Effects of Small and Normalized Q-Factor Changes and Knee Alignment on Knee Biomechanics During Stationary Cycling

Increasing inter-pedal distance (Q-Factor; QF) in cycling increases peak internal knee abduction moments (KAbM). The effect of smaller, normalized changes in QF has not been investigated, and the effect of static knee alignment at varying QFs is unknown. Purpose: The primary purpose of this study was to see if significant changes in KAbM were detectable with normalized increases in QF that are smaller than what has previously been investigated. The secondary purpose of this study was to investigate whether static knee alignment accounts for any changes in knee biomechanics while cycling at different QFs. Methods: Fifteen healthy participants were included in this study (7 Males, 8 Females, age: 22.7±2.5 years, BMI: 23.95±3.21 kg/m2 ; Mean±STD). Motion capture and instrumented pedals were used to collect kinematic (240 Hz) and pedal reaction force (PRF, 1200 Hz) data, respectively, while cycling at five different QFs. The participant’s mechanical axis angle (MAA) was determined using motion capture. Each participant’s QFs were normalized by starting at 160 mm and increasing by 2% of the participant’s trochanteric leg length (L) where the five QF conditions were (in mm): Q1 (160), Q2 (160 + 0.02*L), Q3 (160 + 0.04*L), Q4 (160 + 0.06*L), and Q5 (160 + 0.08*L). A mixed model analysis of variance was performed to detect differences between QF conditions (α = 0.05). Correlation was calculated between MAA and select variables. Results: KAbM was increased by at least 30% in Q5 from Q1, Q2, Q3, and Q4. Medial PRF was increased by at least 20% in Q5 from Q1, Q2, and Q3. There were no significant changes seen in peak vertical PRF, sagittal-plane moments and angles, or peak abduction angle that were concurrent with significant changes in KAbM. MAA had varying degrees of correlation with the variables of interest. Conclusions: These results suggest that KAbM is more sensitive to changes in QF at greater QF increases. The effect of MAA on frontal-plane knee biomechanics requires further investigation

3D Knee Kinematics and Kinetics With Visual Disruption in Subjects With ACL Reconstruction

BACKGROUND AND PURPOSE: The anterior cruciate ligament (ACL) is a commonly ruptured ligament among male and female athletes. Women are at a higher risk of ACL injuries compared to men. The leading cause of female ACL injuries has been identified as non-contact mechanisms. Several risk factors for injury among females that have been theorized include: quadriceps/hamstring activation pattern and force production, greater dynamic knee valgus, hormonal influenced laxity and anatomical gender variation. The purpose of this research was to analyze three dimensional (3D) kinetic and kinematic dynamic landing patterns at the knee between ACL reconstructed and healthy females and any interaction effects of visual disruption. METHODS: Seventeen healthy female subjects (25.3± 6 y) and 17 female subjects with an ACL reconstruction (26.5± 6.3 y) were studied. A 3D electromagnetic system measured knee position during a cutting maneuver from an athletic stance position. Anatomic boney landmarks on the occiput, sacrum, femur and tibia were digitized for capture. Subjects began on a force plate and were instructed to catch a ball and cut immediately left or right as indicated by a specific tone, which was randomized (40 trials). Vision was randomly disrupted via shutter glasses for either one second at the beginning of the cutting maneuver or was left intact for the duration of the movement. A two-way repeated measures ANOVA analyzed the differences between healthy and ACL reconstructed subjects and intact vision versus disrupted vision. RESULTS: The results indicate significant differences exist between subjects with ACL reconstruction and healthy subjects for flexion, adduction, and external rotation knee angles and extension, abduction, and internal rotation moments. Significant interactions of group and vision conditions also exist for flexion, adduction, and external rotation knee angles. Vision alone displayed no significant differences for all subjects. CONCLUSION: Years later, subjects with ACL reconstructions continue to display different knee kinematics and kinetics that could increase their risk for re-injury or injury of other leg. Furthermore, visual disturbances have significant effects on ACL reconstructed knee angles and moments when landing compared to healthy subjects. These results support continued movement related rehabilitation with visual disturbances for ACL reconstructed patients

Biomechanical models of the lower limb and pelvis, for female human gait in regular and overload conditions related to pregnancy.

