In athletes if there is discomfort on the outside of the ankle joint and there is no history of trauma, then the most likely reason is what is called peroneal tendonitis. The peroneal muscles are on the outside of the lower leg and there tendons pass around the lateral side of the ankle joint to then go to the outside and the bottom of the feet. The fundamental purpose of the peroneal muscles will be to balance and support the arch.
If a tendinopathy occurs in the tendons of the peroneal muscles in runners, then the reason is usually overuse. This is doing too much too early and the peroneal tendons are not provided an opportunity to adapt to the increasing loads which are placed on them coming from that too rapid increase in the distances and also speeds being run. It is important that after hard longer runs that the body will be provided appropriate recuperation ahead of the next load is applied. When a load is applied too quickly before the tendons to have had time to restore, then there is an increased possibility for an injury.
The pain sensation of peroneal tendonitis usually only starts of as a modest ache, either just above or below the ankle bone on the lateral side of the ankle. At first there is no puffiness, however that will normally come about later since the pain increases when the issue is not addressed.
To cope with peroneal tendonitis, the athlete needs to cut back the running to tolerable amounts to permit the peroneal tendons to heal. Foot doctors often make use of a lateral wedge to take care of peroneal tendonitis for the short term because this lessens the activity with the peroneal muscles, so there is reduced load on the peroneal tendons. The wedge goes under the heel in the running footwear. When the pain in the tendons starts to calm down, then a steady and slow increase is needed in the distances run to allow the tendon to adjust to the stresses are essential. A strengthening plan can also be worthwhile.