Iselin's Disease: Outer Foot Pain in Active Kids

Quick answer

Iselin’s disease is inflammation of a growth plate (called an apophysis) at the base of the 5th metatarsal in children, usually between ages 8 and 13. The peroneus brevis tendon attaches to this growth plate, and repetitive pull from running, jumping, and cutting sports irritates the still-developing cartilage. It is the lateral-foot counterpart of Sever’s disease (heel apophysitis) and behaves similarly: painful but self-limited, never permanent, and treated with activity modification rather than rest or casting.

What it is

In growing children, the bones of the foot have soft cartilage growth zones (called apophyses or growth plates) where new bone is being laid down and where major tendons attach. The 5th metatarsal has its own small apophysis at the base, where the peroneus brevis tendon inserts.

This area is mechanically vulnerable in active kids:

• Repetitive pull from sports loads the immature cartilage
• Inflammation builds up faster than the growing tissue can adapt
• The result is pain, tenderness, and sometimes mild swelling at the base of the 5th metatarsal

It is not a fracture — though it is sometimes confused with one on X-rays, especially Jones fracture in older teens.

Who gets it

Iselin’s disease almost exclusively affects:

• Children and young teens between approximately ages 8 and 13 (girls slightly earlier than boys, matching skeletal maturity timing)
• Active kids in sports involving running, jumping, cutting, or repeated foot inversion: soccer, basketball, gymnastics, dance, lacrosse, football
• Recent growth spurts — fast linear growth tightens muscles and tendons relative to bone length, increasing apophyseal traction

Symptoms

• Pain on the outside of the foot, well-localized to the base of the 5th metatarsal
• Tenderness on direct pressure over the area
• Pain worse with activity (especially running, jumping, cutting), better with rest
• Mild swelling or a visible bump in some cases
• Limping during or after sport
• No history of acute injury in most cases (this is overuse, not a fall or twist)

Diagnosis

• History and exam are usually enough — age, activity level, location of tenderness, and pattern of symptoms
• X-rays are often ordered to rule out fracture, especially Jones fracture. The apophysis can sometimes look fragmented or widened on X-ray, which is normal at this age but can confuse less experienced readers.
• MRI is rarely needed but can show inflammation and edema at the apophysis if the diagnosis is unclear

Treatment

The principle: calm the inflammation, modify the load, let the growth plate keep maturing.

Activity modification (first-line)

• Stop the painful activity for 2 to 6 weeks (depending on severity)
• Continue cross-training (swimming, cycling, upper-body work) to maintain fitness without loading the foot
• Return to sport gradually as pain settles, not all at once

Symptom relief

• Ice the painful area for 15 to 20 minutes after activity or at the end of the day
• NSAIDs (ibuprofen) for short periods if pain is significant — discuss with the child’s pediatrician
• Stiff-soled shoe or walking boot for 1 to 2 weeks in moderate cases
• Padding (a small felt or gel pad over the area inside the shoe) to reduce direct pressure

Stretching and strengthening

• Calf and peroneal stretching once acute pain has subsided
• Foot intrinsic strengthening as part of return-to-sport
• A pediatric physical therapist or sports medicine clinician can guide age-appropriate exercises

What does NOT help (and may harm)

• Casting is rarely needed and can lead to deconditioning
• Cortisone injection is generally avoided in children with growth-plate conditions
• Pushing through significant pain — risks tipping into an actual apophyseal avulsion (where the growth plate pulls off the bone)

When to see a clinician

• Lateral foot pain in a child or young teen that lasts more than 1 to 2 weeks
• Pain that worsens with sport despite rest
• Visible swelling or a bump at the base of the 5th metatarsal
• Limping that does not resolve
• Any concern about a fracture (sudden injury, severe pain, inability to bear weight)

Bottom line

Iselin’s disease is a common, self-limited overuse condition of the growth plate at the base of the 5th metatarsal in active 8- to 13-year-olds. It is not a fracture and does not cause permanent damage. Most children improve within 4 to 8 weeks of activity modification, ice, and proper footwear. The growth plate eventually fuses naturally in mid-adolescence and the condition cannot recur after that point.