Download or read book Muscle Force Contributions to Knee Joint Loading written by Nirav Maniar and published by . This book was released on 2017 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: Anterior cruciate ligament (ACL) injuries are one of the most common knee injuries suffered by athletic populations. ACL injuries are particularly burdensome due to potential surgical requirements, extensive rehabilitation time and associated financial costs for the individual and the community. Additionally, ACL injuries are associated with increased risk of early onset knee osteoarthritis. As such, ACL injury preventative and rehabilitative strategies are of paramount importance.ACL injuries typically occur during non-contact dynamic tasks, such as unanticipated sidestep cutting. At the time of injury, the knee joint experiences relatively large degrees of knee valgus and rotation (either internal or external) and high mechanical loads. These loading patterns, along with the anterior shear force, are known to increase loads on the ACL, especially in combination with each other. Muscles produce forces that can cause and oppose these knee joint loads, and therefore play a critical role in dictating the size and the nature of the loads experienced by the ACL. Prior research has investigated the role of muscle force in ACL load development, and has indicated that the hamstrings are most capable of reducing ACL loads. Subsequently, any pathology that may influence hamstring function may increase the risk of ACL injury. (...) The data from this program of research will inform ACL injury rehabilitation and injury prevention practices which should consider not only targeting the hamstrings but also other non-knee-spanning muscles for loading and unloading the knee during sidestep cutting. Additionally, this thesis provides data that may inform strategies aiming to modulate muscle forces to alter tibiofemoral compressive forces, which may be involved in ACL injury and concomitant meniscal and articular cartilage injury. Finally, this thesis provides further data informing how these muscles contribute to the performance of sidestep cut, in order to achieve optimal balance between performance and injury risk considerations. The findings from this thesis also dictates that future investigations that aim to examine the link between prior HSI and increased knee joint loading need to broaden the scope of such work to consider the influence of other lower-limb muscles as well as multi-planar movements.

Download or read book Examination of Muscular Contributions to Knee Joint Contact Loads During Healthy and Pathological Gait written by Christopher Richard Winby and published by . This book was released on 2008 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is thought that abnormalities in knee loads during walking are instrumental in the development and degradation of the joint tissues. These loads are extremely difficult to measure in-vivo and thus typically have been inferred from the external loads acting on the joint and muscle activity data (EMG) which are both relatively easy to measure. Large external adduction moments have been implicated in the development and progression of OA, knee joint pain, and worse outcomes after knee surgery such as high tibial osteotomy and it is thought this is due to these increasing the load sustained by the medial compartment of the knee. However, any estimates of joint loading should also include the contribution of the muscles as these have the capacity to stabilise the knee against large external loads, but may increase the joint contact loads as a result. Muscle activation patterns are known to be different in pathological gait, but it is not known whether these correspond to increased joint loads, as EMG does not necessarily represent muscle force. EMG-driven musculoskeletal modelling is a tool which facilitates the estimation of muscle force from EMG and this thesis is concerned with the application of such a model to gait to examine the contribution of the muscles to joint stabilisation and the subsequent joint contact forces. In order to apply the EMG-driven neuromuscular skeletal model to different subjects, an analytical scaling technique was developed to facilitate adjustment of selected muscle properties according to anthropometric dimensions. It adjusts these properties such that the force generating range of each muscle is preserved across subjects. It is suggested that this provides a good rationale for scaling muscle properties, and it is shown that the developed algorithm best achieves this compared to some other scaling techniques which have been presented previously.

