Sounds like Peroneal Tendon Subluxation. Which is the moving of your peroneal tendons over the lateral malleoues. I developed this after a bad ankle sprain playing soccer. I tried conserative treatment i was put in a splint for a month, followed by a walking boot and a month of PT. I can through my day fine but any high impact activity still causes it to sublux. So im getting ankle surgery on the 20th of august to correct the condition. Some people are more prone to developing this after a bad sprain if the fibular groove is too shallow such as mine. The surgey consist of deepening the groove and thightening the recticulum which can be torn during a sprain. Anyways i hope this helps. Goodluck.