk flexion, and peak knee extension moment (all P < .001) and predicted symmetry in peak trunk flexion angle (P < .001) after controlling for graft type, knee-related pain, function with activities of daily living, and sport function. Conclusion: At the time of return to sport, athletes who had undergone ACL reconstruction, including those in both the high- and low-quadriceps groups, demonstrated asymmetry during a single-leg drop-landing task compared with controls. Compensations included increased trunk flexion, decreased knee flexion excursion, and decreased knee extension moments on the involved limb. In addition, individuals in the low-quadriceps group demonstrated greater movement asymmetry compared with individuals in the high-quadriceps group. Clinical Relevance: Restoration of symmetric quadriceps strength after ACL reconstruction is associated with more symmetric mechanics during a single-leg drop-landing movement. However, this appears to be multifactorial, as the high-quadriceps group also demonstrated landing asymmetries. Restoration of symmetric quadriceps strength may improve postoperative athletic participation; however, future study is warranted.

Biomechanical gait characteristics of naturally occurring unsuccessful foot clearance during swing in individuals with chronic stroke

BackgroundAltered gait mechanics are common following stroke and may increase the risk of falls. Paretic gait impairments have been previously compared to the non-paretic limb or control participants. Unfortunately, the biomechanical parameters underlying instances of naturally occurring unsuccessful foot clearance (trips) have yet to be examined in individuals with chronic stroke. MethodsGait data from 26 participants with chronic stroke were obtained on a dual-belt instrumented treadmill. Instances of successful and unsuccessful foot swing were identified. Temporal, kinematic, and kinetic measures of the paretic limb occurring during late stance, toe-off, and swing were compared between trip and non-trip steps using paired samples t-tests. An α=0.004 was used to adjust for multiple comparisons. FindingsIn the paretic limb, the ankle angle at toe off (P=0.003; d=0.64), knee flexion velocity at toe off (P<0.001; d=0.73), and peak knee extension moment during terminal stance (P<0.001; d=0.74) were significantly different between trips and non-trip steps. During trip steps, ankle plantarflexion at toe-off was 1.0° greater, knee flexion velocity was reduced by 17.6°/sec, and peak knee extension moment was increased by 0.011Nm/kg·m compared to non-trip steps. InterpretationIt appears to take only minor changes in the movement of the paretic limb to result in a trip in individuals with chronic stroke. Although small, the multi-joint biomechanical changes occurring in the paretic limb during unsuccessful foot clearance result in a functionally longer limb. Thus, interventions targeting multiple joints in the paretic limb may be needed to reduce the risk of trips following stroke.

Gender differences of sagittal knee and ankle biomechanics during stair-to-ground descent transition

BackgroundFalls on stairs often result in severe injury and occur twice as frequently in women. However, gender differences in kinetics and kinematics during stair descent are unknown. Thus, this study aimed to determine whether gender differences of knee and ankle biomechanics exist in the sagittal plane during the stair-to-ground descending transition. It was hypothesized that 1) women would reveal higher ground-toe-trochanter angle and lower ground-toe length during stair-to-ground descent transition than men; and 2) women would reveal lower peak knee extension moment during stair-to-ground descent transition than men. MethodsFifteen men and fifteen women were recruited and performed a stair descent activity. Kinetic and kinematic data were obtained using a force plate and motion capture system. FindingsThe women performed the stair descent with a lower peak knee extension moment and a peak knee power at the early weight acceptance phase. The women also revealed a higher ground-toe-trochanter angle and a lower ground-toe length, which indicated a more forward position of the lower extremity relative to the toe contact point at both the initial contact and at the time of peak kinematic and kinetic events. InterpretationThis study found that knee and ankle kinematics and kinetics differed significantly between the genders due to differences in ground-toe-trochanter angle. Women have a different stair descending strategy that reduces the demand of the lower extremity muscle function, but this strategy seems to increase the risk of falls.

