Iselin Disease: Apophysitis of the 5th Metatarsal Base in Young Athletes

Iselin disease is a traction apophysitis of the secondary ossification center at the base of the fifth metatarsal — the same bony prominence where the peroneus brevis tendon inserts. It is the foot equivalent of Osgood-Schlatter disease, occurring in active children and adolescents during the growth spurt when the apophysis is open and vulnerable to repetitive tensile stress from the peroneus brevis. The condition is frequently misdiagnosed as a Jones fracture or dancer’s fracture because the pain is at the lateral foot base, but the mechanism, age group, imaging findings, and treatment are entirely different. Correct diagnosis prevents unnecessary immobilization and guides appropriate return-to-sport planning.

Iselin Disease vs. 5th Metatarsal Fracture: Distinguishing Features

Feature	Iselin Disease (Apophysitis)	5th Metatarsal Base Fracture
Age group	8-14 years (girls 8-10, boys 10-14); coincides with growth spurt and apophysis ossification	Any age; acute fractures more common in adults; stress fractures in adolescent athletes
Onset	Insidious; weeks of progressive activity-related lateral foot pain; no specific trauma event	Acute traumatic event (inversion sprain for avulsion fracture); or stress fracture with gradually worsening pain
X-ray appearance	Apophysis appears as a secondary ossification center parallel to the metatarsal shaft — normal variant that can be mistaken for fracture; fragmentation of apophysis in severe cases	Fracture line perpendicular to metatarsal shaft (avulsion zone 1); transverse fracture at metadiaphyseal junction (Jones zone 2); diaphyseal stress fracture (zone 3)
Apophysis orientation	Longitudinal — parallel to 5th metatarsal shaft; key distinguishing feature from fracture	Fracture lines are transverse or oblique to the shaft, not parallel
MRI findings	Edema at apophyseal cartilage; peroneus brevis tendon intact; no fracture line in cortical bone	Cortical fracture line; periosteal reaction; bone marrow edema at fracture site
Treatment	Activity modification; relative rest from high-impact sport; stretching; orthotics for overpronation; spontaneous resolution with skeletal maturity	Zone 1 avulsion: CAM boot 4-6 weeks; Zone 2 Jones: non-weight-bearing cast or surgical fixation; Zone 3 stress: surgery usually required
Return to sport	4-8 weeks activity modification; resume when pain-free; recurrence common if returned too early	Zone 1: 6-8 weeks; Jones fracture: 12-20 weeks; stress fracture: variable, surgery shortens timeline

Iselin Disease: Clinical Features and Management by Severity

Severity	Symptoms	X-ray	Management	Return to Sport
Mild	Pain only after activity; no limp; no tenderness at rest; active child with heavy training load	Normal apophysis or minimal fragmentation	Reduce training volume by 50%; cross-train with swimming/cycling; calf stretching; lateral heel wedge if pronated	2-4 weeks with pain resolution
Moderate	Pain during and after activity; mild limp; point tenderness at 5th metatarsal base with palpation	Fragmentation or sclerosis of apophysis; normal metatarsal shaft	CAM boot or firm-soled shoe 2-4 weeks; complete rest from impact sports; physical therapy for calf flexibility	4-8 weeks after pain resolution with gradual return protocol
Severe	Pain with walking; significant limp; unable to participate in any sport; swelling at lateral foot base	Marked fragmentation; periapophyseal soft tissue swelling on MRI	Non-weight-bearing CAM boot 3-4 weeks; then walking boot 2-4 weeks; MRI to confirm no fracture or osteochondral lesion	8-12 weeks; orthopedic or podiatric co-management

At Balance Foot & Ankle in Howell and Bloomfield Township, lateral foot pain in active children and adolescents is evaluated with weight-bearing X-rays interpreted with knowledge of normal apophyseal variants — the longitudinal orientation of the 5th metatarsal apophysis is the key feature distinguishing Iselin disease from fracture, and most cases resolve with activity modification rather than immobilization. Call (810) 206-1402.

More questions patients ask

How is Iselin disease diagnosed?

Diagnosis is based on patient age (typically 8–14 years), lateral midfoot pain with activity, and X-ray appearance of an irregular or fragmented apophysis at the fifth metatarsal base. Comparison views of the opposite foot are helpful.

How is Iselin disease treated?

Treatment is conservative: activity restriction, a walking boot or short leg cast for 4–6 weeks, followed by gradual return to sport. Surgery is almost never needed. The condition resolves with skeletal maturity in most patients.

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