Download or read book Musculoskeletal Disorders and the Workplace written by Institute of Medicine and published by National Academies Press. This book was released on 2001-05-24 with total page 510 pages. Available in PDF, EPUB and Kindle. Book excerpt: Every year workers' low-back, hand, and arm problems lead to time away from jobs and reduce the nation's economic productivity. The connection of these problems to workplace activities-from carrying boxes to lifting patients to pounding computer keyboards-is the subject of major disagreements among workers, employers, advocacy groups, and researchers. Musculoskeletal Disorders and the Workplace examines the scientific basis for connecting musculoskeletal disorders with the workplace, considering people, job tasks, and work environments. A multidisciplinary panel draws conclusions about the likelihood of causal links and the effectiveness of various intervention strategies. The panel also offers recommendations for what actions can be considered on the basis of current information and for closing information gaps. This book presents the latest information on the prevalence, incidence, and costs of musculoskeletal disorders and identifies factors that influence injury reporting. It reviews the broad scope of evidence: epidemiological studies of physical and psychosocial variables, basic biology, biomechanics, and physical and behavioral responses to stress. Given the magnitude of the problem-approximately 1 million people miss some work each year-and the current trends in workplace practices, this volume will be a must for advocates for workplace health, policy makers, employers, employees, medical professionals, engineers, lawyers, and labor officials.

Download or read book Joint Reaction Force and Contributions of Surrounding Muscles to Knee Joint Load During Stair Ascent in Total Knee Replacement Patients and Healthy Individuals written by Robert Jacob Rasnick and published by . This book was released on 2014 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt: [Abstract]

Download or read book Anatomical Guide for the Electromyographer written by Aldo Perotto and published by Charles C Thomas Publisher. This book was released on 2005 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Neuromuscular Strategies for Regulating Knee Joint Moments in Healthy and Injured Populations written by Teresa Flaxman and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Background: Joint stability has been experimentally and clinically linked to mechanisms of knee injury and joint degeneration. The only dynamic, and perhaps most important, regulators of knee joint stability are contributions from muscular contractions. In participants with unstable knees, such as anterior cruciate ligament (ACL) injured, a range of neuromuscular adaptations has been observed including quadriceps weakness and increased co-activation of adjacent musculature. This co-activation is seen as a compensation strategy to increase joint stability. In fact, despite increased co-activation, instability persists and it remains unknown whether observed adaptations are the result of injury induced quadriceps weakness or the mechanical instability itself. Furthermore, there exists conflicting evidence on how and which of the neuromuscular adaptations actually improve and/or reduce knee joint stability. Purpose: The overall aim of this thesis is therefore to elucidate the role of injury and muscle weakness on muscular contributions to knee joint stability by addressing two main objectives: (1) to further our understanding of individual muscle contribution to internal knee joint moments; and (2) to investigate neuromuscular adaptations, and their effects on knee joint moments, caused by either ACL injury and experimental voluntary quadriceps inhibition (induced by pain). Methods: The relationship between individual muscle activation and internal net joint moments was quantified using partial least squares regression models. To limit the biomechanical contributions to force production, surface electromyography (EMG) and kinetic data was elicited during a weight-bearing isometric force matching task. A cross-sectional study design determined differences in individual EMG-moment relationships between ACL deficient and healthy controls (CON) groups. A crossover placebo controlled study design determined these differences in healthy participants with and without induced quadriceps muscle pain. Injections