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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.