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The estimation of joint contact forces in musculoskeletal multibody dynamics models typically requires the use of expensive and time-consuming technologies, such as reflective marker-based motion capture (Mocap) system. In this study, we aim to propose a more accessible and cost-effective solution that utilizes the dual smartphone videos (SPV)-driven musculoskeletal multibody dynamics modeling workflow to estimate the lower limb mechanics. Twelve participants were recruited to collect marker trajectory data, force plate data, and motion videos during walking and running. The smartphone videos were initially analyzed using the OpenCap platform to identify key joint points and anatomical markers. The markers were used as inputs for the musculoskeletal multibody dynamics model to calculate the lower limb joint kinematics, joint contact forces, and ground reaction forces, which were then evaluated by the Mocap-based workflow. The root mean square error (RMSE), mean absolute deviation (MAD), and Pearson correlation coefficient (ρ) were adopted to evaluate the results. Excellent or strong Pearson correlations were observed in most lower limb joint angles (ρ = 0.74 ~ 0.94). The averaged MADs and RMSEs for the joint angles were 1.93 ~ 6.56° and 2.14 ~ 7.08°, respectively. Excellent or strong Pearson correlations were observed in most lower limb joint contact forces and ground reaction forces (ρ = 0.78 ~ 0.92). The averaged MADs and RMSEs for the joint lower limb joint contact forces were 0.18 ~ 1.07 bodyweight (BW) and 0.28 ~ 1.32 BW, respectively. Overall, the proposed smartphone video-driven musculoskeletal multibody dynamics simulation workflow demonstrated reliable accuracy in predicting lower limb mechanics and ground reaction forces, which has the potential to expedite gait dynamics analysis in a clinical setting. [ABSTRACT FROM AUTHOR]

Osteoporosis results in low-trauma fractures affecting millions globally, in particular elderly populations. Despite the inclusion of physical activity in fracture prevention strategies, the optimal bone-strengthening exercises remain uncertain, highlighting the need for a deeper understanding of lower limb joint loading dynamics across various exercise types and levels. This study examines lower limb joint loading during high-impact exercises across different intensities. A total of 40 healthy, active participants were recruited (mean ± SD: age of 40.3 ± 13.1 yr; height 1.71 ± 0.08 m; and mass 68.44 ± 11.67 kg). Motion capture data and ground reaction forces of 6 different exercises: a self-selected level of walking, running, countermovement jump, squat jump, unilateral hopping, and bilateral hopping were collected for each participant. Joint reaction forces were estimated using lower body musculoskeletal models developed in OpenSim. Running and hopping increased joint forces compared to walking, notably at the hip (83% and 21%), knee (134% and 94%), and ankle (94% and 77%), while jump exercises reduced hip and ankle loading compared to walking (36% and 19%). Joint loading varied with exercise type and intensity, with running faster increasing forces on all joints, particularly at the hip. Sprinting increased forces at the hip but lowered knee and ankle forces. Higher jumps intensified forces on all joints, while faster hopping reduced forces. The wide variation of lower limb joint loading observed across the exercises tested in this study underscores the importance of implementing diverse exercise routines to optimize overall bone health and strengthen the musculoskeletal structure. Practitioners must therefore ensure that exercise programs include movements that are specifically suitable for their intended purpose. Lay Summary: Osteoporosis is a global health concern, particularly among the elderly, leading to increased risk of fractures. Although physical activity is recommended to prevent fractures, the most effective bone-strengthening exercises remain unclear. This study aimed to quantify how different high-impact exercises affect lower limb joint loading dynamics. Forty healthy, active participants with an average age of 40 yr performed 6 exercises: walking, running, jumping, and hopping, at various intensities. Motion capture technology and computational modeling were used to analyze joint forces at the hip, knee, and ankle. Results showed that running and hopping increased joint forces compared to walking, particularly at the hip and knee. Conversely, jumping exercises reduced hip and ankle loading. Joint loading varied across exercise types and intensities; for example, running faster increased forces primarily on the hip, while jumping higher increased forces on all joints. Conversely, faster hopping reduced forces. These findings highlight the importance of incorporating diverse exercises into bone-strengthening routines to optimize overall bone health and musculoskeletal strength. Healthcare practitioners should tailor exercise programs to individual needs, ensuring they include appropriate movements for desired outcomes. Graphical Abstract [ABSTRACT FROM AUTHOR]