of hypertonic saline (5.8%) to the vastus medialis induced muscle pain. Isotonic saline (0.9%) acted as control. Effect of muscle pain on muscle synergies recruited for the force matching task, lunging and squatting tasks was also evaluated. Synergies were extracted using a concatenated non-negative matrix factorization framework. Results/Discussion: In CON, significant relationships of the rectus femoris and tensor fascia latae to knee extension and hip flexion; hamstrings to hip extension and knee flexion; and gastrocnemius and hamstrings to knee rotation were identified. Vastii activation was independent of moment generation, suggesting mono-articular vastii activate to produce compressive forces, essentially bracing the knee, so that bi-articular muscles crossing the hip can generate moments for the purpose of sagittal plane movement. Hip ab/adductor muscles modulate frontal plane moments, while hamstrings and gastrocnemius support the knee against externally applied rotational moments. Compared to CON, ACL had 1) stronger relationships between rectus femoris and knee extension, semitendinosus and knee flexion, and gastrocnemius and knee flexion moments; and 2) weaker relationships between biceps femoris and knee flexion, gastrocnemius and external knee rotation, and gluteus medius and hip abduction moments. Since the knee injury mechanism, is associated with shallow knee flexion angles, valgus alignment and rotation, adaptations after ACL injury are suggested to improve sagittal plane stability, but reduce frontal and rotational plane stability. During muscle pain, EMG-moment relationships of 1) semitendinosus and knee flexor moments were stronger compared to no pain, while 2) rectus femoris and tensor fascia latae to knee extension moments and 3) semitendinosus and lateral gastrocnemius to knee internal rotation moments were reduced. Results support the theory that adaptations to quadriceps pain reduces knee extensor demand to protect the joint and prevent further pain; however, changes in non-painful muscles reduce rotational plane stability. Individual muscle synergies were identified for each moment type: flexion and extension moments were respectively accompanied by dominant hamstring and quadriceps muscle synergies while co-activation was observed in muscle synergies associated with abduction and rotational moments. Effect of muscle pain was not evident on muscle synergies recruited for the force matching task. This may be due to low loading demands and/or a subject-specific redistribution of muscle activation. Similarly, muscle pain did not affect synergy composition in lunging and squatting tasks. Rather, activation of the extensor dominant muscle synergy and knee joint dynamics were reduced, supporting the notion that adaptive response to pain is to reduce the load and risk of further pain and/or injury. Conclusion: This thesis evaluated the interrelationship between muscle activation and internal joint moments and the effect of ACL injury and muscle pain on this relationship. Findings indicate muscle activation is not always dependent on its anatomical orientation as previous works suggest, but rather on its role in maintaining knee joint stability especially in the frontal and transverse loading planes. In tasks that are dominated by sagittal plane loads, hamstring and quadriceps will differentially activate. However, when the knee is required to resist externally applied rotational and abduction loads, strategies of global co-activation were identified. Contributions from muscles crossing the knee for supporting against knee adduction loads were not apparent. Alternatively hip abductors were deemed more important regulators of knee abduction loads. Both muscle pain and ACL groups demonstrated changes in muscle activation that reduced rotational stability. Since frontal plane EMG-moment changes were not present during muscle pain, reduced relationships between hip muscles and abduction moments may be chronic adaptions by ACL that facilitate instability. Findings provide valuable insight into the roles muscles play in maintaining knee joint stability. Rehabilitative/ preventative exercise interventions should focus on neuromuscular training during tasks that elicit rotational and frontal loads (i.e. side cuts, pivoting maneuvers) as well as maintaining hamstring balance, hip abductor and plantarflexor muscle strength in populations with knee pathologies and quadriceps muscle weakness.

