This paper describes the design, implementation, and preliminary validation of a controller for a powered lower-limb exoskeleton that reshapes a user's leg movement during over-ground walking. The intended application of the controller is to facilitate gait training for individuals suffering from post-stroke hemiparesis. The controller mimics a kinematic constraint between the knee and hip joints during the swing phase of gait, such that movement is not dependent on time (i.e., step time is determined entirely by the user). The controller additionally incorporates real-time path planning adjustment that allows step length to be adjusted by the user. As such, the controller provides movement coordination, but still enables a user to retain the step-to-step variability required to maintain balance during walking. As a preliminary assessment of efficacy, the controller was implemented on a lower limb exoskeleton and tested on a healthy subject, who walked at varying speeds without the use of a stability aid, with and without the proposed controller. The data indicates that the exoskeleton with controller provided the intended extent of movement coordination, while still allowing the subject to maintain walking balance.