The demand for advanced wearable robotic systems for the lower-extremity has grown in many fields, with clinical, industrial, and military applications. In fact, over the past decade, we have witnessed an increasing attention and recent progress in wearable robotic systems including lower-extremity exoskeletons, active prosthetic devices, and soft exo-suits. As the wearable robotic systems operate in close contact with the human body, it is crucial to understand interaction mechanics during dynamic tasks, such as locomotion. Despite the growing consensus on the importance of understanding interaction mechanics, its translation to the development and control of wearable robotic systems has not been fully achieved. In this workshop, we will discuss the current state-of-the-art in this field, including but not limited to system identification of human joint/limb dynamics, novel sensors and actuators for wearable robots, and human-in-the-loop control of wearable systems. In addition, we will discuss the technical limitations and future challenges we must overcome to advance research and development of wearable robotic systems for lower-extremity.