- [Home](https://ortopediaevolutiva.com/en) - [Conditions](https://ortopediaevolutiva.com/en/conditions) - Iselin's Disease: Outer Foot Pain in Young Athletes Trauma & Sports # Iselin's Disease: Outer Foot Pain in Young Athletes Pain on the outer edge of the foot after sports: Iselin's disease is often mistaken for a sprain. Updated: March 2026 · Medically reviewed by Dr. Daniele Priano ## Quick Answers How is it distinguished from a fracture? + History, examination and image interpretation are needed. Normal apophyseal orientation helps, but smooth versus irregular margins are not enough: apophysitis may fragment and stress fractures may start without acute trauma. Further tests depend on clinical suspicion. Why is it confused with a sprain? + Lateral foot pain may initially be attributed to a sprain. Persistent pain requires reassessment of its precise site and history: Iselin apophysitis is one possibility, alongside fractures, stress injuries and other causes. Lack of improvement does not by itself establish a specific diagnosis. [See all 4 questions →](https://ortopediaevolutiva.com/en/conditions/iselins-disease#faqs) Here's a situation I see often in clinic: an athletic child complaining of pain along the outer edge of the foot, parents thinking it's an ankle sprain that "never heals," and maybe they've already been to the emergency room where they were told there's no fracture. Yet the pain persists. In these cases, the answer is often **Iselin's disease**. It's an apophysitis of the 5th metatarsal base — that bony point you can feel on the outer edge of the foot — where the peroneus brevis tendon inserts. In children aged **9 to 14**, the growth plate at this site is still open and vulnerable to overload. The main challenge with Iselin's disease is diagnostic: it can be confused with an ankle sprain (same painful area) or a 5th metatarsal base fracture. The difference is both clinical — gradual, sport-related onset is typical of apophysitis — and radiographic: the normal apophysis runs along the metatarsal, whereas many avulsion fractures have a different orientation. Smooth margins or absence of trauma do not exclude a fracture, including stress injury; a clinician must interpret the images. When pain instead appears suddenly after an inversion injury, a different picture must be considered: see [fifth metatarsal base fracture in children](https://ortopediaevolutiva.com/en/conditions/fifth-metatarsal-base-fracture). In the large majority of cases it **settles with skeletal maturity** and treatment is conservative: load modification and, when indicated, comfort measures or selected exercises. Stretching that provokes pain at the metatarsal base is not forced. A cast is rarely needed, only when pain is significant even during daily activities. ## Assessment and treatment ### When to seek evaluation - Pain on the outer edge of the foot during sports - Pain at the base of the 5th metatarsal - Pain mistaken for a 'sprain that won't heal' - Limping after running or on uneven terrain - Tenderness over the 5th metatarsal base ### What is evaluated - Palpation of the 5th metatarsal base - Resisted foot eversion test - Differential diagnosis with avulsion fracture and Jones fracture - Foot X-ray (to distinguish normal apophysis from fracture) - Ankle stability assessment ### Treatment options - Sports load reduction - Insoles with lateral arch support - Peroneal muscle stretching - Supportive shoes with stable sole - Ice after activity - Gradual return to sports ## Frequently Asked Questions How is it distinguished from a fracture? ▼ History, examination and image interpretation are needed. Normal apophyseal orientation helps, but smooth versus irregular margins are not enough: apophysitis may fragment and stress fractures may start without acute trauma. Further tests depend on clinical suspicion. Why is it confused with a sprain? ▼ Lateral foot pain may initially be attributed to a sprain. Persistent pain requires reassessment of its precise site and history: Iselin apophysitis is one possibility, alongside fractures, stress injuries and other causes. Lack of improvement does not by itself establish a specific diagnosis. Does it heal completely? ▼ The prognosis is generally favourable: the apophysis fuses with the 5th metatarsal base during skeletal maturity and symptoms tend to resolve. Long-term consequences are uncommon, but the child should be followed clinically until the pain settles. Is a cast needed? ▼ Usually not. Loading is modified and comfort measures selected as appropriate; insoles and stretching are not compulsory for everyone. The clinician may prescribe immobilisation when pain and limitation warrant it. ## Other Juvenile Osteochondroses Osteochondroses are a family of growth-related conditions. Learn about the others: [🦵 Osgood-Schlatter (Knee)](https://ortopediaevolutiva.com/en/conditions/osgood-schlatter-disease)[🦶 Sever (Heel)](https://ortopediaevolutiva.com/en/conditions/severs-disease)[🦵 Sinding-Larsen (Kneecap)](https://ortopediaevolutiva.com/en/conditions/sinding-larsen-johansson-syndrome)[🦶 Köhler (Foot)](https://ortopediaevolutiva.com/en/conditions/kohlers-disease)[🦶 Freiberg (Forefoot)](https://ortopediaevolutiva.com/en/conditions/freibergs-disease)[💪 Panner (Elbow)](https://ortopediaevolutiva.com/en/conditions/panners-disease) [Complete guide to juvenile osteochondroses →](https://ortopediaevolutiva.com/en/conditions/juvenile-osteochondrosis) **Important Notice:** The information on this page is for educational and informational purposes only and does not constitute medical advice. Each clinical case is unique: the appropriate treatment is determined during the specialist consultation, based on a thorough clinical examination and, where necessary, diagnostic imaging. For any doubts or concerns, please consult a specialist. ## Complete pathway on osteochondroses and apophysitis in sport This page is part of the pathway on osteochondroses and apophysitis in growing children. - [6 Iselin’s disease (fifth metatarsal base) · you are here Apophysitis on the outer border of the foot between 9 and 14 years, often mistaken for a sprain that "won't heal": telling it apart from an avulsion fracture is the key point.](https://ortopediaevolutiva.com/en/conditions/iselins-disease) [Exercise sheet: Iselin’s disease](https://ortopediaevolutiva.com/en/parents-kids/exercises/foot-ankle/iselin-exercises) - [3 Sever’s disease (calcaneal apophysitis)](https://ortopediaevolutiva.com/en/conditions/severs-disease) - [1 Osteochondroses and apophysitis: overview](https://ortopediaevolutiva.com/en/conditions/juvenile-osteochondrosis) Adjacent clinical pictures: [Cavus foot](https://ortopediaevolutiva.com/en/conditions/cavus-foot) ## Learn more - [Home exercises →](https://ortopediaevolutiva.com/en/parents-kids/exercises/foot-ankle/iselin-exercises) [All conditions](https://ortopediaevolutiva.com/en/conditions)[Medical glossary](https://ortopediaevolutiva.com/en/glossary) --- Canonical: https://ortopediaevolutiva.com/en/conditions/iselins-disease Le informazioni cliniche sono divulgative e non sostituiscono una valutazione medica diretta.