Ankle-Foot Orthoses (AFOs) can be used for walking while offloading the lower limb, by transferring the ground reaction force (GRF) to a shank brace. The walking pattern obtained using an AFO is closer to natural gait than using crutches and offers various advantages for the rehabilitation process. However, to date, no AFO exists that allows accurate control over the amount of loading transferred to the foot. Here, we develop a new AFO that preserves the natural walking pattern while allowing accurate adjustment of the amount of foot loading between 0-100%. Our AFO contains a patient-specific 3D-printed brace and a topology-optimized skeleton, as well as an adjustable loading mechanism. We study the effect of the new AFO on foot loading and gait dynamics using instrumented pressure insoles, force plates, and a full-body motion capture system. This device has the potential to improve ankle-foot rehabilitation and offer personalized treatment for optimal outcomes.