When a robot physically interacts with a human user, the requirements should be drastically changed, The most important requirement is the safety of the human user in the sense that robot should not harm the human in any situation. During the last few years, research has been focused on various aspects of safe physical human robot interaction. This paper provides a review of the work on safe physical interaction of robotic systems sharing their workspace with human users(especially elderly people). Three distinct areas of research are identified: interaction safety assessment, interaction safety through design, and interaction safety through planning and control. The paper then highlights the current challenges and available technologies and points out future research directions for realization of a safe and dependable robotic system for human users.