This paper presents a linkage system designed to guide a natural ankle trajectory with the corresponding foot orientation. A six-bar linkage was designed to coordinate the joint angles of an RR chain (R denotes a revolute or hinged joint) that models the leg to achieve the desired ankle trajectory. The design is shown to be adjustable to meet a range of trajectories obtained in an individual's normal gait. Control of the foot position is obtained using a cam-driven parallel chain that has the same input as the six-bar linkage. The design of the linkage was carried out using linkage synthesis theory and optimization methods. The result is a one degree-of-freedom system that guides a natural walking movement of the leg and foot. A solid model of the complete device is presented. The results of this research provide a procedure that focuses on the kinematics and mechanical design of a device named the UCI gait mechanism.