Download or read book The Effects of Knee Joint Loading on Dynamic Tasks in Individuals Several Years Post ACL Reconstruction written by Meredith Nannette Decker and published by . This book was released on 2020 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: Joint loading of the lower extremity is studied to identify risk factors for anterior cruciateligament (ACL) injuries and to determine limb asymmetries. Asymmetrical loading in the lower extremity during ACL reconstruction (ACLR) rehabilitation and at the time of return to sport or activity will cause compensations during functional movements, which can lead to unwanted joint re-injury or long-term joint damage. Re-injury and/or development and progression of knee osteoarthritis (OA) is prevalent after ACLR; therefore, joint loading measurements at extended time points from reconstruction and after return to play may help to identify how asymmetrical loading and compensatory movement strategies contribute to these occurrences. The joints of the lower extremity experience different stresses when ACLR individuals return to physical activity after clearance from rehabilitation because there are varying intensities and physical demands on individual athletes. Individuals also may actually avoid loading their ACLR knee because of persistent symptoms, poor perception, or limited knee extensor eccentric control . Therefore, our understanding of the impact of both excessive and limited knee joint loading on knee OA can be developed from an understanding of the normal and abnormal lower extremity movement patterns or strategies during various functional tasks in ACLR individuals. Study 1 (Chapter 2) takes a comprehensive approach to understand the difference in joint loading by way of energy absorption (EA) and energy absorption contribution (EAC) during three different functional tasks, single-leg squat (SLS), single-leg hop, and gait, in ACLR individuals 2-9 years removed from surgery and healthy, matched control participants. Advanced statistical analyses were used to identify interaction effects between each task within each group and between groups. There were differences between both groups in EA and EAC across all joints when comparing each physical performance task. Knee joint loading was greatest for both groups during the SLS task. ACLR participants utilized strategies with greater hip compensations during hop tasks and greater ankle contribution during gait tasks. These findings suggest the ability of ACLR participants to utilize altered loading strategies when performing different functional tasks and likely represent an avoidance of loading the knee of the surgical limb. The avoidance of knee joint loading in ACLR subjects are likely due to strength and range of motion asymmetries in the surgical limb compared to the non-surgical limb within ACLR subject as well as the matched limb within the healthy controls.Physical performance on different functional tasks is not only related to physical capacity but it is also related to a patient's self-efficacy related to the task, so it is important to measure a patient's perception of their capabilities as these cannot be objectively proven with lab tests.Self-reported function (SRF) has been utilized in conjunction with other biomechanical measures to explain kinetic and kinematic alterations; however, the comparison to EA and EAC has not been explored. Study 2 (Chapter 3) used performance on the previously mentioned physical performance tasks to identify an interaction effect with SRF, as measured by the Knee injury and Osteoarthritis Outcome Score (KOOS) and International Knee Documentation Committee (IKDC) forms. Overall, across functional tasks, ACLR subjects with lower SRF also used joint loading strategies that limited knee loading and emphasized hip and ankle compensations. These data support the notion that a lower perception of function will lead to changes in energy absorption. When compared to control subjects, ACLR subjects with SRF in either low or high sub-groups consistently demonstrated altered loading strategies with more ankle and/or hipcontribution in an effort to underload the knee. The findings of these investigations provide insightful information into energy absorption measures of joint loading within a variety of functional tasks in a previously unstudied time frame (2-9 years) following ACLR. Movement asymmetries and deficits in joint loading will impact knee joint health and the inclusion of measures of SRF are a necessary compliment to objective findings as understanding how ACLR individuals perceive their ability to load their surgical knee may help our understanding of asymmetrical loading patterns. Future work should identify EA and EAC across other performance tasks, in addition longitudinal investigations of joint loading and SRF in ACLR patients beyond the typical continuum of care from surgery through rehabilitation and return to activity should be pursued.

