The effect of different mechanism combinations on sliding between brace and lower limb during walking and leg-raising.

Knee braces are commonly used to support the knee joint and improve function. However, brace sliding caused by the misalignment between brace and knee during motion is a common problem, which reduces the therapeutic effect and leads to brace abandonment. To investigate the effect of mechanism combinations on sliding, an experimental brace was designed to isolate the mechanism as the sole variable. Ten healthy participants were recruited, each of whom worn four combinations of lateral/medial mechanisms: lateral and medial single-axis (SA), lateral super gear (SG) and medial non-circular gear (NCG), lateral four-bar linkage (FL) and medial SG, and lateral FL and medial NCG. The knee flexion angle was collected using inertial measurement units, and brace sliding was measured by 3D motion capture system. All combinations had significant changes in peak sliding of thigh and shank compared to the SA combination (p < 0.05), but lateral FL and medial NCG combination had the lowest peak and final sliding during walking and leg-raising, with significant reductions of 40.7 and 85.3% in peak sliding of thigh, and significant reductions of 56.3 and 72.0% in peak sliding of shank, respectively (p < 0.05). Moreover, the mechanism combination did not significantly impact the knee range of motion (p > 0.05). The mechanism combination that fit the instantaneous center of rotation of lateral/medial condyle of knee joint demonstrates a significant reduction in brace sliding. Additionally, the peak sliding during motion is significantly higher than the final sliding.

An interaction model for predicting brace migration and validation through walking experiment.

Brace migration undermines therapeutic efficacy, which is traditionally evaluated through walking experiments. This study developed an interaction model that considered the instantaneous center of rotation (ICR) misalignment to predict migration. The model was validated by walking experiment. Results show a strong positive correlation for four-linkage (FL) (r = 0.952, p < 0.01, root mean squared error (RMSE) = 0.53 mm) and spur gear (SG) (r = 0.898, p < 0.01, RMSE = 1.35 mm) mechanisms. The FL exhibits lower migration than SG (p < 0.05). In conclusion, the interaction model accurately predicts migration, emphasizing the influence of mechanism on migration.

A subject-specific musculoskeletal model to predict the tibiofemoral contact forces during daily living activities.

Accurate prediction of tibiofemoral contact force (TFCF) during daily living activities is significant for understanding the initiation, progression, and treatment of knee osteoarthritis (KOA). However, the diversity of target activities, prediction accuracy, and computational efficiency of the current musculoskeletal simulations need to be further improved. In this study, a subject-specific musculoskeletal model considered the tibiofemoral alignment, medial-lateral contact locations, secondary tibiofemoral and all patellofemoral motions, and knee ligaments was proposed to predict the TFCFs during the five daily activities (normal walking, sit-to-stand, stand-to-sit, stair ascent, and stair descent) in OpenSim software. The standing lower-limbs-full-length radiograph, local radiograph of knee joint, motion capture data, and force plate data of eighteen subjects were acquired as the input data of the musculoskeletal model. The results showed good agreements of TFCFs between the predictions based on our proposed musculoskeletal model and the in-vivo measurements based on instrumented knee implants during the five daily activities (RMSE: 0.16 ∼ 0.31 BW, R2: 0.88 ∼ 0.97, M: -0.11 ∼ -0.02, P: 0.03 ∼ 0.10, and C: 0.04 ∼ 0.14). Additionally, the order of the peak total and lateral TFCFs from low to high was normal walking, stair ascent and stand-to-sit, and stair descent and sit-to-stand (P < 0.05), and the peak medial TFCF was stand-to-sit, sit-to-stand, normal walking, stair ascent and stair descent (P < 0.05). The outcomes of this study are valuable for further understanding the knee biomechanics during daily living activities and providing theoretical guidance for the treatments of KOA.

Effect of fatigue on kinematics, kinetics and muscle activities of lower limbs during gait.

Muscle fatigue, as a serious social problem, affects the performance of daily living activities, especially for workers. Decrease of movement control ability caused by muscle fatigue is one of the risk and intrinsic factors for occupational accidents, such as slips, trips, falls, etc. In order to reduce the accident rate and optimize the existing prevention measures, it is necessary to investigate the effect of fatigue on kinematics, kinetics, and muscle activities of human body. In this paper, 26 healthy participants were recruited. The kinematics and kinetics analysis of lower limb joints, and surface electromyograms (sEMG) time-domain and frequency-domain analysis of lower limb periarticular muscles were utilized to investigate the effects of muscle fatigue. The results showed that the fatigue reduced the range-of-motion (RoM) of the lower limb joints. Smaller plantarflexion, knee flexion and hip flexion angles, and greater dorsiflexion angles were observed after fatigue. For the joint moment, the fatigue did not alter the joint moments except for the smaller knee flexion moment. For the joint power, the fatigue decreased the generation power of ankle, knee and hip joint and the absorption power of ankle and knee joints, whereas increased the absorption power of hip joint. Besides, the fatigue increased the normalized integrated sEMG (iEMG) and root-mean-square (RMS) of sEMG, and shifted the median frequency (MF) and mean power frequency (MPF) of sEMG toward lower frequencies. The results from the present study concluded that the muscle fatigue changed the kinematics, kinetics and muscle activities of lower limbs during gait, and then could increase the risk rate of occupational accidents.

Biomechanical Effect of Valgus Knee Braces on the Treatment of Medial Gonarthrosis: A Systematic Review.

