Application of Computational Lower Extremity Model to Investigate Different Muscle Activities and Joint Force Patterns in Knee Osteoarthritis Patients during Walking

Many experimental and computational studies have reported that osteoarthritis in the knee joint affects knee biomechanics, including joint kinematics, joint contact forces, and muscle activities, due to functional restriction and disability. In this study, differences in muscle activities and joint force patterns between knee osteoarthritis (OA) patients and normal subjects during walking were investigated using the inverse dynamic analysis with a lower extremity musculoskeletal model. Extensor/flexor muscle activations and torque ratios and the joint contact forces were compared between the OA and normal groups. The OA patients had higher extensor muscle forces and lateral component of the knee joint force than normal subjects as well as force and torque ratios of extensor and flexor muscles, while the other parameters had little differences. The results explained that OA patients increased the level of antagonistic cocontraction and the adduction moment on the knee joint. The presented findings and technologies provide insight into biomechanical changes in OA patients and can also be used to evaluate the postoperative functional outcomes of the OA treatments

Musculoskeletal Loads during Stationary Cycling and the Effects of Pedal Modifications for Knee Osteoarthritis

Knee OA is a deteriorating joint disease affecting 27 million people in the US and current exercise prescriptions may be improved with new knowledge of their effects on muscle forces and joint contact loads. Cycling rather than other exercise modalities is generally considered an alternative for people with knee OA. If these research objectives were achieved, clinicians would have additional tools related to joint contact loads for treating people with OA with an cycling exercise while controlling progression of OA. The long-term goal of this research is to provide a scientific basis for planning, evaluation and improvement of subject-specific rehabilitation for subjects with knee osteoarthritis (OA). The principles governing relationships between muscle forces, joint contact loads and movements in people with knee OA, have not been discovered. Determining how to adjust movements to optimize joint contact loads is difficult because experiments do not account for these loads. In combination with experimental approaches, muscle-actuated inverse dynamic simulations provide a scientific framework to estimate important variables and identify cause-and- effect relationships. These activities challenge existing paradigms for exercise prescriptions by including movements specifically designed for decreasing knee joint contact loads. The research objective is to investigate muscle forces and joint contact loads that are experienced by the knee during cycling. The overall hypothesis is a combination of biomechanical cycling modifications that contribute to altered muscle forces and a reduction in knee joint contact loads in subjects with and without knee OA during cycling; this may be mitigated with a novel pedal design. The overall purpose of this research was to discover relationships between muscle forces, joint contact loads, cycling and OA-friendly cycling modifications for improving exercise prescriptions. The following objectives were addressed: 1) determine the effects of lateral pedal wedges and toe-in on joint biomechanics during cycling and 2) examine the potential of optimization to design subject-specific cycling modifications for decreasing knee joint contact loads

Strategies Utilized during a Novel Rotary Task in Total Knee Replacement Subjects

The ability to perform activities of daily living involving flexion/extension of the knee along with rotation are crucial for total knee replacement (TKR) patients to regain their independence post-surgery. The proposed research identified compensatory strategies used by TKR subjects during a novel rotary task. The task consisted of two activities, a high to low (H2L) and a low to high (L2H) button task where subjects utilized a crossover technique in order to press buttons located at shoulder and knee height by flexing and extending the knee. Ground reaction forces and kinematics were recorded for eleven TKR subjects and twelve healthy controls. Data were modeled in a musculo-skeletal modeling system to determine knee torque, center of mass displacement, and muscular activity. Each leg was categorized as affected (TKR knee), unaffected (non-TKR limb), or a healthy control. No statistical differences were found in the force transfer for the different groups, although differences in the variation of the loading within subjects were noted. Differences were found between healthy and unaffected knee angles and a strong trend between healthy and affected subject's knee angles in both tasks. L2H had the most variation where a significant difference was present predominantly between unaffected and healthy in the knee flexion, knee torque, and hip extensor muscles. Consistencies during both tasks in knee torque and muscle activation while knee angles varied suggests the kinematics during this type of motion is driven by the cross over. These outcomes suggest that individuals with a TKR may utilize strategies, such as keeping an extended knee and altered muscle activation, to achieve rotary tasks during knee flexion and extension, yet these strategies were not reported consistently from task to task. Early identification of these strategies could improve TKR success and the return to activities of daily living that involve flexion and rotation