Download or read book Alterations in Joint Loading and Muscle Coordination Strategies with the Progression of Medial Compartment Knee Osteoarthritis written by Joseph A. Zeni (Jr) and published by ProQuest. This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Osteoarthritis (OA) is one of the leading causes of disability in the nation. With an increase in the middle age and elderly population, arthritis-related disability is expected to dramatically increase in the coming years. The mechanically initiated progression of the disease may stem from alterations in joint kinetics, kinematics and muscular control. The purpose of this work was to examine multiple facets of human gait that may contribute to altered joint loading and in turn, the progression of arthritis. This was addressed through four studies. In order to discern how persons with knee OA can decrease contribution of the knee to support during walking, the first study analyzed the contribution from ipsilateral joints to the total support moment. The results suggested that adaptive strategies are related to self-selected walking speed and involve a reduction of the knee contribution to support moment with a subsequent increase in ankle and hip contribution. The second study aimed to determine how differences in walking patterns affect a multitude of gait variables that have been previously associated with abnormal or detrimental joint loading. We attempted to differentiate between the adaptive gait strategies associated with alterations in walking speed and strategies that were an inherent part of the disease progression. The results from this study suggest that the selection of a slower self-selected walking speed reduces joint loading and appears to be a beneficial gait strategy, however certain potentially detrimental gait alterations exist regardless of freely chosen walking speed. The third study evaluated the effect of neuromuscular control on joint loading. Higher antagonistic muscle activity results in higher intersegmental forces. Analysis of muscular contribution to abnormal joint loading provides information beyond alterations in joint kinematics and kinetics. It was found that subjects with knee OA utilize higher co-contraction and potentially higher muscle forces during walking. The final study evaluated the potential end effect of alterations in muscular control on the dynamic joint stiffness in the knee during walking. Subjects with severe OA had higher levels of dynamic joint stiffness during walking than persons with less severe OA or persons without radiographic evidence of the disease. From these studies we have drawn two overall conclusions: (1) persons with knee OA exploit slower freely chosen walking speeds to reduce joint loading and (2) certain variables associated with detrimental effects on joint integrity cannot be reduced through the reduction of walking speed. This work should be used as the basis for future longitudinal studies which will help determine the effect of altered loading on joint progression and lead to rehabilitative strategies to reduce the progression of the disease.

Download or read book Contributions Made by the Medial Gastrocnemius Lateral Gastrocnemius and Plantaris Muscles to the Knee Joint Moment and to the Flow of Mechanical Energy Through the Lower Limb of Freely Moving Cats written by Thomas Alden Abelew and published by . This book was released on 1995 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Biomechanics and Motor Control of Human Movement written by David A. Winter and published by John Wiley & Sons. This book was released on 2009-10-12 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: The classic book on human movement in biomechanics, newly updated Widely used and referenced, David Winter's Biomechanics and Motor Control of Human Movement is a classic examination of techniques used to measure and analyze all body movements as mechanical systems, including such everyday movements as walking. It fills the gap in human movement science area where modern science and technology are integrated with anatomy, muscle physiology, and electromyography to assess and understand human movement. In light of the explosive growth of the field, this new edition updates and enhances the text with: Expanded coverage of 3D kinematics and kinetics New materials on biomechanical movement synergies and signal processing, including auto and cross correlation, frequency analysis, analog and digital filtering, and ensemble averaging techniques Presentation of a wide spectrum of measurement and analysis techniques Updates to all existing chapters Basic physical and physiological principles in capsule form for quick reference An essential resource for researchers and student in kinesiology, bioengineering (rehabilitation engineering), physical education, ergonomics, and physical and occupational therapy, this text will also provide valuable to professionals in orthopedics, muscle physiology, and rehabilitation medicine. In response to many requests, the extensive numerical tables contained in Appendix A: "Kinematic, Kinetic, and Energy Data" can also be found at the following Web site: www.wiley.com/go/biomechanics

Download or read book Handbook of Human Motion written by and published by Springer. This book was released on 2018-04-24 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Handbook of Human Motion is a large cross-disciplinary reference work which covers the many interlinked facets of the science and technology of human motion and its measurement. Individual chapters cover fundamental principles and technological developments, the state-of-the-art and consider applications across four broad and interconnected fields; medicine, sport, forensics and animation. The huge strides in technological advancement made over the past century make it possible to measure motion with unprecedented precision, but also lead to new challenges. This work introduces the many different approaches and systems used in motion capture, including IR and ultrasound, mechanical systems and video, plus some emerging techniques. The large variety of techniques used for the study of motion science in medicine can make analysis a complicated process, but extremely effective for the treatment of the patient when well utilised. The handbook descri bes how motion capture techniques are applied in medicine, and shows how the resulting analysis can help in diagnosis and treatment. A closely related field, sports science involves a combination of in-depth medical knowledge and detailed understanding of performance and training techniques, and motion capture can play an extremely important role in linking these disciplines. The handbook considers which technologies are most appropriate in specific circumstances, how they are applied and how this can help prevent injury and improve sporting performance. The application of motion capture in forensic science and security is reviewed, with chapters dedicated to specific areas including employment law, injury analysis, criminal activity and motion/facial recognition. And in the final area of application, the book describes how novel motion capture techniques have been designed specifically to aid the creation of increasingly realistic animation within films and v ideo games, with Lord of the Rings and Avatar just two examples. Chapters will provide an overview of the bespoke motion capture techniques developed for animation, how these have influenced advances in film and game design, and the links to behavioural studies, both in humans and in robotics. Comprising a cross-referenced compendium of different techniques and applications across a broad field, the Handbook of Human Motion provides the reader with a detailed reference and simultaneously a source of inspiration for future work. The book will be of use to students, researchers, engineers and others working in any field relevant to human motion capture.

