Iselin disease is a uncommon cause of pain on the outer side of the feet in youths and teenagers. This condition is an osteochondrosis or traction apophysitis in the base of the 5th metatarsal metatarsal. The peroneal brevis tendon attaches on the site and puts the bone with a lot of strain. https://podiatrynewyorkcity.com/iselins-disease-of-the-fifth-metatarsal/