An exoskeleton device that includes an artificial joint and a frame member extending from the artificial joint. The frame member is configured for extension over a limb of a user. The exoskeleton device also includes a self-aligning mechanism connected to the frame member. The self-aligning mechanism includes three passive degrees of freedom (pDOF) provided in a prismatic-revolute-revolute (PRR) configuration. The self-aligning mechanism also includes a limb attachment member configured for mechanically coupling to a portion of the limb of the user.