Systems and methods are described that relate to the control of a powered lower limb assistive device with one or more joints, where a controller of the assistive device is configured to receive one or more user-generated signals, determine control information using information in the one or more user-generated signals, select one or more joint impedance parameters of the assistive device for adjustment, and, for a mode and state of the assistive device, adjust the selected joint impedance parameters as a function of the control information. Additionally, systems and methods are described that relate to the control of such an assistive device, where a controller of the assistive device is configured to receive one or more user-generated signals containing information about the ankle angle of the assistive device, and adjust the stiffness of the ankle joint of the assistive device as a function of the ankle angle.