In athletes if there is pain on the lateral side of the ankle joint and there is no sign of trauma, then the most likely issue is what is called peroneal tendonitis. The peroneal muscle group are on the lateral side of the lower leg and there tendons move around the outside of the ankle joint to then pass to the outside and then the underside of the foot. The major function of the peroneal muscles will be to stabilize and support the foot.
If a tendonitis develops in the tendons of the peroneal muscles in athletes, then the reason is usually overuse. That is running too much too early and the peroneal tendons are not given an opportunity to adapt to the increasing loads which are placed on them coming from that too fast increase in the miles as well as speeds being run. It is vital that after tough long runs that the body is provided ample relaxation prior to the next stress are applied. When a stress is put on too soon prior to the tissues to have had time to recuperate, then there is an increased possibility for an overuse injury.
The pain sensation of peroneal tendonitis in most cases only starts of like a minor ache, either just above or below the ankle bone on the outside of the ankle. To start with there isn't any puffiness, but that will tend to develop later as the pain increases if the problem is not addressed.
To take care of peroneal tendonitis, the athlete needs to lower the running to tolerable distances to enable the peroneal tendons to heal. Podiatric doctors frequently use a lateral wedge to help remedy peroneal tendonitis for the short term because this decreases the activity with the peroneal muscles, so there will be less load on the peroneal tendons. This is placed under the heel in the running shoes. Right after the pain in the peroneal tendon begins to settle down, then a steady and slow increase is required in the mileage run to enable the tendon to adapt to those loads are needed. A strengthening plan can be beneficial.