Download or read book Sensitivity of Knee Joint Mechanics to Variations in Loading written by Jordan Lee and published by . This book was released on 1999 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Muscle Contributions to Knee Joint Stability written by Aaron Derouin and published by . This book was released on 2006 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Knee Stabilisation Strategies During an Isometric Weight Bearing Force Matching Task in Males and Females After ACL Injury written by Michael Del Bel and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The anterior cruciate ligament (ACL) plays an important role in knee joint stability, and unfortunately is one of the most commonly injured knee joint structures. The muscles surrounding the knee are also critical for stabilising the knee joint and their activations are altered following ACL injury. Despite the fact that ACL injuries are up to 8 times more likely to occur in females compared to males, there is limited research evaluating the effects of sex on how ACL-deficient individuals adjust neuromuscular control strategies during varying loading conditions. In order to have clinicians implement optimal rehabilitation strategies for ACL-deficient males and females, it is crucial to understand the adaptive functional strategies that are taking place once an ACL injury has occurred. The purpose of this thesis was therefore to provide objective and quantitative measurements describing the functional roles of muscles surrounding the knee. This was accomplished and outlined in this thesis through two chapters in manuscript format and summarised below. i) Sex and ACL-deficiency influence functional muscle roles during an isometric, weight-bearing, force-generation task First, the functional roles of muscles were quantified through the assessment of muscle activations during a series of multi-directional force-production tasks in ACL-deficient males and females while weight bearing. A highly controlled, isometric, force-matching task, whereby participants modulated ground reaction forces in various combinations of sagittal and frontal plane loads was used to quantify force-generation strategies (muscle activations and functional role) of the knee joint. Mean activation magnitudes and profile patterns from 10 muscles in the lower extremity (rectus femoris, vastus lateralis, vastus medialis, biceps femoris, semitendinosus, lateral gastrocnemius, medial gastrocnemius, tensor fascia latae, adductor muscle group, and gluteus medius) were recorded using wireless electromyography (EMG) sensors. Their activations were quantified with an orientation analysis to determine if differences in functional muscle roles existed between four groups; healthy female controls, healthy male controls, ACL-deficient females, and ACL-deficient males. Overall, different functional muscle roles were found between groups. Healthy male controls activated their muscles the most specifically; females with ACL-deficiency activated their muscles the least specifically, while healthy female controls and males with ACL-deficiency shared similar functional muscle roles. This suggests that there was a specificity hierarchy in the ability, or efficiency, to modulate the activation of muscles about the knee joint when exposed to various directional loading conditions. ii) Associations between subjective measures of knee dysfunction and measures of ground reaction forces in ACL-deficient males and females Correlational relationships were evaluated between perceived knee joint function and functional capacity of the knee joint. These relationships were calculated between patient reported outcome measures (PROM) from commonly used knee assessment scoring scales maximal generated forces in the sagittal and frontal planes. Both ACL-deficient groups had significantly lower perceived knee joint function compared to healthy controls. A trend towards significance was observed in the ability to generate maximum forces in the sagittal and frontal planes, with ACL-deficient females generating smaller maximal posterior GRFs compared to healthy females. Only two statistically significant correlations (both for ACL-deficient females) were found between maximal medial GRFs and patient reported outcome measures from the Lysholm and Tegner scoring scales. This indicates that there may be a discrepancy in the sensitivity of subjective outcome measures between sexes and their corresponding ability to generate maximum GRFs. In conclusion, sex differences exist in subjective outcome measures and the functional strategy of neuromuscular control of the knee joint both before and after ACL-injury. The results of this thesis indicate the need for sex-specific tailoring of rehabilitation programs, thus providing an opportunity to improve the success rate of rehabilitation following ACL-injury. Moreover, sensitivity of subjective outcome measures and their relation to simple, practical, functional tasks between sexes warrants further investigations.

