A system and method associated with the movement of a limb. In one example, the system, such as a prosthetic or orthotic system, includes an actuator that actively controls, or adjusts, the angle between a foot unit and a lower limb member. The actuator preferably selectively locks during a desired phase in a gait cycle of the limb and minimizes friction against a rotor of the actuator. A processing module may control movement of the actuator based on data obtained from a sensor module. For instance, sensing module data may include information relating to the gait of a user and may be used to adjust the foot unit to substantially mimic the movement of a natural, healthy ankle. The system may further accommodate, for example, level ground walking, traveling up/down stairs, traveling up/down sloped surfaces, and various other user movements. In addition, the processing module may receive user input or display output signals through an external interface. For example, the processing module may receive a heel height input from the user.