Doutoramento em Motricidade Humana na especialidade de BiomecânicaA gravidez é uma fase especial da vida , considerando as adaptações morfológicas, fisiológicas, biomecânicas e hormonais vivenciadas pelas mulheres durante cerca de 40 semanas e no período pós-parto, podendo modificar o padrão de marcha e contribuir para uma sobrecarga no sistema músculo-esquelético, causando dor nos membros inferiores, bacia e zona lombar. Os objetivos do presente trabalho foram: 1) analisar a marcha de mulheres grávidas no segundo trimestre; 2) comparar as adaptações biomecânicas da marcha, entre as mulheres grávidas no segundo trimestre, mulheres não grávidas e mulheres com condições de sobrecarga artificiais; 3) analisar modelos biomecânicos com quatro set ups diferentes de análise; e, 4) analisar um modelo de contacto que determina a força vertical de reação do apoio. Os resultados demonstraram que as mulheres grávidas têm uma padrão de marcha similar ao normal. Observou-se que o ganho do peso no tronco aumenta o tempo das fases de apoio e de duplo apoio, quer nas mulheres grávidas quer nas mulheres com carga adicional. A resposta ao momento externo flexor da anca está relacionada com maior atividade dos extensores para suportar a carga anterior do tronco na direção da translação do centro de massa. Nas mulheres grávidas, o modelo universal-revolução-esférica afetou mais as variáveis cinemáticas quando comparado com o modelo de juntas com seis graus de liberdade. O modelo de contacto entre o pé e o solo, sobrestimou as forças verticais de reação. O aumento da massa do pé, devido ao inchaço consequente da gravidez, reduz a rigidez durante a fase de apoio. Os resultados do presente trabalho serão úteis para promover a investigação biomecânica do padrão de marcha durante a gravidez.FCT - Fundação para Ciência e a Tecnologi

The effects of foot structure, footwear and technique on knee joint loads in over ground running.

Research is yet to consider the influence of forefoot structure on forefoot pronation, its interaction with footwear and the ramifications for knee joint loading when performing endurance running (ER). This thesis investigated the relationships between forefoot structure, forefoot pronation, footwear choice, running technique and knee joint loading. Chapter four examined the measurement error of ER kinematics and kinetics within a test session, between sessions on the same day and between two days. Absolute measurement error for all kinematic and kinetic comparisons were ≤7.62° and ≤0.59 Nm·Kg-1 respectively. Results were used to assess habituation to novel footwear conditions and calculate sample size in subsequent studies. Using data from chapter four, chapter five investigated time to habituate in novel running conditions (barefoot, minimal and maximally-cushioned footwear) in a sample of recreational runners. Twentyone minutes was sufficient to establish consistent hip, knee and ankle sagittal plane kinematics, where variability was less than or equal to previously established within-session data. Post habituation, chapter six investigated associations between foot structure, forefoot pronation and peak-knee adduction moment, and the effect of running condition on forefoot pronation. Hallux angle and phalange width accounted for 35% of variance in forefoot pronation (P = 0.029). Results also showed forefoot pronation was significantly associated (P < 0.05) with peak-knee adduction moment (r = -0.57, r = -0.77, r = -0.61, for barefoot, minimal and structured-cushioned shoes, respectively). A medial translation in the centre of pressure was not associated with increased forefoot pronation. Footwear also influenced forefoot pronation. Minimal footwear had greater forefoot pronation compared to barefoot (P = 0.042) and the structured-cushioned condition (P = 0.001). Chapter seven examined the effects of footwear on lower-limb kinematics and kinetics. Compared to barefoot and minimal shoes, a more extended knee and dorsiflexed ankle at initial contact, increased peak-knee flexion moment, and reduced the peak-dorsiflexion moment were observed in maximally-cushioned shoes. An extended lower limb follows previous work that suggests insulation of mechanoreceptors would encourage a running technique that projects the foot more anteriorly to reduce ground contacts for a given distance. These kinematic changes also suggested overstride would increase as participants change from barefoot to maximally-cushioned footwear. Subsequently, chapter eight investigated the effects of footwear on overstride and its association with peak-knee adduction moment. Changing from maximally cushioned, to minimal shoes or barefoot, reduced overstride relative to the hip, whereas overstride relative to the knee decreased from maximally cushioned to barefoot only. Results also showed moderate to strong positive correlations between overstride and peak-knee adduction moment in all running conditions. Findings suggest footwear influences overstride, overstride was associated with peak-knee adduction moment, and reducing overstride might reduce peak-knee adduction moment, a variable associated with injury. Following observed relationships in chapter eight, chapter nine attempted to reduce peak-knee adduction moment. Twelve recreational endurance runners performed either a 30-minute run, or 30 minutes of gait retraining. The intervention had a primary focus on reducing overstride following the reported relationship between overstride and peak-knee adduction moment. Controlling for baseline measures, there was no significant difference between overstride, trunk lean and subsequently peakknee adduction moment. The lack of difference was attributed to the short duration and the acute nature of the coaching session. Similar investigations over a longer period of time are warranted. Collectively, phalange width and hallux angle contributed to forefoot pronation, and forefoot pronation was associated with peak-knee adduction moment when running, a measure associated with injury. This suggests those with compromised forefoot structure, might be at risk of injury, particularly when attempting to run barefoot or in minimal shoes that lack support. As participants changed from barefoot to minimal to maximally-cushioned footwear overstride increased, with medium to strong positive correlations for overstride and peak-knee adduction moment. This suggests runners with a large overstride are likely to be exposed to increased peak-knee adduction moment and potentially injury, and reduced overstride might present a means to reduce injury