Download or read book The Soft Hard Tissue Junction written by Neil D. Broom and published by Cambridge University Press. This book was released on 2018-11-29 with total page 810 pages. Available in PDF, EPUB and Kindle. Book excerpt: Richly illustrated throughout with actual tissue images, this innovative book shows that the soft-hard tissue junction is best understood in a biomechanical context. The authors describe their pioneering experimental methods, providing an essential structure-function framework for computational modelling, and thereby encouraging the development of more realistic, predictive models of this important tissue junction. Covering the three main musculoskeletal junctions of cartilage-bone, disc-vertebra, and ligament/tendon-bone, the relevant soft tissues are examined with respect to both their own inherent structure and their mode of integration with the hard tissue. The soft-hard tissue interface is explored with a focus on structural damage resulting from overloading, and its associated pathologies. Adopting a multiscale approach, ranging in structural resolution from the macro to fibril levels, this is a must-have guide to the field and an ideal resource for researchers seeking new and creative approaches for studying the joint and spine tissues.

Download or read book Computer Modeling of Muscle Coordination Strategies that Decrease Joint Loads written by Matthew Stephen DeMers and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Musculoskeletal models allow us to study muscle coordination and joint injuries in ways that in vivo experiments cannot. Models and simulations can compute internal joint contact forces, explore unsafe conditions, and simulate injuries without risk of harming experimental subjects. Models also enable systematic variation of muscle activity to evaluate its effect on joint loading and injury. The goals of this dissertation were to systematically quantify the effects of varied muscle activity in three applications: (1) to decrease knee forces during walking, (2) to estimate increased knee forces due to crouch gait in subjects with cerebral palsy, and (3) to prevent ankle sprains during landing. Muscles induce large forces in the tibiofemoral joint during walking and thereby influence the health or degradation of tissues like articular cartilage and menisci. It is possible to walk with a wide variety of muscle coordination patterns, but the effect of varied muscle coordination on tibiofemoral contact forces remains unclear. The first goal of this dissertation was to determine the effect of varied muscle coordination on tibiofemoral contact forces. We developed a musculoskeletal model of a subject walking with an instrumented knee implant. Using an optimization framework, we calculated the tibiofemoral forces resulting from muscle coordination that reproduced the subject's walking dynamics. We performed a large set of optimizations in which we systematically varied the coordination of muscles to determine the influence on tibiofemoral force. Peak tibiofemoral forces during late stance could be reduced by increasing the activation of the gluteus medius, uniarticular hip flexors, and soleus and by decreasing the activation of the gastrocnemius and rectus femoris. These results suggest that retraining of muscle coordination could substantially reduce tibiofemoral forces during late stance. Muscle coordination and the resulting tibiofemoral forces may vary dramatically due to changes in walking kinematics, especially for individuals with gait pathologies. Crouch gait, a common walking pattern in individuals with cerebral palsy, is characterized by excessive flexion of the hip and knee. Many subjects with crouch gait experience knee pain, perhaps because of elevated muscle forces and joint loading. The second goal of this dissertation was to examine how compressive tibiofemoral force change with the increasing knee flexion associated with crouch gait. Using our musculoskeletal model, muscle forces and tibiofemoral force were computed for three unimpaired children and nine children with cerebral palsy who walked with varying degrees of knee flexion. Compressive tibiofemoral force increased quadratically with average stance phase knee flexion (i.e., crouch severity) during the stance phase of walking, primarily due to concomitant increases in quadriceps forces. These results revealed that walking in crouch generates increased knee loading which may contribute to knee pain in individuals