Accessory Navicular Syndrome

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Expert Patient Guide  ·  London & North London

Accessory Navicular Syndrome

A comprehensive patient guide by Mr Matthew Welck, Consultant Orthopaedic Foot & Ankle Surgeon, Royal National Orthopaedic Hospital (RNOH) Stanmore and UCL — London, UK.

At a Glance: Accessory Navicular Syndrome

ConditionAn extra bone on the inside of the foot that becomes painful. It sits where a strong tendon (the tibialis posterior) attaches to the navicular, one of the bones of your arch.
How CommonAbout 1 in 5 people have the extra bone. Only a small number of them ever get pain from it.
Who It AffectsMost often teenagers and young adults, especially girls and young women, and people who play a lot of sport.
Typical SymptomsAching and a bony lump on the inside of the arch, worse with sport and stiff shoes. Some people also have a flat foot.
DiagnosisX-rays and a CT scan taken while you are standing, and an MRI scan.
Non-Surgical CareRest, different shoes, insoles, physiotherapy, a spell in a boot, anti-inflammatory painkillers.
Surgical OptionsRemoving the extra bone, the Kidner / modified Kidner operation, and operations that also correct a flat foot.
OutlookMost people get better without an operation. If surgery is needed, the modified Kidner operation gives very good, reliable results.
SpecialistMr Matthew Welck — Consultant Foot & Ankle Surgeon, RNOH Stanmore & UCL, London. matthewwelck.com

01

What Is Accessory Navicular Syndrome?

An accessory navicular is an extra bone on the inside of the foot. It sits next to the navicular — the bone at the top of your arch — and inside or beside the tibialis posterior tendon, the strong cord that holds your arch up as you walk. You are born with it. About one person in five has one, and most never know it is there.

“Accessory navicular syndrome” is the term used when that extra bone becomes painful. The pain usually comes from the soft, gristly join between the extra bone and the main navicular becoming irritated, or from strain where the tendon attaches. Seeing a specialist foot and ankle surgeon — such as Mr Matthew Welck in London — means you get the right diagnosis and all the treatment choices explained to you.

The three types

  • Type I: a small, separate piece of bone inside the tendon that is not joined to the navicular. It usually causes no symptoms.
  • Type II: the type that most often causes pain — the extra bone is joined to the navicular by a soft, gristly bridge that can be strained or inflamed. This is the type that most often needs treatment.
  • Type III: the extra bone has joined onto the navicular, leaving a pointed bump that can rub on your shoes.
Good to know: an accessory navicular is common — around one in five people have one, and the great majority never have any symptoms from it.

02

How Common Is It in the UK?

The accessory navicular itself is common: about 20–30% of people have one, making it one of the most common extra bones in the foot. In most people it never causes any trouble.

Only a small number become painful, and this usually starts in the teenage years — often in girls and young women, and in active people whose sport and shoes put strain on the inside of the arch. Because this often happens during a busy sporting time of life, it is frequently mistaken at first for a sports injury that will not settle.

03

What Causes Accessory Navicular Syndrome?

You are born with the extra bone, but it only becomes painful when something strains or irritates it. Common triggers include:

  • Doing too much, too often — running, dancing, football and other sport that repeatedly pulls on the tendon.
  • An injury — an ankle sprain or twist can set off pain in an extra bone that had never caused trouble before.
  • Pressure from shoes — stiff or tight shoes, boots and skates rubbing on the bony lump.
  • Flat feet — many people also have a flexible flat foot, which pulls harder on the tendon where it attaches.
  • Growing — during the teenage years the soft join between the bones is still developing and strains easily.

04

What Are the Symptoms?

  • Pain on the inside of the arch and the middle of the foot, worse with walking, standing and sport
  • A visible, tender bony bump on the inside of the foot, just below and in front of the ankle
  • Redness or rubbing where the lump presses on your shoe
  • A flat or dropping arch in some people
  • Aching after activity that eases with rest but returns with exercise
  • Trouble wearing stiff or narrow shoes, skates or ski boots

05

What Investigations Might You Need?

