A lower extremity exoskeleton is device which can enhance the human strength and speed while walking and running. It mimics the human gait motion and enhance the endurance of human with help of actuators to carry heavy loads. It can help to carry heavy loads in rough terrain where a wheeled vehicle can't reach. The most prominent option for elderly people and people with walking disabilities such as paraplegia is to use a wheelchair, which is not convenient in every environment. A lower extremity exoskeleton with the particular purpose of either power augmentation or gait assistance can solve this problem. This paper discusses an overview on the historical developments in the field of exoskeleton type system along with the biomechanical considerations and the human gait cycle for the development of a lower extremity exoskeleton and analyses various parameters needed for the design of a lower limb exoskeleton system. The kinematic analysis of human lower limb is studied using Denavit-Hartenberg (DH) parameters. Furthermore, a comparison of the degrees of freedom and their ranges along with the actuators used in various exoskeleton developed is discussed. © 2023