Impact of Footwear on Mechanisms of Knee Osteoarthritis Progression

Knee osteoarthritis (OA) is a debilitating disease affecting the entire knee joint by inducing pathological changes to the cartilage and menisci. Currently, the etiology of OA is not completely understood. However, altered gait mechanics, specifically increased joint loading, of OA patients have a clear association with both symptomatic and structural OA progression. Non-surgical intervention tools, such as variable stiffness shoes (VSS), have been developed as a way to decrease loading within the knee joint. However, with external moments being surrogate measures for knee loading, it is unclear if changes in knee moments with the footwear are sufficient to result in a clinical benefit. Therefore, this project’s purpose was to investigate whether a VSS intervention can alter knee joint loading and menisci function in a knee OA population. We used gait analysis, musculoskeletal modeling, and finite element (FE) analysis to determine the effect of VSS on gait mechanics, knee joint contact force, and menisci stress and strain, compared to a control shoe. We found knee moments did not decrease with the VSS intervention. Furthermore, participants who did experience a decrease in knee adduction moment did not always experience a decrease in medial compartment contact force. However, results from our FE modeling of the tibiofemoral joint indicate significant changes in knee joint contact force can influence stress placed on the menisci. Results from this study suggest knee contact forces and tissue stress, not only external moments, should be considered when investigating if VSS can positively impact an OA population

Predictions of Knee Joint Contact Forces Using Only Kinematic Inputs with a Recurrent Neural Network

BACKGROUND: Knee joint contact (bone on bone) forces are commonly estimated using surrogate measures such as external knee adduction moments (with limited success) or musculoskeletal modeling (more successful). Despite its capabilities, modeling is not optimal for clinicians or persons with limited experience and knowledge. Therefore, the purpose of this study was to design a novel prediction method for knee joint contact forces that is equal or more accurate than modeling, yet simplistic in terms of required inputs. METHODS: This study included all six subjects’ (71.3±6.5kg, 1.7±0.1m) data from the opensource “Grand Challenge” datasets (simtk.org) and two subjects from the CAMS datasets, consisting of motion capture and in-vivo instrumented knee prosthesis data (e.g. true knee joint contact forces). Inverse kinematics were used to derive three-dimensional hip, two-dimensional knee (sagittal & frontal), and one-dimensional ankle (sagittal) kinematics during the stance phase of normal walking for all subjects. Medial and lateral knee joint contact forces (normalized to body weight) and inverse kinematics were imported into MATLAB and normalized to 101 data points. A long-short term memory network (LSTM) was created to predict knee forces using combinations of the kinematics inputs. The Grand Challenge data were used for training, while the CAMS data were used for testing. Waveform accuracy was explained by the proportion of variance and root mean square error between network predictions and in-vivo knee joint contact forces data. RESULTS: The top five networks demonstrated excellent fit with the training data, achieving RMSE \u3c 0.26BW for medial and lateral forces, R2 \u3e 0.69 for medial forces, but only R2 \u3e 0.15 for lateral forces. The overall best-selected network contained frontal hip and knee, and sagittal hip and ankle input variables and presented the finest visual waveform agreement with the in vivo data (R2=0.77, RMSE=0.27). CONCLUSIONS: The LSTM network designed in this study revealed knee joint forces could accurately be predicted by using only kinematic input variables. The network’s results outperformed most reports of root mean squared errors and correlation coefficients attained by musculoskeletal modeling and surrogate measures of KAMs

Musculoskeletal Models in a Clinical Perspective

This book includes a selection of papers showing the potential of the dynamic modelling approach to treat problems related to the musculoskeletal system. The state-of-the-art is presented in a review article and in a perspective paper, and several examples of application in different clinical problems are provided

