Purpose: This study aimed to investigate the biomechanical effects of a center bridge-type knee orthosis prescribed for patients with knee osteoarthritis (OA) based on real-time, direct quantification of external knee adduction moment (EKAM), a key mechanical indicator associated with progression of knee OA. Patients and Methods: To evaluate the effect of the center bridge-type knee orthosis, 17 patients with knee OA performed level-ground walking under two conditions: with and without the orthosis. Each participant completed gait trials in both conditions in a randomized order. Additionally, 18 healthy older individuals were assessed during free walking for comparisons. The analysis focused on the gait stance phase, during which substantial mechanical loading was exerted on the knee joint. Gait data were obtained using a six-axis force-torque sensor. Results: In patients with knee OA, wearing the orthosis significantly reduced EKAM during the loading response compared with that in the no-orthosis condition. Furthermore, EKAM values in patients wearing the orthosis became comparable to those in healthy participants during the loading response and pre-swing phases. No significant differences in gait parameters, such as walking speed or stride length, were observed between groups or conditions. Conclusion: These findings suggest that in patients with OA, achieving EKAM values comparable to those in healthy individuals would require a valgus corrective moment at least 5.34 times greater than that produced by the center bridge-type knee orthosis. Clinically, this indicates that current orthotic designs may provide insufficient mechanical offloading, and that further structural refinements are required to enhance valgus correction and achieve more effective reduction of medial knee loading during gait. Plain Language Summary: In knee osteoarthritis, the joint cartilage breaks down, resulting in knee pain, swelling, and stiffness. External knee adduction moment (EKAM) is a biomechanical indicator of medial knee loading during walking. Measuring EKAM is useful for assessing disease progression. In this study, we evaluated a center bridge-type knee orthosis designed to reduce medial knee load and improve gait. A total of 17 patients with knee osteoarthritis and 18 healthy adults participated. Each participant performed level-ground walking with and without the orthosis, while the support provided by the device was quantified in real time using a built-in six-axis force sensor. The orthosis significantly reduced EKAM during the loading response, with values approaching those of healthy individuals. Furthermore, during pre-swing, when the foot prepares to leave the ground for the next step, medial knee loading was also close to healthy levels. However, gait parameters such as walking speed and stride length showed no significant differences between groups or conditions. These findings indicate that the orthosis provides substantial mechanical support during the early stance phase and continues to reduce medial knee loading even during the transition to swing. Nevertheless, to fully normalize EKAM throughout the stance phase, a corrective force that gently pushes the knee outward and is approximately five-fold stronger than what the current orthosis can generate would be required. These insights will guide the development of future knee orthoses capable of adjusting support dynamically throughout walking. Keywords: valgus corrective moment, walking biomechanics, force-torque sensor, loading response, stance phase
Nakano et al. (Sun,) studied this question.