Influence of Total Knee Arthroplasty on Gait Mechanics of the Replaced and Non-Replaced Limb During Stair Negotiation

This study compared biomechanics during stair ascent in replaced and non-replaced limbs of total knee arthroplasty (TKA) patients with control limbs of healthy participants. Thirteen TKA patients and fifteen controls performed stair ascent. Replaced and non-replaced knees of TKA patients were less flexed at contact compared to controls. The loading response peak knee extension moment was greater in control and non-replaced knees compared with replaced. The push-off peak knee abduction moment was elevated in replaced limbs compared to controls. Loading and push-off peak hip abduction moments were greater in replaced limbs compared to controls. The push-off peak hip abduction moment was greater in non-replaced limbs compared to controls. Future rehabilitation protocols should consider the replaced knee and also the non-replaced knee and surrounding joints.

The Evaluation of Vertical Pole Configuration and Location on Assisting the Sit-to-Stand Movement in Older Adults with Mobility Limitations

Grab-bars and transfer poles are common sit-to-stand aids for mobility limited older adults. This study investigated differences in kinetics and kinematics to characterize the lower-limb strength and dynamic balance requirements across different pole configurations and positions in nine mobility limited older adults. Poles were varied by location (near and far) and configuration (single vertical pole, double vertical poles, vertical pole with a horizontal bar). Results indicated that the far pole condition resulted in increased trunk (p < 0.001) and hip flexion (p < 0.01 and < 0.0001 for contralateral and ipsilateral sides, respectively), and a reduced peak vertical force applied to the pole (p < 0.001). Peak extension moments at the hip and knee were unchanged, and, therefore, pole position had no effect on task demands. Placing the pole unilaterally introduced a small kinetic asymmetry, which significantly increased peak knee extension moments on the ipsilateral side (p < 0.05). Finally, dynamic balance was relatively unchanged across pole conditions. These findings offer novel insight into pole use and the effect of varying pole location and configuration in a sample of older adults with mobility impairment, and provide the basis for future work.

Differences in Gait Biomechanics in Obese and Healthy Young Adults

Obesity is considered a risk factor for knee osteoarthritis (KOA). Patients with KOA display alterations in gait biomechanics, which contribute to development and progression of the disease. However, this research has focused on older adults, and it is unclear if young obese individuals display similar aberrant biomechanics. Also, it is unclear if obesity contributes to KOA or results from the associated decline in physical activity. PURPOSE: To compare knee kinematics and kinetics during walking between healthy-weight and obese young adults. METHODS: 15 healthy weight (males = 7, age = 20.42±1.4 years, body mass index = 21.5±1.1) and 15 obese (males = 7, age = 21.2±1.2 years, body mass index = 33.5±3.7) healthy young adults were recruited and categorized using body mass index (BMI). Obesity was defined as having a BMI≥30. Three-dimensional kinematics and kinetics were collected while participants walked overground at standardized (1 m/s) and self-selected speeds. Independent samples t-tests were used to compare peak vertical ground reaction force (vGRF), vGRF loading rate, peak knee extension moment, peak knee adduction moment, and knee flexion excursion between groups. Forces and loading rates were normalized to body weight (BW) and joint moments were normalized to the product of body weight and height. RESULTS: Gait biomechanics did not differ between groups during walking at a self-selected speed with the exception that obese subjects displayed lesser knee flexion excursion (6.54° vs. 10.22°, p<0.001). However, when walking at a standardized speed, obese subjects displayed a greater average (0.32 vs. 0.30 N/s/BW, p=0.002) and instantaneous vertical LR (46.17 vs. 35.02 N/s/BW, p<0.001) vGRF loading rates and lesser knee flexion excursion (5.52° vs. 7.67°, p=0.04). CONCLUSIONS: These results suggest that obesity may contribute to the development of KOA via greater vertical loading rates rather than resulting from it. Future prospective studies are needed to identify the relationship of higher loading rates on knee joint health.

