Medically reviewed by Dr. Tom Biernacki, DPM
Board-certified podiatric surgeon | Balance Foot & Ankle, Howell & Bloomfield Hills, MI
Last reviewed: May 2026
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| Feature | Iselin Disease | 5th Metatarsal Avulsion Fracture | Jones Fracture | Os Vesalianum (Accessory Ossicle) |
|---|---|---|---|---|
| Definition | Apophysitis (traction on unfused growth plate) of 5th metatarsal base | Acute fracture at 5th MT base from peroneus brevis pull | Stress fracture at metaphyseal-diaphyseal junction (zone 2) | Congenital unfused ossification center at 5th MT base |
| Age group | 8–13 years (girls) / 10–15 years (boys); active apophysis | Any age; adolescents and adults | Young athletes 15–35 | Any age; congenital variant |
| Onset | Gradual; activity-related; insidious | Acute; inversion injury; sudden pop | Gradual or acute; chronic repetitive stress | Usually asymptomatic; pain only with irritation |
| X-ray margins | Irregular, slightly sclerotic apophysis; PARALLEL to metatarsal shaft | TRANSVERSE fracture line through apophysis | Fracture line PERPENDICULAR to shaft at meta-diaphyseal junction | Smooth, well-corticated margins; no fracture line |
| Bilateral | Common (bilateral apophysis is normal) | Unilateral | Unilateral | Often bilateral |
| Treatment | Activity modification, walking boot 2–4 weeks, heel wedge; resolves with skeletal maturity | Hard-soled shoe or boot 4–6 weeks; surgery if displaced >2 mm | NWB cast 6–8 weeks; surgery preferred in athletes (intramedullary screw) | Supportive care; rarely symptomatic enough to require excision |
| Prognosis | Excellent — always resolves when growth plate fuses (~age 12–16) | Good — most heal in 4–8 weeks | High nonunion risk (15–25%) without surgery | Excellent if asymptomatic |
| Age Range | Apophysis Status | Typical Activity Level | Management |
|---|---|---|---|
| Under 8 years | Not yet ossified; apophysis not visible on X-ray | Recreational | Iselin disease uncommon; consider other diagnoses |
| 8–10 years (girls) / 10–12 years (boys) | Apophysis appears; growth plate open and vulnerable | Often highest sports participation onset | Activity modification, heel wedge, avoid barefoot; boot if needed |
| 11–13 years (girls) / 13–15 years (boys) | Apophysis partially fused; peak pain period often during growth spurts | Competitive sports | Boot 3–6 weeks; physical therapy; lateral offloading orthotic |
| 14–16 years (girls) / 15–17 years (boys) | Apophysis fusing; pain typically resolving | Variable | Conservative; return to sport as tolerated |
| Skeletal maturity | Growth plate fully fused; Iselin disease no longer possible | Adult sports | No Iselin disease at this age — re-evaluate diagnosis |
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Medically Reviewed | Dr. Tom Biernacki, DPM | Board-Certified Podiatric Surgeon | Balance Foot & Ankle, Michigan
What Is Iselin Disease?
Iselin disease — named for surgeon H. Iselin, who first described it in 1912 — is traction apophysitis of the fifth metatarsal base, analogous to Sever’s disease at the calcaneus. During childhood and early adolescence, the secondary ossification center (apophysis) of the fifth metatarsal styloid process is a cartilaginous, relatively weak interface between the bone and the peroneus brevis tendon insertion. Repetitive eversion forces from the peroneus brevis — which fires with every step to stabilize the ankle against inversion — create cumulative traction stress at this growth plate, causing inflammation, microavulsion, and pain.
The condition primarily affects active children between ages 8 and 13, during the period of peak growth plate vulnerability. Athletes in soccer, basketball, gymnastics, and track are most commonly affected — sports with frequent lateral cutting, jumping, and ankle eversion loading. Like other pediatric apophysitides (Sever’s, Osgood-Schlatter at the knee, Sinding-Larsen-Johansson at the patellar tendon), Iselin disease is self-limiting and resolves when the apophysis fuses to the metatarsal shaft at skeletal maturity.
How Iselin Disease Presents
Affected children complain of lateral foot pain at the base of the fifth metatarsal — the bony prominence at the outer mid-foot. Pain is reproduced by direct palpation over the styloid process and worsens with running, cutting, and jumping. Some children present with localized soft-tissue swelling. The pain often begins insidiously during or after sports practice, progresses over weeks, and may become severe enough to produce an antalgic gait or force the child to sit out of athletic participation.
