Peroneal tendonitis is the inflammation of a tendon in your outer (lateral) ankle. The peroneal muscles run down the back of the lower leg, and the tendon runs behind the bump on your outer ankle (lateral malleolus). When the tendon is irritated, it can cause swelling on the outer ankle and ankle pain when walking or exercising. These stretches and exercises should help.
Since the peroneal muscles runs behind and to the outside of the leg, it’s important to stretch the calf area. You can do this with your legs out in front of you or standing up. You can even stretch your Achilles tendon and peroneal tendon on a step.
Strengthening the peroneal tendon and muscles are also important. Since it helps the ankle go into eversion, you can easily exercise them with a resistive band.
Another great way to exercise the whole ankle area is with standing heel/toe raises as well as a balance series.
Finally, a side step up, because of the side to side movement helps strengthen the whole ankle area.