This study is looking at how well two pain medicines, **EXPAREL** and **bupivacaine**, help people who have had ankle surgery. *EXPAREL* is a new kind of medicine that lasts longer to reduce pain after surgery. *Bupivacaine* is a common pain medicine. The study wants to see which one works better and if *EXPAREL* helps people use fewer opioids, which are strong pain medicines that can have side effects. **Key Points:** - **Duration:** The study compares pain relief for up to 96 hours after surgery. - **Visits:** Participants will follow a study schedule and complete all assessments. - **Eligibility:** Participants need to be planning to have one ankle replaced and be in generally good health, with some specific conditions excluded. This study could help improve pain relief and recovery after ankle surgery while reducing the need for opioids. If you're eligible and participate, you'll be helping doctors find better ways to manage post-surgery pain. Please remember to speak to your doctor for more information and whether this study is right for you.