A classic distinguishing feature: Iselin disease pain is specifically at the styloid process (the prominent bump at the fifth metatarsal base), not at the diaphyseal shaft where Jones fractures occur, and not at the metaphyseal flare where tuberosity avulsion fractures happen. This anatomical localization is the most important clinical differentiator.
Diagnosis: Distinguishing Iselin from Fifth Metatarsal Fractures
The crucial differential diagnosis is between Iselin disease (a traction apophysitis) and two fractures that occur at the fifth metatarsal base in different locations and with different management implications:
The tuberosity avulsion fracture (pseudo-Jones fracture) occurs at the very tip of the styloid process in acute inversion injuries, where the peroneus brevis pulls off a fragment of bone. It is a traumatic injury in adolescents and adults (rare in children under 10), heals well with protected weight-bearing, and shows an irregular, non-corticated fracture line on X-ray.
The Jones fracture occurs 1.5–2 cm distal to the styloid, in the vascular watershed of the diaphyseal-metaphyseal junction. Jones fractures are notorious for non-union and often require surgical fixation — particularly in athletes. They are associated with cavovarus foot alignment and typically occur from acute inversion or repetitive stress rather than traction apophysitis.
Iselin disease on X-ray shows a secondary ossification center at the styloid — a smooth, rounded, well-corticated apophyseal fragment that is a normal developmental structure, not a fracture. The key is that it appears in the correct age range with the characteristic clinical presentation. When the X-ray and clinical picture are inconsistent (traumatic mechanism, older age, disrupted cortex), MRI resolves ambiguity.
Treatment: Activity Modification and Immobilization
Iselin disease is managed conservatively — surgery is never required for primary apophysitis, and the condition self-limits with skeletal maturity. Management is stratified by severity:
Mild cases: Relative activity modification (reducing sports to pain-free levels), lateral heel wedge insole to reduce peroneus brevis tension, and calf and peroneal stretching. Children can typically continue modified athletic participation.
Moderate cases: Transition to low-impact activity (swimming, cycling) for 3–6 weeks; supportive athletic footwear with lateral heel wedge; consideration of a lateral pad to protect the styloid from direct contact pressure in cleated sports shoes.
Severe cases with significant limp or inability to bear weight: Short-leg walking boot for 4–6 weeks to off-load the apophysis completely, followed by gradual return to activity as symptoms resolve. Return to sports is guided by symptom resolution, not by a fixed timeline.
Physical therapy focusing on calf and peroneal flexibility, intrinsic foot strengthening, and proprioceptive training addresses the underlying biomechanical contributors and reduces recurrence risk during the active apophysitis phase. NSAIDs and ice provide symptomatic relief during acute flares.
Prognosis: Complete Resolution Expected
Iselin disease has an excellent prognosis. The apophysis fuses to the metatarsal shaft between ages 12–16 (earlier in girls than boys), permanently eliminating the vulnerable growth plate. After fusion, recurrence is impossible and the fifth metatarsal functions normally. Long-term studies confirm no increased risk of lateral foot pain, peroneus brevis tendon problems, or foot arthritis in adults who had Iselin disease as children.
Parents should understand that Iselin disease is analogous to “growing pains” in a specific structural sense — it is a consequence of the growing skeleton’s vulnerability during peak athletic participation, not a sign of a serious injury or lasting damage.
Frequently Asked Questions
Is Iselin disease the same as a Jones fracture?
No — they are completely different pathologies. Iselin disease is apophysitis (traction inflammation) at the fifth metatarsal styloid, occurring in children ages 8–13 from peroneus brevis traction. Jones fracture is a stress fracture 1.5–2 cm distal to the styloid in the avascular diaphyseal-metaphyseal junction, occurring in adolescents and adults with high non-union risk. The distinction is critical because Jones fractures in athletes are frequently treated surgically, while Iselin disease never requires surgery. Both are on the outer foot, but at distinctly different anatomical locations.
How long does Iselin disease last?
The symptomatic phase typically lasts 4–12 weeks with appropriate management. Some children have recurrent flares during growth spurts until skeletal maturity (ages 12–16). Complete and permanent resolution occurs when the apophysis fuses to the metatarsal shaft. Between episodes, children can often maintain athletic participation with activity modification and supportive footwear.
