Iselin’s disease is a traction apophysitis of the base of the fifth metatarsal, producing lateral foot pain in skeletally immature, typically athletic children and adolescents. It is an overuse injury of the apophyseal growth plate at the styloid process where peroneus brevis inserts, and is usually self‑limiting with conservative management.
Definition and epidemiology
Iselin’s disease, also called apophysitis of the fifth metatarsal base or Iselin’s osteochondrosis, is an osteochondrosis of the secondary ossification centre at the tuberosity of the fifth metatarsal. The apophysis lies within the insertion of the peroneus brevis tendon, and radiographically appears around age 10 in girls and 12 in boys, fusing by roughly 11 and 14 years respectively. Because it is linked to growth plate physiology and traction, the condition is almost exclusively seen in active children aged about 9–14 years engaged in sports involving running, cutting, and jumping such as football, basketball, and ballet. It is considered relatively uncommon but probably under‑recognised in primary care and general musculoskeletal practice.
Pathophysiology and aetiology
The underlying pathology is traction‑induced inflammation and microtrauma of the cartilaginous apophysis at the base of the fifth metatarsal. Repetitive loading of the peroneus brevis tendon during activities that involve rapid inversion–eversion, push‑off, and lateral cutting produces shear forces across the open growth plate. Over time, this mechanical stress leads to oedema and fragmentation within the apophysis, visible on imaging as irregularity and sclerosis. Contributory biomechanical factors include overuse from high training volumes, muscular tightness or weakness (for example tight gastrocnemius–soleus complex or weak lateral stabilisers), and footwear that fails to provide adequate lateral support and cushioning. Because the growth plate cartilage is softer and less resilient than mature bone, it is more susceptible to this repetitive traction until physeal closure occurs.
Clinical presentation
Children typically report insidious onset pain along the outer border of the foot centred on the base of the fifth metatarsal, aggravated by activity and relieved by rest. Symptoms often flare with running, jumping, tip‑toeing, or sports training sessions and settle between activities, at least in early stages. Parents and clinicians may observe a limp or a tendency to walk on the medial border of the foot to unload the symptomatic lateral apophysis. On examination, there is focal tenderness at the widest part of the lateral midfoot over the styloid process, frequently accompanied by localised swelling, erythema, or a palpable “lump” at the fifth metatarsal base. Pain is reproduced with direct palpation and often with resisted eversion or passive inversion that tensions peroneus brevis; in more irritable cases, range of motion of the foot and ankle may be limited by discomfort and the child may struggle to participate fully in sport.
Diagnosis and differential diagnosis
Diagnosis is primarily clinical, based on the characteristic history of activity‑related lateral foot pain in a skeletally immature athlete and focal tenderness at the fifth metatarsal base. Plain radiographs are not always required but can assist in excluding acute fractures and in demonstrating typical apophyseal changes when indicated. Radiographic features include a longitudinally oriented, irregular apophysis with sclerosis and possible fragmentation that remains in continuity with the metatarsal base, distinguishing it from a transverse avulsion (pseudo‑Jones) fracture or more proximal Jones fracture. Other important differentials are os vesalianum (an accessory ossicle lateral to the fifth metatarsal), stress fracture, peroneal insertional tendinopathy, and less commonly infection or neoplasm in atypical presentations. In equivocal or refractory cases, MRI can demonstrate bone marrow oedema within the apophysis and adjacent metatarsal base and associated soft‑tissue oedema, confirming the diagnosis and excluding other pathology.
Management
Management of Iselin’s disease is almost always conservative and directed at load modification and symptom control. Initial treatment emphasises relative rest from provoking activities, particularly high‑impact running and jumping, along with ice and simple analgesia or non‑steroidal anti‑inflammatory medication as required. Short‑term immobilisation in a walking boot or stiff‑soled shoe may be useful in more severe cases to reduce traction forces and allow the inflamed apophysis to settle. Addressing underlying biomechanical contributors is equally important and may include calf and peroneal stretching, strengthening of intrinsic and peroneal musculature, and correction of any foot posture issues with supportive footwear or orthoses to offload the lateral border. A graded return‑to‑sport programme is then implemented, increasing activity volume and intensity only as symptoms permit and ensuring the child can run, cut, and jump pain‑free before full competition. Surgery is not indicated; contemporary paediatric orthopaedic and sports medicine sources emphasise that operative treatment is unnecessary and that outcomes with conservative care are excellent.
Prognosis and clinical significance
Prognosis for Iselin’s disease is favourable, with symptoms generally resolving as the apophysis matures and fuses once mechanical loading is optimally managed. Most children return to full activity without long‑term sequelae when diagnosis is timely and activity modification implemented early. Persistent pain is usually related to continued overuse, poor adherence to rest or rehabilitation, or misdiagnosis of a true fracture or other pathology. The main clinical importance of recognising Iselin’s disease lies in distinguishing it from avulsion or Jones fractures of the fifth metatarsal, which require different management and have different risks, and in avoiding unnecessary investigations or immobilisation in a condition that is self‑limiting when managed appropriately. For clinicians in paediatric sports and foot health, awareness of this entity and its biomechanical underpinnings supports targeted load management, education, and rehabilitation strategies that allow young athletes to maintain participation while protecting the vulnerable apophysis.


