Iselin disease is a problem with the growth plate at the base of the fifth metatarsal where the peroneal brevis tendon attaches on the outside of the foot, most commonly around the age of 13.
Typically there is an insidious onset of pain at the base of the fifth metatarsal which get worse with exercise. Some have swelling and some walk with a limp. There is tenderness in the area and pain on resisted inversion.
All cases will resolve spontaneously as the growth plate fuses to the rest of the bone as part of normal development. It is, however, painful and does need to be treated and you can not wait for it to get better eventually. The first approach to manage Iselin disease is to reduce activity to a level that is tolerable. In some cases that does need to be no exercise or sport for a period of time. There may need to be the short term use of strapping and foot orthotics to help or even a moon boot. Once the symptoms start to settle it is then important to put in place a return to sports activity plan with a gradual increase in exercise.