Can my child play soccer with Iselin disease?
Modified participation is often possible. Children who can run and cut without a limp may continue with softer cleated footwear, lateral heel wedging, and styloid padding. Children who limp during play or experience pain that worsens through the practice should rest until symptoms subside. The goal is maintaining as much athletic participation as safely possible while preventing the pain from becoming severe enough to require complete sports withdrawal. Dr. Biernacki tailors sport-specific return-to-play recommendations for each child.
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Dr. Tom says: “My daughter’s soccer coach noticed her limping and we saw Dr. Biernacki — diagnosed Iselin disease and recommended these heel cups. She was back to full practice within three weeks and the lateral foot pain didn’t return.”
Active children ages 8–13 with Iselin disease lateral foot pain during sports
Adolescents or adults with fifth metatarsal fractures requiring fracture boot or surgical consultation
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✅ Pros / Benefits
- Self-limiting condition — complete resolution expected at skeletal maturity
- Conservative management only — surgery never required for primary Iselin apophysitis
- X-ray reliably distinguishes apophysitis from Jones fracture and avulsion fracture
- Most children maintain modified athletic participation throughout treatment
❌ Cons / Risks
- Condition may recur during growth spurts until apophyseal fusion
- Lateral cleated footwear in sports like soccer limits modification options
- Diagnosis occasionally delayed when confused with lateral ankle sprain
- Severe cases require walking boot — 4–6 week sports hiatus
Dr. Tom Biernacki’s Recommendation
Iselin disease is the foot’s version of Sever’s disease — same mechanism, same age group, same excellent prognosis, just at a different growth plate. Every parent who brings in a limping soccer player with outer foot pain needs to hear three things: this is not a fracture, this will heal completely, and we can usually keep your child playing with the right modifications. The Jones fracture differentiation is critical — those two conditions look similar on the history but have completely different treatment implications. Weight-bearing X-ray answers the question immediately in experienced hands.
— Dr. Tom Biernacki, DPM | Board-Certified Podiatric Surgeon | Balance Foot & Ankle
Frequently Asked Questions
What is the apophysis of the fifth metatarsal?
The apophysis is a secondary ossification center — a separate growth plate — at the tuberosity (styloid process) of the fifth metatarsal where the peroneus brevis tendon inserts. It appears on X-rays as a separate small bone adjacent to the metatarsal base, typically between ages 8–12. It is distinct from the primary ossification center and will eventually fuse to the metatarsal shaft. During the period before fusion, it is vulnerable to traction stress from the peroneus brevis — which is the pathological mechanism of Iselin disease.
Should Iselin disease be treated with a cast?
Casting is rarely necessary. Most cases respond to activity modification, heel wedging, and supportive footwear. A removable walking boot is preferred over casting for severe cases because it allows daily skin inspection, facilitates easier hygiene, and permits progressive removal as symptoms improve. True immobilization casting is reserved for children with extremely severe pain or a concurrent stress response in the apophysis identified on MRI.
Is Iselin disease related to flat feet?
Flat feet increase subtalar pronation, which elevates the peroneus brevis activation demand to maintain lateral ankle stability — potentially increasing traction at the fifth metatarsal apophysis and predisposing to Iselin disease. Children with flexible flatfoot who develop Iselin disease benefit from orthotic arch support that reduces pronation and secondarily decreases peroneal loading. Dr. Biernacki evaluates foot alignment at every Iselin disease appointment and addresses flatfoot as a contributing factor when present.
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Frequently Asked Questions
What causes this condition?
Causes include mechanical stress, biomechanical imbalance, age-related changes, and sometimes systemic disease. Our clinical exam plus imaging identifies the specific driver.
Can it go away on its own?
Mild cases sometimes resolve with rest and supportive footwear. Persistent symptoms past 4-6 weeks rarely resolve without active treatment.
Is surgery required?
Most patients resolve with non-surgical care. Surgery is reserved for refractory cases or structural deformity.
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Dr. Tom Biernacki, DPM is a board-certified foot & ankle surgeon (ABFAS & ABPM) at Balance Foot & Ankle Specialists in Southeast Michigan. With over a decade of clinical experience, he specializes in heel pain, bunions, diabetic foot care, sports injuries, and minimally invasive surgery. Dr. Biernacki is a member of the APMA and ACFAS, and his patient education content on MichiganFootDoctors.com and YouTube has made him one of the most-followed foot & ankle educators on YouTube.