Quantifying Joint Coordination Variability in Anterior Cruciate Ligament-Reconstructed Individuals During Walking

The knee is the second most common joint to sustain injury. An estimated 200,000 anterior cruciate ligament (ACL) ruptures occur each year in the United States alone, and about 100,000 ACL reconstruction (ACLR) surgeries are performed annually. There is a significant risk of developing osteoarthritis of the knee after incurring an ACL injury, and the incidence of ipsilateral or contralateral injury is six times greater in individuals who have a surgically repaired ACL. Past studies have analyzed kinetic and kinematic characteristics of individual lower extremity joints to reveal differences between subjects with and without ACLR. Despite reports of altered kinematic performance in individuals with ACLR compared to healthy controls, most of the analyses did not evaluate coordinative function, and thus neglected to consider how the lower limb acts as a linked chain. Therefore, the present study used a method based on dynamical systems theory to quantify coordination and account for the interaction between joints in the lower extremity. The purpose of the study was to quantify and compare joint coordination variability and joint coordination patterns between individuals with ACLR and matched controls. Institutional Review Board (IRB) approval was obtained prior to data collection, and all subjects signed an informed consent form. Twenty subjects (nine females, eleven males; body mass index (BMI) 25±3.5 kg/m2) who had undergone unilateral ACLR (thirteen right, seven left) and been cleared to return to full activity were compared to twenty control subjects matched by gender and BMI (nine females, eleven males; BMI 22.4±2.4 km/m2). Kinematic and kinetic data during walking were collected in the UTHSC Motion Analysis Laboratory. A vector coding technique was used to calculate coupling angles for six joint couplings involving the hip, knee, and ankle across four periods within the stance phase. Joint coordination variability was defined as the standard deviation of the coupling angle between trials within a subject, and joint coordination patterns were based on coupling angle magnitude. Individuals with ACLR exhibited increased joint coordination variability and altered joint coordination patterns compared to the matched controls during the stance phase of walking. These results suggested that coordinative function may not be fully restored in individuals with ACLR following rehabilitation. Increased coordination variability from a normal, or optimal amount as well as altered coordination patterns may result from a deficit in sensorimotor control, and represent risk of re-injury. Further investigation that is prospective, focuses primarily on hip-knee coupled motion in frontal and transverse planes, and includes assessment of EMG in addition to kinematics may contribute relevant information for improving ACL injury prevention and rehabilitation

Kinetic and 3D Kinematic analysis of netball movements: with and without prophylactic knee bracing

Patellofemoral pain is one of the most common musculoskeletal pain conditions, with a multifactorial aetiology. It is reported that young females are at high risk of developing patellofemoral pain. During dynamic, fast-paced games athletes are exposed to high ground reaction forces, contributing to lower body injury occurrence during landing and high patellofemoral loads. Knee braces, such as knee sleeves, are commonly used for patellofemoral pain; however the underlying mechanisms on the patellofemoral joint remain unclear. An increase in understanding of joint mechanics during sporting and functional tasks could help our understanding of injury mechanisms and preventative interventions. The aim is to identify any changes in the kinetics and kinematics of the tibiofemoral joint and the patellofemoral loading experienced in healthy subjects during a range of functional movements with and without a prophylactic knee sleeve