with crouch gait. Muscle coordination and pose are suspected causes and predictors of ankle inversion sprains. Interventions that retrain muscle coordination have helped rehabilitate injured ankles, but it is unclear which muscle coordination strategies, if any, can prevent ankle sprains. The third goal of this dissertation was to determine whether coordinated activity of the ankle muscles could prevent excessive ankle inversion during a simulated landing on a 30--degree incline. We used musculoskeletal simulations to evaluate two strategies for coordinating the ankle evertor and invertor muscles during simulated landing scenarios: planned co-activation and stretch reflex activation with physiologic latency (60-millisecond delay). Our simulations revealed that strong preparatory co-activation of the ankle evertors and invertors prior to ground contact prevented ankle inversion from exceeding injury thresholds by rapidly generating eversion moments after initial contact. Conversely, stretch reflexes were too slow to generate eversion moments before the simulations reached the threshold for inversion injury. These results suggest that training interventions to protect the ankle should focus on stiffening the ankle with muscle co-activation instead of increasing the speed or intensity of the evertor reflexes. This dissertation examines the effects of varied muscle coordination on two of the most common musculoskeletal injuries: chronic degradation of the knee and acute ankle inversion sprains. Our results revealed key connections between specific changes in muscle coordination and improved function of the knee and ankle, suggesting exciting future research areas for designing and testing interventions that protect knee and ankle function. Additionally, this dissertation provides a computational foundation for systematically exploring muscle coordination in musculoskeletal models, and provides them, free and open source, to the broader research community.

Download or read book Brace Yourself written by Scott Brandon and published by . This book was released on 2015 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compared with healthy controls, subjects with medial knee osteoarthritis walk using similar kinematics but greater activation of knee-spanning muscles, especially on the lateral side of the knee (furthest from centerline of the body). Although muscle forces generally compress the knee joint, it had been speculated that this specific activation pattern actually reduces compressive loads across the medial (closest to centerline) side of the knee where osteoarthritis is most common. It is not feasible to measure intra-articular contact forces in biological human knee joints. Therefore, a musculoskeletal simulation was developed to estimate the effect of elevated activation on knee contact forces. A generic musculoskeletal model was adapted to account for subject-specific frontal-plane alignment of the knee joint, and modified to isolate the medial and lateral components of the compressive knee contact load. The model's predictions were validated using in vivo data obtained from a subject with an instrumented knee prosthesis. Subsequently, the model was used to demonstrate that elevated muscle activation, as found in osteoarthritis subjects, does not protect against harmful medial loads, but actually contribute to an increase in peak load shortly after heel-strike. Since osteoarthritis subjects did not appear to adopt a protective gait pattern, the second half of the dissertation was devoted to the evaluation of a clinical device that is known to reduce medial loads during gait: the knee unloader brace. To accomplish medial unloading, braces apply a frontal plane abduction moment to the knee which, if large enough, would pry open the medial contact surfaces. A novel method was developed to non-invasively compute the abduction moment applied by the brace to each subject's leg using a mechanical stiffness calibration. The computed brace moment was incorporated into the musculoskeletal model in order to quantify relative contributions of muscle forces, inverse dynamic joint loads, and the applied brace load in reducing medial contact forces for treatment of medial knee osteoarthritis. The model revealed that kinematic, muscular, and inverse dynamic changes were dominated by the large applied brace moment. The medial unloading effect of knee braces could be enhanced by reducing external and muscle forces through gait modification.