Effects of Workload on Frontal Plane Knee Biomecahnics during Cycling

Cycling is a recommended exercise for individuals with knee osteoarthritis (OA) because of its low impact loading to lower extremity joints. Effects of workload on sagittal plane knee biomechanics in cycling have been widely studied. However, few studies have examined impacts of workload on frontal plane biomechanics. PURPOSE: To investigate the effects of different workloads on frontal plane knee loading related biomechanical characteristics. METHODS: Eighteen healthy participants (mean±SD; age: 55.7±11.0 years, height: 1.80±0.10 m, weight: 78.8±6.3 kg) cycled on a stationary ergometer for two minutes at five different workloads (0.5, 1, 1.5, 2, and 2.5 kg) at 60 revolutions per minute (RPM). Three-dimensional kinematics (240 Hz) and pedal reaction force (PRF, 1200 Hz) using an instrumented pedal were collected for five pedal cycles. Selected knee kinetic variables were compared using a one-way repeated measures ANOVA (alpha=0.05). RESULTS: Peak medial PRF significantly increased between 0.5 (8.0 N) and 1 kg (20.4 N), 1.5 kg (27.6 N), 2 kg (34.8 N), and 2.5 kg (36.0 N), and between 1 and 1.5 kg and 2 kg (all comparisons, p < 0.05). Peak knee abduction moment significantly increased when workloads increased from 0.5 kg (-5.82 Nm) to 1 kg (-9.5 Nm), 1.5 kg (-10.18 Nm), 2 kg (-11.6 Nm), and 2.5 kg (-14.36 Nm) (all comparisons p < 0.05). Furthermore, peak knee extension moment increased significantly (p≤0.003) with increased workload between all pairs of workloads of 0.5 kg (11.6 Nm), 1 kg (20.2 Nm), 1.5 kg (26.0 Nm), 2 kg (34.2 Nm) and 2.5 kg (37.2 Nm) except for the difference between 2 and 2.5 kg. CONCLUSION: The results indicate that increased workload at a constant pedal cadence caused increased peak knee abduction moments as well as peak knee extension moments. During exercise or rehabilitation, a low cycling workload may be appropriate for individuals with medial knee OA in order to minimize loading to the knee joint. Future studies may be needed to establish appropriate levels of workload for knee OA and other knee pathological populations.

The Kinematics and Kinetics Analysis of the Lower Extremity in the Landing Phase of a Stop-jump Task.

Large number of studies showed that landing with great impact forces may be a risk factor for knee injuries. The purpose of this study was to illustrate the different landing loads to lower extremity of both genders and examine the relationships among selected lower extremity kinematics and kinetics during the landing of a stop-jump task. A total of 35 male and 35 female healthy subjects were recruited in this study. Each subject executed five experiment actions. Lower extremity kinematics and kinetics were synchronously acquired. The comparison of lower extremity kinematics for different genders showed significant difference. The knee and hip maximum flexion angle, peak ground reaction force and peak knee extension moment have significantly decreased during the landing of the stop-jump task among the female subjects. The hip flexion angle at the initial foot contact phase showed significant correlation with peak ground reaction force during landing of the stop-jump task (r=-0.927, p<0.001). The knee flexion angle at the initial foot contact phase had significant correlation with peak ground reaction force and vertical ground reaction forces during landing of the stop-jump task (r=-0.908, p<0.001; r=0.812, P=0.002). A large hip and knee flexion angles at the initial foot contact with the ground did not necessarily reduce the impact force during landing, but active hip and knee flexion motions did. The hip and knee flexion motion of landing was an important technical factor that affects anterior cruciate ligament (ACL) loading during the landing of the stop-jump task.

Male and female runners demonstrate different sagittal plane mechanics as a function of static hamstring flexibility.