Toe-in gait is a pathology in which the child walks and turns the foot inward instead of pointing straight ahead. The alignment of the lower limb structure changes in this disease, increasing the incidence of knee and hip osteoarthritis. This study aimed to determine the kinematic and joint loading in subjects walking with a toe-in gait pattern. This study selected two groups of subjects: normal subjects and those with toe-in gait due to an increased femoral head anteversion angle (each group consisted of 15 subjects). A Qualisys motion analysis system and a Kistler force plate were used to record the motions and forces applied to the leg while walking. OpenSim software (version 3.3) was used to analyze the range of motion, moments, muscle forces, and joint contact forces in both groups of subjects. The mean values of stride length for normal subjects (1.1 ± 0.141 m) and those with toe-in gait (0.94 ± 0.183 m) differed significantly. The mediolateral component of the ground reaction force decreased significantly in the toe-in gait group compared to normal subjects (p -value = 0.05). The peak force of most of the hip joint muscles increased significantly in those with toe-in gait compared to normal subjects (p -value < 0.05). The results of this study showed that those with toe-in gait, due to an increase in femoral head anteversion angle, only had a change in rotation of the pelvic and hip joint. There was no significant difference between walking speed and most ground reaction force components between normal subjects and those with toe-in gait. As the peaks of most of the hip joint muscles increased significantly in the toe-in gait group, this increased joint contact forces (especially the anteroposterior component of the hip joint and the mediolateral component of the knee joint), which may ultimately increase the incidence of hip and knee joint osteoarthritis. [ABSTRACT FROM AUTHOR]

Cerebral palsy (CP) includes a group of neurological conditions caused by damage to the developing brain, resulting in maladaptive alterations of muscle coordination and movement. Estimates of joint moments and contact forces during locomotion are important to establish the trajectory of disease progression and plan appropriate surgical interventions in children with CP. Joint moments and contact forces can be estimated using electromyogram (EMG)-informed neuromusculoskeletal models, but a reduced number of EMG sensors would facilitate translation of these computational methods to clinics. This study developed and evaluated a muscle synergy-informed neuromusculoskeletal modelling approach using EMG recordings from three to four muscles to estimate joint moments and knee contact forces of children with CP and typically developing (TD) children during walking. Using only three to four experimental EMG sensors attached to a single leg and leveraging an EMG database of walking data of TD children, the synergy-informed approach estimated total knee contact forces comparable to those estimated by EMG-assisted approaches that used 13 EMG sensors (children with CP, n = 3, R2 = 0.95 ± 0.01, RMSE = 0.40 ± 0.14 BW; TD controls, n = 3, R2 = 0.93 ± 0.07, RMSE = 0.19 ± 0.05 BW). The proposed synergy-informed neuromusculoskeletal modelling approach could enable rapid evaluation of joint biomechanics in children with unimpaired and impaired motor control within a clinical environment. [ABSTRACT FROM AUTHOR]

Purpose: Toe-in gait is defined as a style of walking in which the foot turns inward. It may be caused by an increase in femoral bone anteversion, tibia torsion, and metatarsus adductus. There are some conservative treatment approaches used to correct this condition. This review aimed to determine the effects of the toe-in gait on joint loading, kinematics, and kinetic parameters while walking. Moreover, it sought to determine the efficiency of various conservative treatments used to correct the condition. Materials and Methods: A literature search was conducted in the following databases: PubMed, Institute for Scientific Information (ISI), Web of Science database, EBSCO, and Embase, using the following keywords in toe, toe-in, toeing, in-toe, pigeon toe, and conservative treatment published between 1950 and 2021. The quality of the studies was evaluated using the Down and Black tool. Results: A total of 13 papers on the impact of toe-in gait on joint contact force, kinematics, kinetic parameters, and conservative approaches to management were found. The quality of the studies varied between a score of 11 and 22. The toe-in gait influences the joint contact forces and kinematics of the joints, especially the hip and pelvis. The effects of conservative treatment on the toe-in gait appear to be controversial. Conclusion: As the toe-in gait influences the joint contact force, it may increase the incidence of degenerative joint diseases. Therefore, treatment is recommended. However, there is no strong evidence on the efficacy of conservative treatments, and there are no recommendations for the use of these treatments in subjects with toe-in gait. [ABSTRACT FROM AUTHOR]

