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The attachment locations of anterior cruciate ligament (ACL) grafts during reconstruction have been reported to influence knee joint function. However, there are controversial opinions on femoral ACL attachment locations for restoring normal knee kinematics. The knee stability and ACL force by different ACL attachment locations could be predicted using the musculoskeletal model simulation. The objectives of this study are to develop a detailed musculoskeletal knee model and to quantify the effect of ACL graft attachment locations on knee kinematics and graft force. Five normal subjects walked at a self-selected speed, and motion data were captured. A detailed knee model including 14 ligaments was developed for dynamics simulation using cadaveric specimen data, which were previously published and are open to public access. The ACL bundles of the model were removed and replaced with ACL grafts to develop anatomical and isometric ACL-reconstructed knee models; the femoral anatomical footprint and isometric locations were used, respectively. After the knee models were embedded in a full-body template model from the AnyBody Managed Model Repository, the full-body musculoskeletal model was simulated using the measured gait data. The isometric reconstruction model had significantly large anterior translation and internal rotation than the intact and anatomical reconstruction model. The average differences between the isometric reconstruction and intact models were 4.5 mm and 3.0° for tibial anterior translation and internal rotation, respectively. The ACL tensional force in the isometric reconstruction model was significantly lower than that in the intact model. Anatomical reconstruction could closely restore the normal knee kinematics.

Injuries in the anterior cruciate ligament (ACL), including partial tear and lengthening of the ACL, change the dynamic function of the knee. However, there is a lack of information on the effect of ACL partial tear on knee kinematics during walking. This study aimed to investigate the effects of different levels of ACL injuries on knee stability and ACL tensional force to identify the critical injury level. Motion data of five normal subjects were acquired along with the ground reaction force. A knee model with 14 ligaments was developed using cadaveric specimen data. The initial length and stiffness of the ACL were changed to develop ACL-injured knee models. Musculoskeletal simulations of the knee models were performed using the measured gait data. The average tibial anterior translation increased significantly by 2.6 ± 0.7 mm when the ACL stiffness decreased to 25% of its original stiffness. The average tibial anterior translation increased significantly by 2.6 ± 0.3 mm at an increase in initial length of 10%. The knee with partial ACL tear had a nonlinear decrease in ACL forces owing to the increase in the level of ACL injury, while the knee with ACL lengthening had linear decreased ACL forces. The partial tear of the ACL caused translational instability, while the complete tear caused both rotational and translational instabilities during the musculoskeletal walking simulation. This study presents the effects of partial ACL injuries on joint kinematics and ACL tensional force during the dynamic motion of walking.

Chronic occupational lower limb injuries such as osteoarthritis require an understanding of mechanical loading conditions in joints during occupational activities. We aimed to develop a human musculoskeletal model and to estimate knee contact force and ground reaction force (GRF) simultaneously during walking and squatting. GRF and joint kinematics were obtained from a subject with electronic total knee replacement during walking and squatting. Force reaction elements were embedded in the knee and foot of a full-body musculoskeletal model. The joint kinematics and ground vertical force were applied to the musculoskeletal model to estimate ground shear force and knee contact force using an inverse dynamics-based optimization. Ground shear force and knee contact force could be estimated simultaneously with root mean square (RMS) error less than 1.6% body weight (BW) and 35% BW, respectively. Simultaneous estimations could be accurately conducted but the RMS error for the knee contact force increased by approximately 10% BW.

Accurate joint kinematics plays an important role in estimating joint kinetics in musculoskeletal simulations. Biplanar fluoroscopic (BPF) systems have been introduced to measure skeletal kinematics with six degrees-of-freedom. The purpose of this study was to model knee kinematic coupling using knee kinematics during walking, as measured by the BPF system. Seven healthy individuals (mean age, 23 ± 2 yr) performed treadmill walking trials at 1.2 m/s. Knee kinematics was regressed separately for the swing and stance phases using a generalized mixed effects model. Tibial anterior translation function was y=0.20x−3.09 for the swing phase and y=0.31x−0.54 for the stance phase, where x was the flexion angle and y was the tibial anterior translation. Tibial lateral and inferior translation were also regressed separately for the stance phase and the swing phase. Tibial external rotation was y=−0.002x2+0.19x−0.64 for the swing phase and y=−0.19x−1.22 for the stance phase. The tibial adduction rotation function was also calculated separately for the stance and swing phase. The study presented three-dimensional coupled motion in the knee during the stance and swing phases of walking, and demonstrated the lateral pivoting motion found in previous studies. This expanded understanding of secondary knee motion functions will benefit musculoskeletal simulation and help improve the accuracy of calculated kinetics.

Background Although pedobarographic measurement is increasingly used for clinical and research purposes, relatively few published studies have investigated normative data. This study examined pedobarographic findings in young healthy adults with regard to sex-related differences and correlations among measurement indices. Methods Twenty young healthy adults (mean age, 22.4 years; standard deviation, 1.2 years; and 10 males and 10 females) were included. Weight bearing anteroposterior (AP) and lateral foot radiographs were taken, and dynamic pedobarographic data during treadmill walking and maximum ankle dorsiflexion were obtained. AP talo-first metatarsal angle, naviculocuboid overlap, lateral talo-first metatarsal angle, and plantar soft tissue thickness were measured on foot radiographs. Pedobarographic data including peak pressure and pressure-time integral were measured on five plantar segments: medial forefoot (MFF), lateral forefoot (LFF), medial midfoot (MMF), lateral midfoot (LMF), and heel. Results Male and female subjects significantly differed in body mass index (BMI, p < 0.001), AP talo-first metatarsal angle (p = 0.018), soft tissue thickness under the metatarsal head (p = 0.040) and calcaneal tuberosity (p < 0.001), maximum dorsiflexion during stance phase (p = 0.041), peak pressure on the MFF (p = 0.005) and LFF (p = 0.004), and pressure-time integral on the MFF (p = 0.018) and heel (p = 0.001). BMI was significantly correlated with soft tissue thickness under the metatarsal head (r = 0.521, p = 0.018) and calcaneal tuberosity (r = 0.585, p = 0.007), peak pressure on the MFF (r = 0.601, p = 0.005) and LFF (r = 0.487, p = 0.029), pressure-time integral on the heel (r = 0.552, p = 0.012), and total pressure-time integral (r = 0.755, p < 0.001). Maximum dorsiflexion demonstrated significant negative correlations with pressure-time integral on the MFF (r = −0.595, p = 0.007) and total pressure-time integral (r = −0.492, p = 0.032). Pressure-time integral varus/valgus index was significantly correlated with pressuretime integral forefoot/heel index (r = 0.472, p = 0.036). Conclusions Sex-related differences in pedobarographic examination were observed, which could provide useful information in setting appropriate treatment goals and obtaining appropriate control data. The effects of subtalar motion in distributing plantar pressure should be investigated in a future study.