Iselin's disease

What is Iselin's disease?

Iselin's disease is an overuse problem at a growth centre on the outer side of the foot, at the base of the fifth metatarsal (the long bone behind your little toe). The clinical name is traction apophysitis of the fifth metatarsal: irritation of a growth centre from repeated pulling¹. It affects growing children and teenagers, especially those who play regular sport¹².

The growth centre is a small fleck of bone on the outer side of the foot. It has been reported to appear at about 8–10 years of age in girls and 10–15 years in boys³.

Iselin's disease is described as rare, but it's probably more common than people realise⁴. It's rarely reported and probably often goes undiagnosed, sometimes because it's mistaken for a fracture¹.

What causes it, and who gets it?

The likely cause is repeated pulling on the growth centre by the peroneus brevis tendon (a tendon that runs along the outer side of the ankle and foot), before the growth centre has joined the bone⁵. It mainly affects children aged 8 to 13 and is reported as more common in boys⁵. Soccer, dance, basketball and running are linked with it⁵. Another report suggests suspecting it in active children aged 10–15 with outer foot pain⁶. These are general descriptions, not firm limits.

For young athletes in general, overuse growth-plate injuries have several causes. Muscle imbalances after fast growth spurts make injury more likely, and so do things that can be changed: flexibility, strength, how much they train and how they're coached⁷.

What does it feel like, and what else could it be?

Iselin's disease causes pain at the bony bump on the outer side of the foot, at the base of the fifth metatarsal. The pain gets worse with sport, isn't linked to a particular injury, and pressing on the spot brings it on⁵. The diagnosis usually rests on the history and an examination, and scans are not routinely required in the early stages⁵. An X-ray is sometimes added⁸. It may show the growth centre as stretched, uneven or in pieces⁵. Early or slight changes can be subtle on X-ray, and an MRI scan can be needed to show the problem when X-rays look normal⁶⁹.

Several problems at the same spot can look alike. They include an avulsion fracture (a small piece of the fifth metatarsal base pulled off), a Jones fracture, a stress fracture in the shaft of the bone, and os vesalianum (an extra small bone)¹⁰⁶. A fracture usually follows a clear, sudden injury, whereas Iselin's disease isn't tied to one particular injury⁵. A normal growth centre is also often mistaken for a fracture on X-ray³. Getting it right matters, because a delayed diagnosis of growth-plate injuries in young athletes may prolong symptoms and time away from activity, and possibly cause growth disturbances⁹.

Some features point away from Iselin's disease towards a more serious cause: fever or a child who is generally unwell, suspected infection (including a joint infection, called septic arthritis), a break in the skin or ulceration, or a suspected fracture¹¹.

What helps first?

Treatment usually starts without procedures. Conservative care is often the first approach for growth-plate stress injuries of the foot and ankle in young athletes⁹. For Iselin's disease it's described as rest, avoiding the activities that bring on the pain, ice, and anti-inflammatory medicines for pain⁵. A cast can be used for 2–4 weeks in some cases⁵. For overuse growth-plate injuries in young athletes generally, an extended period of active rest, with immobilisation (a cast or similar support) when necessary, is the most effective treatment⁷.

Physical therapy is also described: strengthening, stretching and balance exercises for the foot and ankle⁵. A shoe insert (an orthosis) with a small lift or wedge on the outer edge is described as helping to reduce stress on the peroneal muscles, the muscles along the outer side of the lower leg⁵.

Whichever treatment is chosen, an athlete should stay out of full sport until the symptoms have gone⁷. The treatments here are described options rather than proven fixes, because no studies have compared them in young athletes⁷.

What helps if that isn't enough?

The next steps build on the first ones: continued rest and offloading, then physical therapy, orthoses, or a short period in a cast⁵. While you try physical therapy, orthoses or taping, keep offloading the foot and avoiding the activities that provoke pain. A conservative approach centred on rest, offloading and symptom control can often lead to good results and avoid unnecessary surgery⁵. It isn't clear yet which step works best for Iselin's disease.

Surgery is often the next step for growth-plate stress injuries of the foot and ankle in young athletes that don't settle with non-surgical care, though when it's done and which operation is used vary⁹.

Symptoms that carry on despite conservative care can reflect a complication. One described complication is nonunion, where the growth centre doesn't join the bone¹⁰.

How long does it take, and can it come back?

The outlook is generally good. Iselin's disease is described as self-limiting, fading as growth completes, even though it can be treated². Symptoms typically settle when the growth centre closes, usually by 14–15 years of age⁵. How long it takes with care isn't clear yet.

Not every case settles cleanly. Some foot growth-centre problems leave persistent symptoms or deformity⁵. In some reported cases of Iselin's disease the growth centre didn't join the bone, and pain carried on into adulthood⁴¹⁰. Spotting and treating the condition early may help avoid lasting complications⁴.

Wait for symptoms to settle before a full return to sport⁷. It isn't clear yet whether Iselin's disease comes back or what prevents it. For young athletes in general, it can help to keep an eye on flexibility, strength, training volume and coaching style, because these can be changed and affect injury risk⁷.