Joint contact force is the actual force applied on the articular surface that could predict performance and injuries, but rarely reported for badminton sport. The study sought to calculate lower limb joint contact force and decelerative kinematics for badminton forward lunges. Fifteen badminton players performed backhand and forehand forward lunges in random order. The kinematic and kinetic data were input to scale a musculoskeletal model and solve inverse dynamics in the simulations. Outcome variables were compared between lunge conditions using repeated measures MANOVA. Forehand lunge produced higher compressional ankle contact force (p = 0.040, partial η2 = 0.14), faster touchdown hip abduction (p = 0.031, partial η2 = 0.16), and larger horizontal deceleration of the mass centre (p = 0.016, partial η2 = 0.19) and torso (p = 0.031, partial η2 = 0.16) compared to backhand lunge. Despite the statistical significance, we found that the increments of joint loading in forehand lunge were small (<5%) with limited effect size and could be attributed to the larger movement deceleration during braking. These force changes could possess performance merits. However, its linkage to injury risk is unclear and warrants further investigation. [ABSTRACT FROM AUTHOR]

Background: Previous studies on different periacetabular osteotomy approaches for correction of hip dysplasia disagree on the time course of normalisation of muscle function postoperatively, some stating that especially hip flexor function is not fully normalised after 12 months. Purpose: The purpose of this study was to evaluate hip function during walking before, and 6 and 12 months after minimally invasive periacetabular osteotomy. Methods: Using conventional 3D inverse dynamics followed by static optimisation, we calculated hip net joint moment and angular impulse, as well as individual muscle forces and hip joint contact force, during walking for 32 patients with hip dysplasia and 32 matched controls. Results: None of the extensor and abductor measures were significantly different between controls and patients tested preoperatively, nor between any of the 3 time points patients were tested. For all of the flexor measures, patients' preoperative values were lower than controls', but had increased to values above the controls 6 months postoperatively. Conclusion: Hip muscle function during walking seemed normalised after 6 months after minimally invasive periacetabular osteotomy, while joint contact force did not fully normalise until 12 months postoperatively, perhaps because the hip joint structures need a longer time to heal than the muscles and a potential pain alleviating strategy was still in effect. Trial registry: Movement pattern in patients with hip dysplasia https://clinicaltrials.gov/ct2/show/NCT01344421, NCT01344421. [ABSTRACT FROM AUTHOR]

Back squats are a common strengthening exercise for knee and hip musculature. However, repetitive loaded movements like backs squats result in high patellofemoral joint loading and therefore may contribute to the development of common overuse injuries. Thus, it is important to understand how changing parameters such as squat depth or load influences patellofemoral loading. This study investigated differences in patellofemoral loading when experienced female lifters squatted to three depths (above parallel, parallel, and below parallel) and with three loads (unloaded, 50%, and 85% of depth-specific one repetition maximums). Patellofemoral joint reaction forces (pfJRF) and stresses (pfJS) were calculated from biomechanical models incorporating knee extensor moments (KEM) and joint angles. Peak KEMs displayed a depth-by-load interaction such that within each depth, as load increased so did peak KEM. However, within each load, the effects of depth were different. Peak pfJRF also increased with load and was higher at below parallel than above or parallel depths. Peak pfJS also displayed a depth-by-load interaction, increasing with load within a given depth, and being greatest at the below parallel depths within a given load. If patellofemoral joint loading is a concern, clinicians or coaches should carefully monitor the depth and load combinations being used. [ABSTRACT FROM AUTHOR]