DYNAMIC SIMULATION AND ANALYSIS OF GAIT MODIFICATION FOR TREATING KNEE OSTEOARTHRITIS

Roughly 47.5 million people in the US have a disability, with 8.6 million reporting arthritis as their main cause of disability, making arthritis the leading cause of physical disability. With decreased mortality rates and a large, aging baby boomer generation, there will be more adults living with chronic musculoskeletal conditions causing disabilities that limit walking. Since walking ability is directly related to an individual’s independence at home and in the community, losing this ability is a major setback for patients with arthritis. Knee osteoarthritis (OA) is the most prevalent form of arthritis affecting approximately 27 million adults and accounts for over 55% of all arthritis-related hospital admissions. OA is a highly painful disease with treatments limited to pain management. However, gait modification has recently shown promise as an early intervention treatment strategy to slow disease progression. Thus, the objective of this dissertation is to investigate subject-specific gait modifications to minimize joint loads for treating patients with knee OA. The first study in this dissertation relies heavily on the development of subject-specific musculoskeletal models to analyze muscle forces and joint contact loads during toe-in gait modification for subjects with knee OA. This study will generate muscle-actuated, dynamic simulations to estimate muscle forces and internal joint contact loads during gait. The results of this study will aid in the advancement of gait modification as a treatment strategy for knee OA. The last two studies will employ machine learning and optimization techniques— specifically, forward sequential feature selection and surrogate-based optimization— to evaluate toe-in gait modification and improve its efficacy for use as a treatment strategy for knee OA. The goal will be to develop testable subject-specific gait modification patterns that reduce joint loads. The use of both dynamic simulations and data mining techniques provides a unique approach to investigating the relationship between joint biomechanics and muscle function and joint contact loads with respect to gait modification. This approach has the potential to gain much needed insight into the underlying mechanism of gait modification and help advance research to create subject-specific gait modification patterns for treating knee OA in the future

Quantifying the effects of pediatric obesity on musculoskeletal function and biomechanical loading during walking

2015 Spring.Includes bibliographical references.With the high prevalence of pediatric obesity worldwide, there is a critical need for structured physical activity interventions during childhood. However, obese children exhibit altered walking mechanics that are associated with decreased gait stability, reduced walking performance and an increased prevalence of musculoskeletal pain and pathology. Left unaddressed, the increased pain and orthopedic conditions associated with pediatric obesity may lead to reduced physical activity and a cycle of perpetual weight gain for the child and future adult. To enhance the efficacy of health and weight loss interventions, clinicians could benefit from an improved understanding of how pediatric obesity affects the neuromuscular and musculoskeletal systems during walking, the most common form of daily activity. The mechanisms for the altered gait and associated risks to the developing musculoskeletal system in obese children are not well understood, particularly as they relate to excess adiposity and exercise related fatigue. This void in the literature may be attributed in part to the lack of experimental and computational tools necessary to accurately quantify muscle function and joint loads during walking in obese and healthy-weight adults and children. Therefore, to improve our understanding of the musculoskeletal mechanisms for the altered gait mechanics and orthopedic disorders exhibited by obese children, this dissertation sought to first, establish the proper methods to adequately quantify the necessary biomechanical measures in obese and healthy-weight individuals, and second, determine the effects of obesity and duration on muscle function and tibiofemoral loading during walking in children. The accuracy of muscle and joint contact forces estimated from dynamic musculoskeletal simulations is dependent upon the experimental kinematic data used as inputs. Subcutaneous adipose tissue makes the measurement of representative kinematics from motion analysis particularly challenging in overweight and obese individuals. We developed an obesity-specific kinematic marker set and methodology that accounted for subcutaneous adiposity. Next, we determined how this methodology affected muscle and joint contact forces predicted from musculoskeletal simulations of walking in obese individuals. The marker set methodology had a significant effect on model quantified lower-extremity kinematics, muscle forces, and hip and knee joint contact forces. We demonstrated the need for biomechanists to account for subcutaneous adiposity during kinematic data collection and proposed a feasible solution that likely improves the accuracy of musculoskeletal simulations in overweight and obese people. Understanding orthopedic disorders of biological and prosthetic knee joints requires knowledge of the in-vivo loading environment during activities of daily living. Anthropometric and orthopedic differences between individuals make accurate predictions from generic musculoskeletal models a challenge. We developed a knee mechanism within a full-body OpenSim musculoskeletal model that incorporated subject-specific knee parameters to predict medial and lateral tibiofemoral contact forces. To assess the accuracy of our model, we compared measured to predicted medial and lateral compartment contact forces during walking in an individual with an instrumented knee replacement. We determined the importance of specifying subject-specific tibiofemoral alignment and contact locations and validated a simple approach to measure and specify these parameters on a subject-specific basis using radiography. The biomechanical mechanisms responsible for the altered gait mechanics in obese children are not well understood. We investigated the relationship between adiposity and lower extremity kinematics, muscle force requirements, and individual muscle contributions to whole body dynamics by generating musculoskeletal simulations of walking in a group of children with a range of adiposity. Body fat percentage was correlated with average knee flexion angle during stance and pelvic obliquity range of motion, as well as with relative vasti, gluteus medius and soleus force production. The functional demands and relative force requirements of the hip abductors during walking in pediatric obesity likely contribute to the altered gait mechanics in obese children. The combination of larger magnitude and altered application of tibiofemoral loads during physical activity in obese children is commonly theorized to contribute to their increased risk of orthopedic disorders of the knee, such as growth-plate suppression leading to conditions of malalignment. To evaluate this theory and determine how prolonged activity affects knee loading, we quantified the effects of pediatric obesity and walking duration on medial and lateral tibiofemoral contact forces. We found that obese children have elevated medial compartment magnitudes, loading rates, and load share, which further increased with walking duration. The altered tibiofemoral loading environment during walking in obese children likely contributes to their increased risk of knee pain and pathology. These risks may increase with activity duration. This dissertation provides a foundation for improved understanding of the effects of pediatric obesity on the neuromuscular and musculoskeletal systems during walking. The main research outcomes from this dissertation aim to improve rehabilitation and activity guidelines that minimize the risk of musculoskeletal pain and pathology in obese children, address degenerative gait mechanics, and assist in breaking the cycle of weight gain

