Employing six-bar linkages for knee orthoses is an advantageous choice in many ways. In relation to four-bar linkages the six-bar linkage tracks more accurately the natural ankle trajectory and provides more flexibility in the design for stability. Additionally, the 1-DOF mobility of linkages alongside the available moment leverage offers advantages in cost-effectiveness over open-kinematic-chain designs. This work presents the analysis as well as the design and optimization considerations of a knee orthosis that is based on a Watt’s six-bar linkage. The main aim is to lay the foundations for analytical design and development of a knee orthosis that is cost-effective, self-cancelling and optimized for passive-active energy exchange as well as energy harvesting and return.