Iselin disease is a benign and self-limiting condition, defined as apophysitis of base of 5th metatarsal.

It is due to repetitive traction of peroneus brevis tendon at the site of its attachment. Predisposing factors are jumping and running.

Apophysis of the fifth metatarsal base appears on plain radiographs at age 12 for boys and 10 for girls. Fusion of the apophysis to the metatarsal base usually occurs within the following 2–4 years.