Musculoskeletal Modeling Analysis of Knee Joint Loading During Uphill and Downhill Waling In Patients with Total Knee Replacement

The purposes of these studies were to determine differences in total (TCF), medial (MCF) and lateral (LCF) tibiofemoral compartment compressive forces and related muscle forces between limbs (replaced, non-replaced, and control), and different slopes during uphill [0° (level), 5°, 10°], and downhill [0° (level), 5° 10°] using statistical parametric mapping (SPM). Static optimization was used to determine muscle and compressive forces for 9 patients with total knee arthroplasty (TKA) and 9 control participants during walking trials. Total , loading-response, and push-off TCF impulse were calculated. A 3×3 [Limb (replaced, non-replaced, control] × Slope (0°, 10°, 15°)] SPM[F] repeated measures ANOVA was conducted independently for both uphill and downhill walking. Independent 3×3 (Limb × Slope]) mixed-model ANOVA were used to detect differences for TCF impulse for both up- and downhill walking. For study one, significant between-limb differences were observed for MCF during 23-30% stance between replaced and control limbs. Significant differences between slopes were observed for all variables, except knee flexor muscle force. TCF impulse indicates that joint load is greater for all limbs as slope increases. A small sample size of patients with TKA who utilize different gait strategies may have rendered difference between limbs non-significant. For study two, significant differences were found for TCF, MCF, and knee flexor muscle forces between replaced and control limbs during early loading-response (1‑5% stance). No significant differences were found between limbs for MCF or LCF, suggesting that TKA may have been successful in correcting errant frontal plane alignment. Loading-response TCF impulse increased with increasing slope yet push-off TCF impulse decreased with increasing decline slope suggesting decreased knee joint loading during push-off while not having to overcome gravity. Uphill walking may be an effective exercise for high intensity early and long-term rehabilitation programs with increased muscular demand and quadriceps strengthening as slope increases while promoting the reacquisition of normal gait patterns following TKA. Downhill walking facilitates increased muscular demand and quadriceps strengthening via eccentric contractions while regaining normal gait patterns following TKA. Downhill walking, therefore, may be an effective exercise for high intensity early and long-term rehabilitation