A mobility or walking aid (WA) comprising an exoskeleton, a control system for controlling movement of the exoskeleton, and a power source for providing power to the exoskeleton and the associated control system. The WA system may be configured as a fully supportive system to assist a paraplegic user for example, or as a partially or fully supportive system to assist in the rehabilitation of a user with limited mobility. When a mobility impaired user is secured to the WA, the user is caused to move their joints and muscles through motions of walking, thereby assisting in the prevention of deterioration of a user's physiology. The WA is provided with various user customisable features and safety mechanisms including leg length adjustments, foot member adjustments, user size calibration and mechanical safety stop configuration.