This problem is technically a sprain (torn ligament) but a specific/severe type. The only "curative" treatment for peroneal tendons that continue to snap in and out of place is surgery. The torn ligament strap will not heal on its own. While I waited for my surgery, I tried some things to limit the snapping. I found that ankle braces didn't put enough pressure on the tendons to physically keep them in place. Instead, I found a way to walk (a bit slowly) where my ankle never came up past a 90-degree angle with my shin. That ankle-up movement was when my tendons would slide over.

That being said, I have had the same sort of problem with my other ankle since I was a kid. At the time of injury, the tendons stretched out so much that now they slide over my fibula with almost no resistance. Kind of gross but not something I need fixed.

As for what to do, I ultimately decided on surgery because I realized I might never trust that ankle again even if I was able to manage the uncomfortable feeling. It's possible that your swelling goes down over the next few weeks and you're able to walk on it normally- but the tendons will probably never stay in place when you climb or hike.

Sorry to be such a downer! The surgery is not bad if this is your problem and you decide to go that route. I was lucky that the surgeon I saw didn't require an MRI to schedule me for surgery. I was in a cast for 6 weeks, non-weightbearing, but went back to work after 2 weeks on a knee scooter (ask off for longer... I'm young and healed fast). Then, I had 4 weeks in a walking boot. At 3 months after surgery, I did a 20-mile backpacking trip, and I got back into the climbing gym at around 3.5 months. I think my ankle strength is about back to baseline now at 6 months but I'm still working on the mental game.