Biomechanical risk factors and reduced bone health in lower limb amputees

Bone constantly adapts to its surroundings through the formation and resorption of material, controlled by bone modelling and remodelling. Strains produced by mechanical loading are one factor that drive these processes and thus determine bone health. Lower limb amputees (LLA) adopt an asymmetrical movement pattern to compensate for the loss of a limb, resulting in a change in mechanical loading and subsequently a degradation in bone health. The aetiology of the majority of amputations is vascular diseases, which affect bone health. Therefore, it is not clear whether the asymmetrical loading, or comorbidities cause the degradation in bone health in LLA. Finite element models (FEM) are used to generate strain plots and predict the bone's response to mechanical loading. To understand the relationship between the degradation in bone health and asymmetrical loads in LLAs the asymmetrical loads can be applied to a healthy bone using FEMs, or simulated within a healthy population using restrictive devices. Therefore, the overall aim was to investigate the relationship between asymmetrical loading, as observed in LLA’s, and bone health, through the use of semi-subject specific FEMs and restrictive lower limb devices. Study one established a novel image processing method to convert peripheral quantative computed tomography (pQCT) scan images into binary and segment the tibia. The outer perimeter of the tibia was identified and sectioned to produce landmarks. The outer geometry landmarks were used to morph a base FEM, constructed from open source scan images to create semi-subject tibia FEM. Study two applied subject-specific joint reaction and muscle forces to the semi-subject tibia FEM. The strain plots output from Study two were validated against longitudinal geometrical changes from Study three. Study three, used 3D motion capture, pQCT and dual energy x-ray absorptiometry (DXA) to investigate gait and tibial geometry within a lower limb amputee and able-bodied population across twelve months. The coefficient of variation (CV) for able bodied subjects was less than 10% for ground reaction force (GRF) in level walking and less than 4% for bone total area. Study four, used a rigid foot orthosis and a trans-femoral prosthesis, to restrict able-bodied gait. Results showed participants walked significantly slower (p<0.01) in the restricted conditions, with a longer non-restricted step length (p<0.001). The loading rate and maximum GRF were higher in the non-restricted limb (p<0.05). Larger knee adductor moments were shown in the un-restricted leg in the trans-tibial condition (p<0.05). This thesis presents a novel method of constructing semi-subject specific FEMs from pQCT scans. This can be used to further investigate the link between asymmetrical loading and bone health in LLA's and other populations with asymmetrical gait. The use of restrictive devices allow investigation into LLA's specifically, without the interference of prosthetic variability, or comorbidities

Giving Way Event During a Combined Stepping and Crossover Cutting Task in an individual with Anterior Cruciate Ligament Deficiency

Study Design: Case study. Objective: To compare knee kinematics and moments of nongiving way trials to a giving way trial during a combined stepping and crossover cutting activity. Background: The knee kinematics and moments associated with giving way episodes sugge motor control strategies that lead to instability and recovery of stability during movement. Methods and Measures: A 27-year-old woman with anterior cruciate ligament deficiency reported giving way while performing a combined stepping and crossover cutting activity. P motion analysis system recorded motion of the pelvis, femur, tibia, and foot using 3 infrarec emitting diodes placed on each segment at 60 Hz. Force plate recordings at 300 Hz were combined with limb inertial properties and position data to estimate net knee joint moments. The stance time, foot progression angle, and cutting angle were also included to evaluate performance between trials. Results: Knee internal rotation during the giving way trial increased 3.2\u27 at 54% of stance relative to the nongiving way trials. Knee flexion during the giving way trial increased to 33.1 at 66% of stance, and the knee moment switched from a nominal flexor moment to 2 knee extensor moment at 64% of stance. The knee abductor moment and external rotation moment during the giving way trial deviated in early stance. Conclusions: The observed response to the giving way event suggests that increasing knee flexion may enhance knee stability for this subject. The transverse and frontal plane moments appear important in contributing to the giving way event. Further research that assists clinicians in understanding how interventions can impact control of movements in these planes is necessary

Effects of Workrate and Seat Position on Frontal Plane Knee Biomechanics in Recumbent Cycling

In cycling study, most of the research focused on the sagittal plane lower extremity biomechanics and upright cycling. However, few of them paid attention to the frontal plane and recumbent cycling. Internal knee abduction moment (KAbM), on the frontal plane, has been shown to be an effective predictor of knee osteoarthritis (OA), and recumbent bicycle has become the newest popular tool of rehabilitation. The purpose of this study was to examine the effects of different workrates and seat positions on knee frontal plane biomechanics during stationary recumbent cycling. Thirteen participants took part in the study. 6 total conditions of one-minute cycling at the cadence of 80 RPM were assigned to each participant: pedaling at “flexed”, “optimal” and “extended” seat positions (largest knee extension angle of 10-20 degrees, 20-30 degrees, and 30-40 degrees, respectively) with 60 and 100 W of workrate. A 3D motion analysis system and a pair of custom-made instrumented pedals were used to collect kinematic and kinetic data