ABSTRACTBackground: Injuries to runners are common. However, there are many potential contributing factors to injury. While lack of flexibility alone is commonly related to injury, there are clear differences in hamstring flexibility between males and females. Objective: To compare the effect of static hamstring length on sagittal plane mechanics between male and female runners. Method: Forty subjects (30.0±6.4 years) participated and were placed in one of 4 groups: flexible males (n=10), inflexible males (n=10), flexible females (n=10), and inflexible females (n=10). All subjects were free of injury at the time of data collection. Three-dimensional kinematics and kinetics were collected while subjects ran over ground across 2 force platforms. Sagittal plane joint angles and moments were calculated at the knee and hip and compared with a 2-way (sex X flexibility) ANOVA (α=0.05). Results: Males exhibited greater peak knee extension moment than females (M=2.80±0.47, F=2.48±0.52 Nm/kg*m, p=0.05) and inflexible runners exhibited greater peak knee extension moment than flexible runners (In=2.83±0.56, Fl=2.44±0.51 Nm/kg*m, p=0.01). For hip flexion at initial contact, a significant interaction existed (p<0.05). Flexible females (36.7±7.4º) exhibited more hip flexion than inflexible females (27.9±4.6º, p<0.01) and flexible males (30.1±9.5º, p<0.05). No differences existed for knee angle at initial contact, peak knee angle, peak hip angle, or peak hip moment. Conclusion: Hamstring flexibility results in different mechanical profiles in males and females. Flexibility in the hamstrings may result in decreased moments via active or passive tension. These differences may have implications for performance and injury in flexible female runners.

The Effects of 2 Landing Techniques on Knee Kinematics, Kinetics, and Performance During Stop-Jump and Side-Cutting Tasks

Background: Anterior cruciate ligament injuries (ACL) commonly occur during jump landing and cutting tasks. Attempts to land softly and land with greater knee flexion are associated with decreased ACL loading. However, their effects on performance are unclear. Hypothesis: Attempts to land softly will decrease peak posterior ground-reaction force (PPGRF) and knee extension moment at PPGRF compared with a natural landing during stop-jump and side-cutting tasks. Attempts to land with greater knee flexion at initial ground contact will increase knee flexion at PPGRF compared with a natural landing during both tasks. In addition, both landing techniques will increase stance time and lower extremity mechanical work as well as decrease jump height and movement speed compared with a natural landing during both tasks. Study Design: Controlled laboratory study. Methods: A total of 18 male and 18 female recreational athletes participated in the study. Three-dimensional kinematic and kinetic data were collected during stop-jump and side-cutting tasks under 3 conditions: natural landing, soft landing, and landing with greater knee flexion at initial ground contact. Results: Attempts to land softly decreased PPGRF and knee extension moment at PPGRF compared with a natural landing during stop-jump tasks. Attempts to land softly decreased PPGRF compared with a natural landing during side-cutting tasks. Attempts to land with greater knee flexion at initial ground contact increased knee flexion angle at PPGRF compared with a natural landing during both stop-jump and side-cutting tasks. Attempts to land softly and land with greater knee flexion at initial ground contact increased stance time and lower extremity mechanical work, as well as decreased jump height and movement speed during both stop-jump and side-cutting tasks. Conclusion: Although landing softly and landing with greater knee flexion at initial ground contact may reduce ACL loading during stop-jump and side-cutting tasks, the performance of these tasks decreased, as indicated by increased stance time and mechanical work as well as decreased jump height and movement speed. Clinical Relevance: Training effects tested in laboratory environments with the focus on reducing ACL loading may be reduced in actual competition environments when the focus is on athlete performance. The effects of training programs for ACL injury prevention on lower extremity biomechanics in athletic tasks may need to be evaluated in laboratories as well as in actual competitions.

Comparisons of increases in knee and ankle joint moments following an increase in running speed from 8 to 12 to 16 km·h− 1