Gait biomechanics after anterior cruciate ligament (ACL) injury are associated with functional outcomes and the development of posttraumatic knee osteoarthritis. However, biomechanical outcomes between patients treated nonoperatively compared with operatively are not well understood. The primary purpose of this study was to compare knee joint contact forces, angles, and moments during loading response of gait between individuals treated with operative compared with nonoperative management at 5 years after ACL injury. Forty athletes treated operatively and 17 athletes treated nonoperatively completed gait analysis at 5 years after ACL reconstruction or completion of nonoperative rehabilitation. Medial compartment joint contact forces were estimated using a previously validated, patient‐specific electromyography‐driven musculoskeletal model. Knee joint contact forces, angles, and moments were compared between the operative and nonoperative group using mixed model 2 × 2 analyses of variance. Peak medial compartment contact forces were larger in the involved limb of the nonoperative group (Op: 2.37 ± 0.47 BW, Non‐Op: 3.03 ± 0.53 BW; effect size: 1.36). Peak external knee adduction moment was also larger in the involved limb of the nonoperative group (Op: 0.25 ± 0.08 Nm/kg·m, Non‐Op: 0.32 ± 0.09 Nm/kg·m; effect size: 0.89). No differences in radiographic tibiofemoral osteoarthritis were present between the operative and nonoperative groups. Overall, participants treated nonoperatively walked with greater measures of medial compartment joint loading than those treated operatively, while sagittal plane group differences were not present. Statement of clinical relevance: The differences in medial knee joint loading at 5 years after operative and nonoperative management of ACL injury may have implications on the development of posttraumatic knee osteoarthritis. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to examine the joint contact forces (JCF) between each limb as the LLD magnitude increases during walking activity. Methods: Eighteen male healthy subjects volunteered to participate in the experiment. Walking gait analysis was conducted with eight different levels of insole to simulate the LLD, starting from 0 cm until 4.0 cm with 0.5 cm increment. Qualisys Track Manager System and C-motion Visual 3D biomechanical tools were used to analyse the results. Four joints (ankle, knee, hip, and pelvis) of lower limb of two legs were investigated. The increment of insoles was placed on the right leg to represent the long leg. Results: The results suggest that the mean contact forces for all joints in the short leg were increased as the increment level increased. On the contrary, the mean contact forces in the long leg decreased when the LLD level increased. Among these four joints, JCF in hip shows a positive increment based on the ASI value. Means that hip shows the most affected joint as the LLD level increase. Conclusions: The result obtained in this study might help clinicians treat patients with a structural LLD for treatment plan including surgical intervention. [ABSTRACT FROM AUTHOR]

Knee osteoarthritis is a major public health problem and adults with obesity are particularly at risk. One approach to alleviating this problem is to reduce the mechanical load at the joint during daily activity. Adjusting temporospatial parameters of walking could mitigate cumulative knee joint mechanical loads. The purpose of this study was to determine how adjustments to velocity and step length affects knee joint loading in healthy weight adults and adults with obesity. We collected three‐dimensional gait analysis data on 10 adults with a normal body mass index and 10 adults with obesity during over ground walking in nine different conditions. In addition to preferred velocity and step length, we also conducted combinations of 15% increased and decreased velocity and step length. Peak tibiofemoral joint impulse and knee adduction angular impulse were reduced in the decreased step length conditions in both healthy weight adults (main effect) and those with obesity (interaction effect). Peak knee joint adduction moment was also reduced with decreased step length, and with decreased velocity in both groups. We conclude from these results that adopting shorter step lengths during daily activity and when walking for exercise can reduce mechanical stimuli associated with articular cartilage degenerative processes in adults with and without obesity. Thus, walking with reduced step length may benefit adults at risk for disability due to knee osteoarthritis. Clinical Significance: Adopting a shorter step length during daily walking activity may reduce knee joint loading and thus benefit those at risk for knee cartilage degeneration. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2679‐2686, 2018 [ABSTRACT FROM AUTHOR]

