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Accessory Navicular Syndrome

Paediatric Foot Conditions· Also known as: painful accessory navicular, accessory navicular, os tibiale externumUpdated Nov 2026

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At a Glance

It is a spare bone on the inside of the foot that is there from birth. Roughly 4 to 21 in every 100 people have one. Most never notice it, and it is usually harmless. In a small minority it becomes painful, and this is called accessory navicular syndrome. When it hurts, it shows up as a sore lump on the inner middle of the foot, sometimes red or swollen. Treatment begins with non-surgical care, and an operation is only for pain that persists.

What is it?

An accessory navicular is an extra small bone on the inner side of your foot, next to the navicular bone (a bone on the inner side of the midfoot). It is the most common extra bone in the foot. People are born with it, because it forms differently as the foot grows.

The extra bone can take different forms, which are sometimes grouped into two main patterns and sometimes into three types. It may lie inside the posterior tibial tendon (a tendon along the inside of the ankle), or it may be a separate piece of bone next to the navicular. Either way, it is usually a harmless variant, a normal difference in how a foot is built.

Most people never know they have one. It becomes accessory navicular syndrome only when it causes pain, for example after an injury or when it is irritated. If it was found by chance on an X-ray and causes no pain, it usually needs no treatment.

Who does it affect?

The extra bone is common. About 4 to 21 per cent of people have one, and in children the figure is about 10 to 12 per cent. Most are found by chance, because most cause no trouble at all.

Only a small number of people have pain from it. About 1 in 100 patients with an accessory navicular have symptoms, and symptoms are reported in about 1 in 1000 adults.

When it does hurt, symptoms often start in the teenage years, and it is a common cause of pain on the inner side of the foot in teenagers, especially those who play sport. It is a common cause of pain on the inner side of the foot at that age.

The extra bone also seems to be found more often as people get older. It becomes more common from about age 40, and is most common in people aged 51 to 60, at 29.7 per cent.

Signs and symptoms

The main sign is a tender bump on the inner midfoot, around the navicular bone. The area may also look red or swollen. The pain or discomfort can be short-term (acute) or long-term (chronic), or it can flare up on top of a longer-running ache.

The pain is usually worse when you walk, play sport or wear shoes that press on the bump. Turning the foot outwards or pointing it down may also make the pain worse. The bump is usually easy to feel.

They tend to come and go and are related to activity.

Some signs need action: see 'When to see a podiatrist'.

What causes it?

The extra bone doesn't always hurt, and it isn't clear yet why some people get pain and others don't. Pain is thought to come from a few sources of stress on the bump.

Shoes can rub on the bump and irritate it. In children, shoe pressure is the most common cause of symptoms. The posterior tibial tendon (the tendon along the inside of the ankle) may also pull harder when the extra bone is there, which can strain the area. Friction at the joint between the extra bone and the navicular may irritate the bone as well.

Overuse and twisting injuries can set off pain too. Adults more often develop symptoms after a twisting injury to the foot.

Flat feet are often seen with a painful extra bone. A lowered arch may add stress to the bone, and the extra bone may also help lower the arch. Which comes first isn't clear, so don't assume that treating one will fix the other.

It tends to run in families, so ask your family about the extra bone or flat feet. It helps to note which activities, shoes or injuries bring on the pain, and to share this with your podiatrist.

How is it diagnosed?

Your podiatrist will ask when the pain began and which shoes and activities bring it on. They will compare both feet, feel the bump on the inner midfoot, and check for tenderness, warmth, swelling and redness.

An X-ray usually follows, and sometimes a CT or MRI scan. It is one part of the picture, because the extra bone is often a chance finding, so it is matched with your symptoms and the examination.

Inner foot pain has other causes. The main one to tell apart is a broken bone, which tends to cause more spread-out tenderness, often with bruising, and sharp, uneven edges. Others include a stress fracture, arthritis and a torn tendon. A child's limp has other causes too, such as hip problems, so it isn't always the extra bone.

Treatment

Treatment starts without surgery. Surgery is kept for pain that doesn't settle. These steps suit pain that has been checked and is thought to come from the extra bone.

Looking after it at home

Ease off the activities that bring on the pain, such as certain sports, for a period. Then build back up gradually. Ice may help settle a sore, tender bump.

Choose well-fitting, supportive shoes that don't press on the bump.

Treatment from your podiatrist

Your podiatrist may suggest shoe inserts, either arch supports or custom-made insoles. They lift the arch and take pressure off the bump, which sometimes improves symptoms. Physiotherapy is often part of care too. It isn't clear yet which type of exercise or length of treatment works best.

Other options

A walking boot or plaster cast is sometimes used for two weeks. If one is suggested, follow your clinician's advice on how long to wear it.

Surgery

Referral to an orthopaedic or foot and ankle specialist may be offered if pain continues after a reasonable trial of non-surgical care. Operations include removing the extra bone, drilling, and the Kidner procedure. Surgery has well-described benefits when it is needed. If you also have flat feet, they are usually dealt with at the same time as the extra bone.

Recovery

In growing children, the type of extra bone appears to change as the skeleton matures, and Type II bones are likely to develop into Type III over time. Over time, some bones join (fuse) to the navicular. Fusing doesn't always mean the pain has gone. Girls and children with a higher body mass index may be more likely to have a bone that doesn't fuse, though it isn't clear whether these cause it.

How long recovery takes isn't clear yet. Return to sport gradually. Ask your podiatrist how long to keep up shoe inserts or exercises.

Preventing it

It isn't clear yet what stops a painful extra bone from happening or coming back. For children's feet in general, it helps to choose suitable, well-fitting, supportive shoes and to keep weight in a healthy range while the arch is developing. It isn't clear yet whether this stops symptoms coming back.

When to see a podiatrist

When to book

Book an appointment with your podiatrist if:

your pain hasn't improved after a few weeks of home care
your symptoms keep coming back
you can't find comfortable shoes, or a lump or bump on your foot makes shoes hard to wear

When to get help sooner

Get urgent medical assessment (see your GP today, or go to an urgent care clinic or the nearest emergency department) if:

your child has a fever with a limp or a painful, red, hot or swollen joint, or seems very unwell with foot or leg pain: go straight away, without waiting for an appointment
your child suddenly has severe pain in one joint and is limping
you can't put weight on your foot or take four steps after an injury
you think you may have broken a bone in your foot or ankle in an injury, for example you heard a crack, or it swelled or bruised badly within minutes
your child has hurt their foot or toe and it may be broken (in children a break can look like a sprain)

See your GP soon if:

you have pain at night or at rest that doesn't settle
your child has a limp that hasn't improved after a week, limps without pain, or doesn't want to put weight on their foot

See your podiatrist or GP soon if:

your pain is getting worse, or doesn't settle with rest, less activity or pain relief

Frequently asked questions

Is an accessory navicular dangerous?

No. It is usually harmless, just a normal variation in how a foot is built. It only matters if it becomes painful. If it does, see the section 'When to see a podiatrist'.

Can I take anti-inflammatory medicines for the pain?

Anti-inflammatory medicines are sometimes part of care. Ask a doctor or pharmacist before using them, especially for a child, so they can check that they suit you or your child.

What should I ask a surgeon before an operation?

Ask which operation is planned and why. Also ask about the risks, what rehabilitation involves, and when sport can restart. Writing your questions down before the visit can help you remember them.