Passive energy storage and return has long been recognized as one of the central mechanisms for minimizing the energy cost needed for terrestrial locomotion. Although the hip capsule resides the strongest ligaments in the body, its potential role in energy-efficient walking remains unexplored. Increasing our understanding of soft-tissue balancing following THA could help prevent instability and improve early and long-term hip function. Clearly, our understanding of the hip capsule and its role in human mechanics remains largely incomplete. This research proposal aims to address this important gap by investigating the active and passive role of the hip capsule in hip functioning by examining the impact of implant design, anatomical variance and surgical handling on the properties of the hip capsule. This research will inform the development of improved surgical techniques and implant designs that can optimize patient outcomes and enhance long-term performance following hip arthroplasty.