BackgroundKnowledge regarding knee and ankle joint load across a range of running speeds is important, if running related injuries are to be prevented. The purpose of the present study was to test the hypothesis that peak plantar flexion moment increases relatively more than peak knee extension moment when running speed is increased. MethodsKinematic and ground reaction force data were collected from 33 recreational runners during steady-state running at three different speeds: 7.96km·h−1 (SD 0.18), 11.92km·h−1 (SD 0.25) and 15.91km·h−1 (SD 0.36). Peak plantar flexion moment and peak knee extension moment were calculated using a standard three-dimensional inverse dynamics approach. FindingsThere was a significant interaction between the joint location and the running speed (P=0.03): When running speed increased from 7.96 to 15.91km·h−1, mean peak plantar flexion moment increased by 0.74N·m·kg−1 (95% CI: 0.64; 0.85) which was more than the 0.52N·m·kg−1 (95% CI: 0.42; 0.63) increase in mean peak knee extension moment. InterpretationA greater increase in biomechanical load occurs for the plantar flexors of the ankle joint than for the extensors of the knee joint when running speed increases. This may indicate that at an excessive running speed, the structures at the posterior part of the lower leg and underneath the foot are relatively more vulnerable to injury compared with the structures at the anterior part of the knee. As a considerable load reduction is achieved, a decrease in running speed may benefit rearfoot striking recreational runners experiencing pain in the posterior lower leg or underneath the foot.

The effect of ankle–foot orthosis plantarflexion stiffness on ankle and knee joint kinematics and kinetics during first and second rockers of gait in individuals with stroke

BackgroundStiffness of an ankle–foot orthosis plays an important role in improving gait in patients with a history of stroke. To address this, the aim of this case series study was to determine the effect of increasing plantarflexion stiffness of an ankle–foot orthosis on the sagittal ankle and knee joint angle and moment during the first and second rockers of gait. MethodsGait data were collected in 5 subjects with stroke at a self-selected walking speed under two plantarflexion stiffness conditions (0.4Nm/° and 1.3Nm/°) using a stiffness-adjustable experimental ankle–foot orthosis on a Bertec split-belt fully instrumented treadmill in a 3-dimensional motion analysis laboratory. FindingsBy increasing the plantarflexion stiffness of the ankle–foot orthosis, peak plantarflexion angle of the ankle was reduced and peak dorsiflexion moment was generally increased in the first rocker as hypothesized. Two subjects demonstrated increases in both peak knee flexion angle and peak knee extension moment in the second rocker as hypothesized. The two subjects exhibited minimum contractility during active plantarflexion, while the other three subjects could actively plantarflex their ankle joint. InterpretationIt was suggested that those with the decreased ability to actively plantarflex their ankle could not overcome excessive plantarflexion stiffness at initial contact of gait, and as a result exhibited compensation strategies at the knee joint. Providing excessively stiff ankle–foot orthoses might put added stress on the extensor muscles of the knee joint, potentially creating fatigue and future pathologies in some patients with stroke.

Frontal plane knee mechanics and medial cartilage MR relaxation times in individuals with ACL reconstruction: A pilot study

BackgroundThe objective of this pilot study was to evaluate cartilage T1ρ and T2 relaxation times and knee mechanics during walking and drop-landing for individuals with anterior cruciate ligament reconstruction (ACL-R). MethodsNine patients (6 men and 3 women, age 35.8±5.4years, BMI 23.5±2.5kg/m2) participated 1.5±0.8years after single-bundle two-tunnel ACL reconstruction. Peak knee adduction moment (KAM), flexion moment (KFM), extension moment (KEM), and peak varus were calculated from kinematic and kinetic data obtained during walking and drop-landing tasks. T1ρ and T2 times were calculated for medial femur (MF), and medial tibia (MT) cartilage and compared between subjects with low KAM and high KAM. Biomechanical variables were compared between limbs. ResultsThe high KAM group had higher T1ρ for MT (p=0.01), central MT (p=0.05), posterior MF (p=0.04), posterior MT (p=0.01); and higher T2 for MT (p=0.02), MF (p=0.05), posterior MF (p=0.002) and posterior MT (p=0.01). During walking, ACL-R knees had greater flexion at initial contact (p=0.04), and lower KEM (p=0.02). During drop-landing, the ACL-R knees had lower KAM (p=0.03) and KFM (p=0.002). ConclusionPatients with ACL-R who have higher KAM during walking had elevated MR relaxation times in the medial knee compartments. These data suggest that those individuals who have undergone ACL-R and have higher frontal plane loading, may be at a greater risk of knee osteoarthritis.