Background: Valgus braces are prescribed as a common conservative treatment option for patients with medial gonarthrosis to improve their quality of life. Many studies had reviewed the effects of the valgus braces on patients with medial gonarthrosis, while they mainly focused on the knee adduction moment (KAM), with less attention paid to other parameters such as spatiotemporal and morphological parameters. Objectives: The purpose of this study was to review the effects of valgus braces on the spatiotemporal, kinematic/kinetic, morphological, and muscle parameters. Methods: Based on the selected keywords, a survey of literatures was performed in Web of Science, PubMed, Scopus, and Google Scholar using the PRISMA methods, and the search period was established from January 2000 to March 2022. Results: Thirty-four articles were included. According to the conclusion of these articles, the valgus brace can be used to relieve the symptoms of patients with medial gonarthrosis by decreasing the varus angle, decreasing the KAM, and redistributing the knee compartment loads. However, the effects of valgus braces on other biomechanical parameters (e.g., walking speed, cadence, joint angle, and joint space) had not reached a consensus. Conclusions: The valgus knee brace can effectively relieve the symptoms of medial gonarthrosis through multiple mechanisms, while there is still some confusion about the effectiveness of the valgus brace on the other biomechanical parameters.

The Impact of Team Knowledge Heterogeneity on Entrepreneurial Opportunity Identification: A Moderated Mediation Model.

PURPOSE: Due to the low success rate of entrepreneurship, the correct identification of entrepreneurial opportunities is one of the important concerns in the field of entrepreneurship research. Therefore, this study focuses on the influence mechanism of entrepreneurial opportunity identification, so as to enrich the influence path of entrepreneurial opportunity identification and provide suggestions for improving the success rate of entrepreneurship. METHODS: After screening and judging the quality of the questionnaires, the valid questionnaires were numbered and matched with 106 team samples. The researchers carried out telephone communication with participants to ask for their attendance, and then took samples on-site at the appointed time and place. RESULTS: The results show that: (1) team knowledge heterogeneity has a significant positive impact on entrepreneurial opportunity identification. (2) Social capital plays a mediating role between team knowledge heterogeneity and entrepreneurial opportunity identification. (3) Promotional regulatory focus, a type of regulation that tends to adopt a radical approach to achieve goals, positively moderates the mediating effect of team knowledge heterogeneity on entrepreneurial opportunity identification through social capital. However, preventive regulatory focus, a type of regulation that tends to adopt a cautious and vigilant way to achieve goals, has no moderating effect. DISCUSSION: In order to improve the correct identification of entrepreneurial opportunities, it is necessary to establish team with knowledge heterogeneity rationally and excavate different levels of social capital behind heterogeneous members. In addition, it also reveals that team style can retain certain promotive in the process of entrepreneurship, which is conducive to the feasibility and profitability of entrepreneurial opportunity identification.

A Comparison of Dynamic and Static Hip-Knee-Ankle Angle during Gait in Knee Osteoarthritis Patients and Healthy Individuals.

Malalignment of the lower limbs is the main biomechanical factor for knee osteoarthritis (KOA). The static hip-knee-ankle angle (S-HKAA) measured from radiograph is regarded as the "gold standard" of the malalignment. However, many evidences showed that the S-HKAA has no significant correlation with the knee dynamic-load distribution, unlike the dynamic HKAA (D-HKAA). The purpose of this study was to quantitatively analyze the D-HKAA and investigate the relationship between D-HKAA and S-HKAA for both KOA and healthy participants. In this paper, twenty-five healthy subjects and twenty-five medial compartment KOA (M-KOA) patients were recruited. Three-dimensional motion analysis and standing lower-limbs-full-length radiograph were utilized to obtain the D-HKAA and S-HKAA, respectively. The results showed that the mean D-HKAA was more varus than the S-HKAA (p < 0.05). For the mean D-HKAA, larger varus angle was observed in swing phase than stance phase (p < 0.05). Compared with healthy subjects, the M-KOA patients had remarkably smaller S-HKAA and D-HKAA during gait cycle (p < 0.01). For the relationship between the S-HKAA and mean D-HKAA, no significant correlation was found for both healthy subjects and M-KOA patients (r < 0.357, n = 25, p > 0.05, Spearman correlation analysis). In conclusion, the S-HKAA was limited to predict the D-HKAA for both M-KOA patients and healthy subjects. The D-HKAA should be given more attention to the orthopedist and the designer of knee brace and orthotics.

Knee Joint Biomechanics in Physiological Conditions and How Pathologies Can Affect It: A Systematic Review.

The knee joint, as the main lower limb motor joint, is the most vulnerable and susceptible joint. The knee injuries considerably impact the normal living ability and mental health of patients. Understanding the biomechanics of a normal and diseased knee joint is in urgent need for designing knee assistive devices and optimizing a rehabilitation exercise program. In this paper, we systematically searched electronic databases (from 2000 to November 2019) including ScienceDirect, Web of Science, PubMed, Google Scholar, and IEEE/IET Electronic Library for potentially relevant articles. After duplicates were removed and inclusion criteria applied to the titles, abstracts, and full text, 138 articles remained for review. The selected articles were divided into two groups to be analyzed. Firstly, the real movement of a normal knee joint and the normal knee biomechanics of four kinds of daily motions in the sagittal and coronal planes, which include normal walking, running, stair climbing, and sit-to-stand, were discussed and analyzed. Secondly, an overview of the current knowledge on the movement biomechanical effects of common knee musculoskeletal disorders and knee neurological disorders were provided. Finally, a discussion of the existing problems in the current studies and some recommendation for future research were presented. In general, this review reveals that there is no clear assessment about the biomechanics of normal and diseased knee joints at the current state of the art. The biomechanics properties could be significantly affected by knee musculoskeletal or neurological disorders. Deeper understanding of the biomechanics of the normal and diseased knee joint will still be an urgent need in the future.