A prosthesis system can have an advantageous use over conventional prostheses in certain activities, including, but not limited to certain sports activities: The system includes, elastic member(s) that can store and release energy. The storing and releasing of energy in the elastic members happens during the movements made by the user and with the application of the user's own body weight while performing an activity. Implementations can also include a variety of routing configurations for the elastic member(s), as well as a variety of mounting points to integrate the elastic member(s) into the system, and/or a variety of adjustable anti-hyperextension members, and/or a variety of interchangeable shoes used for applicable activities.