Comparison of support leg kinetics between side-step and cross-step cutting techniques

The purpose of this study was to investigate differences in the support leg joint moment and moment power between side-step (SS) and cross-step (CS) cutting techniques with a prescribed 90° cutting angle. Ground reaction forces (1,000 Hz) and three-dimensional kinematics (250 Hz) of SS and CS cutting techniques were collected from 20 male college athletes. Normalised peak knee extension moment was larger in the SS technique than in the CS technique (0.40 ± 0.10 in SS; 0.26 ± 0.08 in CS). In the SS technique, the knee extensors ( − 0.10 ± 0.06 in SS; − 0.02 ± 0.04 in CS) and ankle plantarflexors ( − 0.12 ± 0.05 in SS; − 0.07 ± 0.03 in CS) did significantly more negative work (normalised). The direction change angle (40.5 ± 8.7° in SS; 33.0 ± 6.8° in CS) and the decrease in horizontal velocity of the centre of mass ( − 0.63 ± 0.23 m/s in SS; − 0.31 ± 0.23 m/s in CS) were significantly larger in the SS technique. These results suggest that the SS technique is an effective means of changing running direction at the expense of velocity of the centre of mass and that the CS technique is better for minimising the reduction in horizontal velocity of the centre of mass.

EFFECT OF AN INTERNALLY VERSUS EXTERNALLY FOCUSED ACL INJURY PREVENTION PROGRAM ON INJURY RISK

BackgroundAnterior cruciate ligament (ACL) injury prevention programs have shown mixed results, which may be in part due to suboptimal training components.ObjectiveDetermine effects of a prevention program with external and internal...

Effects of adding a virtual reality environment to different modes of treadmill walking

Differences in gait between overground and treadmill walking are suggested to result from imposed treadmill speed and lack of visual flow. To counteract this effect, feedback-controlled treadmills that allow the subject to control the belt speed along with an immersive virtual reality (VR) have recently been developed. We studied the effect of adding a VR during both fixed speed (FS) and self-paced (SP) treadmill walking. Nineteen subjects walked on a dual-belt instrumented treadmill with a simple endless road projected on a 180° circular screen. A main effect of VR was found for hip flexion offset, peak hip extension, peak knee extension moment, knee flexion moment gain and ankle power during push off. A consistent interaction effect between VR and treadmill mode was found for 12 out of 30 parameters, although the differences were small and did not exceed 50% of the within subject stride variance. At FS, the VR seemed to slightly improve the walking pattern towards overground walking, with for example a 6.5mm increase in stride length. At SP, gait became slightly more cautious by adding a VR, with a 9.1mm decrease in stride length. Irrespective of treadmill mode, subjects rated walking with the VR as more similar to overground walking. In the context of clinical gait analysis, the effects of VR are too small to be relevant and are outweighed by the gains of adding a VR, such as a more stimulating experience and possibility of augmenting it by real-time feedback.

Does the rectus femoris nerve block improve knee recurvatum in adult stroke patients? A kinematic and electromyographic study

Knee recurvatum (KR) during gait is common in hemiplegic patients. Quadriceps spasticity has been postulated as a cause of KR in this population. The aim of this study was to assess the role of rectus femoris spasticity in KR by using selective motor nerve blocks of the rectus femoris nerve in hemiparetic stroke patients. The data from six adult, post-stroke hemiplegic patients who underwent a rectus femoris nerve block for a stiff-knee gait were retrospectively analyzed. An extensive clinical and functional evaluation was performed and gait was assessed by motion analysis (kinematic, kinetic and electromyographic parameters) before and during the block realized using 2% lidocaine injected under a neurostimulation and ultrasonographic targeting procedure. The main outcome measures were the peak knee extension in stance and peak knee extensor moment obtained during gait analysis. No serious adverse effect of the nerve block was observed. The block allowed a reduction of rectus femoris overactivity in all patients. Peak knee extension and extensor moment in stance did not improve in any patient, but peak knee flexion during the swing phase was significantly higher after block (mean: 31.2° post, 26.4 pre, p<0.05). Our results provide arguments against the hypothesis that the spasticity of the rectus femoris contributes to KR.