Background: Although there are a few studies on kinetic and kinematic parameters of scoliotic subjects, it is still controversial whether gait performance of scoliotic subjects differs from that of normal subjects or not. Moreover, there is lack of information regarding joint contact force of scoliotic on convex and concave sides. Therefore, this study examined these issues. Method: Two groups of children (healthy and children with scoliosis, each group consisting of 5 subjects) participated in this study. The force applied on leg and motions of body parts were evaluated using a Kistler force plate and motion analysis system, respectively. Joint contact forces, muscles length were evaluated in both groups and on both sides (in scoliotic subjects) with OpenSim software. The difference in the parameters between healthy children and scoliotic subjects, and also concave and convex sides, was determined using the independent t test. P value was set at ≤ 0. 0 5. Results: The results of this study showed that there was no difference between the forces applied on the leg, range of motions of the joints (hip, knee, ankle, pelvic and trunk), muscles length and joint contact force, neither between normal and children with scoliosis, nor between concave and convex sides (p > 0. 0 5). Conclusion: The findings revealed that scoliosis deformity with curve less than 4 0 ∘ does not have any significant effect on joint contact force, kinetic and kinematic parameters. [ABSTRACT FROM AUTHOR]

Our purpose was to compare joint loads between habitual rearfoot (hRF) and habitual mid/forefoot strikers (hFF), rearfoot (RFS) and mid/forefoot strike (FFS) patterns, and shorter stride lengths (SLs). Thirty-eight hRF and hFF ran at their normal SL, 5% and 10% shorter, as well as with the opposite foot strike. Three-dimensional ankle, knee, patellofemoral (PF) and hip contact forces were calculated. Nearly all contact forces decreased with a shorter SL (1.2–14.9% relative to preferred SL). In general, hRF had higher PF (hRF-RFS: 10.8 ± 1.4, hFF-FFS: 9.9 ± 2.0 BWs) and hip loads (axial hRF-RFS: −9.9 ± 0.9, hFF-FFS: −9.6 ± 1.0 BWs) than hFF. Many loads were similar between foot strike styles for the two groups, including axial and lateral hip, PF, posterior knee and shear ankle contact forces. Lateral knee and posterior hip contact forces were greater for RFS, and axial ankle and knee contact forces were greater for FFS. The tibia may be under greater loading with a FFS because of these greater axial forces. Summarising, a particular foot strike style does not universally decrease joint contact forces. However, shortening one’s SL 10% decreased nearly all lower extremity contact forces, so it may hold potential to decrease overuse injuries associated with excessive joint loads. [ABSTRACT FROM PUBLISHER]

A cohort of adult acquired flatfoot deformity rigid-body models was developed to investigate the effects of isolated tendon transfer with successive levels of medializing calcaneal osteotomy (MCO). Following IRB approval, six diagnosed flatfoot sufferers were subjected to magnetic resonance imaging (MRI) and their scans used to derive patient-specific models. Single-leg stance was modeled, constrained solely through physiologic joint contact, passive soft-tissue tension, extrinsic muscle force, body weight, and without assumptions of idealized mechanical joints. Surgical effect was quantified using simulated mediolateral (ML) and anteroposterior (AP) X-rays, pedobarography, soft-tissue strains, and joint contact force. Radiographic changes varied across states with the largest average improvements for the tendon transfer (TT) + 10 mm MCO state evidenced through ML and AP talo-1st metatarsal angles. Interestingly, 12 of 14 measures showed increased deformity following TT-only, though all increases disappeared with inclusion of MCO. Plantar force distributions showed medial forefoot offloading concomitant with increases laterally such that the most corrected state had 9.0% greater lateral load. Predicted alterations in spring, deltoid, and plantar fascia soft-tissue strain agreed with prior cadaveric and computational works suggesting decreased strain medially with successive surgical repair. Finally, joint contact force demonstrated consistent medial offloading concomitant with variable increases laterally. Rigid-body modeling thus offers novel advantages for the investigation of foot/ankle biomechanics not easily measured in vivo. [ABSTRACT FROM AUTHOR]

Although the conventional total knee arthoplasty (TKA) planning used 2D or 3D images of the patient’s lower extremity to determine bone alignment, it was shown that good bone alignment does not always guarantee successful results due to unbalanced joint contact forces and soft tissue tension. Thus, the joint contact force balance and soft tissue tension were pre-operatively calculated using finite element analysis (FEA). Although the results of FEA are accurate, the rigid body spring method (RBSM) has introduced for the joint contact force or pressure distribution due to the high costs for FEA. In this paper, an innovative method was described to quantify the pre- and post-operative knee contact force balance using various engineering techniques, including the free-form deformation (FFD) technique, and RBSM-based cartilage contact force and ligament tension estimation algorithm. Nine cases of TKA planning were performed with three different surgical options, including over-correction of the valgus ratio of the femur, tibial plateau cutting length, and MCL release to redistribute the medial and lateral contact force balance. This method is useful as a patient-specific preoperative planning tool in TKA surgery. [ABSTRACT FROM AUTHOR]

Musculoskeletal simulation software and model repositories have broadened the user base able to perform musculoskeletal analysis and have facilitated in the sharing of models. As the recognition of musculoskeletal modeling continues to grow as an engineering discipline, the consistency in results derived from different models and software is becoming more critical. The purpose of this study was to compare eight models from three software packages and evaluate differences in quadriceps moment arms, predicted muscle forces, and predicted tibiofemoral contact forces for an idealized knee-extension task spanning −125 to +10° of knee extension. Substantial variation among models was observed for the majority of aspects evaluated. Differences among models were influenced by knee angle, with better agreement of moment arms and tibiofemoral joint contact force occurring at low to moderate knee flexion angles. The results suggest a lack of consistency among models and that output differences are not simply an artifact of naturally occurring inter-individual differences. Although generic musculoskeletal models can easily be scaled to consistent limb lengths and use the same muscle recruitment algorithm, the results suggest those are not sufficient conditions to produce consistent muscle or joint contact forces, even for simplified models with no potential of co-contraction. [ABSTRACT FROM AUTHOR]

Typical inverse dynamics approaches to the calculation of muscle, ligament, and joint contact forces are based on a step-wise solution of the equations of motion. This approach is therefore limited in its ability to provide insight as to the muscular, ligamentous, and articular interactions that create joint stability. In this study, a new musculoskeletal model of the lower limb is described, in which the equations of motion describing the force and moment equilibrium at the joints of the lower limb are solved simultaneously using optimization techniques. The new model was employed to analyze vertical jumping using a variety of different optimization cost functions and the results were compared to more traditional approaches. The new model was able to find a solution with lower muscular force upper bounds due to the ability of the ligaments to contribute to moment equilibrium at the ankle and knee joints. Equally, the new model produced lower joint contact forces than traditional approaches for cases which also included a consideration as to ligament or joint contact forces within the cost function. This study demonstrates the possibility of solving the inverse dynamic equations of motion simultaneously using contemporary technology, and further suggests that this might be important due to the complementary function of the muscles and ligaments in creating joint stability. [ABSTRACT FROM AUTHOR]

Traditional inverse dynamics approaches to calculating the inter-segmental moments are limited in their ability to accurately reflect the function of the biarticular muscles. In particular they are based on the assumption that the net inter-segmental moment is zero and that total joint moments are independent of muscular activity. Traditional approaches to calculating muscular forces from the inter-segmental moments are based on a consideration of joint moments which do not encapsulate the potential moment asymmetry between segments. In addition, traditional approaches may artificially constrain the activity of the biarticular muscles. In this study, an optimization approach to the simultaneous inverse determination of inter-segmental moments and muscle forces (the 1-step method) based on a consideration of segmental rotations was employed to study vertical jumping and contrasted with the more traditional 2-step approach of determining inter-segmental moments from an inverse dynamics analysis then muscle forces using optimization techniques. The 1-step method resulted in significantly greater activation of both the monoarticular and biarticular musculature which was then translated into significantly greater joint contact forces, muscle powers, and inter-segmental moments. The results of this study suggest that traditional conceptions of inter-segmental moments do not completely encapsulate the function of the biarticular muscles and that joint function can be better understood by recognizing the asymmetry in inter-segmental moments. [ABSTRACT FROM AUTHOR]