  • X-rays taken standing up — the first test. These show the extra bone, which type it is, and the shape of your arch under your own weight.
  • Standing CT scan (WBCT) — a modern, low-dose 3D scan taken while you stand. It shows the exact size and position of the extra bone and how it sits against the bones around it. It is used routinely at specialist centres such as the RNOH and is Mr Welck’s usual practice.
  • MRI scan — to show whether the join between the bones is inflamed, and to check the condition of the tendon.
  • Examination in clinic — to find exactly where your foot is tender, test the strength of the tendon and look at the shape of your arch.

06

Non-Surgical Treatment Options

Most people start here, and most get better without an operation — especially younger patients, whose symptoms often settle as they finish growing:

  • Changing your activities and resting from any sport that makes the pain worse
  • Supportive shoes and padding to take pressure off the bony lump
  • Made-to-measure insoles or arch supports, especially if you also have a flat foot
  • Physiotherapy to strengthen the tendon and calf muscles that support your arch
  • A short spell in a walking boot or cast to settle things down when the pain is severe
  • Anti-inflammatory painkillers and ice when the pain flares up
  • Occasionally an injection, guided by ultrasound, for a small number of carefully chosen patients

07

Surgical Options

Surgery is only considered when other treatments have not controlled the pain. The right operation depends on your age, how active you are, which type of extra bone you have and whether you also have a flat foot — so the plan is different for everyone.

Simple Excision

The extra bone is taken out through a small cut on the inside of the foot, and the tendon is left where it is. It is a simple, well-established operation that works well for the right patient.

Kidner / Modified Kidner Procedure

The extra bone is taken out and the tendon is re-attached to the navicular, so that it pulls on your arch in a more natural way. This is the most common operation for this problem worldwide. Research shows it gives very good, reliable pain relief and good function, with one of the lowest rates of problems of any technique — which is why it is the preferred operation for most people with a painful accessory navicular.

Correcting an Associated Flat Foot

If you have a flexible flat foot as well as a painful extra bone, the flat foot may need correcting at the same time — for example with a small implant placed in the foot, or by re-shaping a bone — so that the tendon and the repair are not put under too much strain afterwards. A standing CT scan is especially helpful for planning this accurately.

A note on other techniques: other operations — joining the extra bone onto the navicular, or drilling across the join — have been used, but research shows the bones are less likely to heal together and there are more complications, so these are used far less often. Mr Welck will talk you through why one approach is recommended for you over another.

08

Why Choose Mr Welck?

Mr Matthew Welck is a Consultant Orthopaedic Foot & Ankle Surgeon at the Royal National Orthopaedic Hospital (RNOH) Stanmore — one of the UK’s leading tertiary orthopaedic centres — and Honorary Associate Clinical Professor at UCL.

He treats foot and ankle problems only, in both children and adults — from arch and tendon problems through to total ankle replacement, complex reconstruction, redo surgery and sports injuries — including tendon conditions such as Achilles tears and Achilles rupture. He has written over 50 published research papers, has completed two specialist fellowships including training abroad, and has led the way in using standing CT scans and 3D-printed guides made for each individual patient in complex surgery.

Patients are seen across London and North London, with quick access to MRI and standing CT scans and to a wider team of specialists. Every option is explained openly, and you agree a plan together that is right for you. Visit matthewwelck.com to learn more.

09

Frequently Asked Questions

What is an accessory navicular?

It is a common extra bone on the inside of the foot that you are born with. It sits next to the navicular bone, inside or beside the tibialis posterior tendon. About one person in five has one, and most never have any symptoms.

Is accessory navicular syndrome serious?

No — it is not dangerous and does not damage the rest of the foot. It is, however, a common cause of ongoing pain on the inside of the arch in teenagers and active adults, and it can be treated well.

Do I need surgery for a painful accessory navicular?

Usually not. Most people get better with rest, different shoes, insoles and physiotherapy, and younger patients often improve as they finish growing. Surgery is only used when the pain does not settle with these treatments.

What is the Kidner procedure?

It is an operation that removes the extra bone and re-attaches the tendon to the navicular, restoring the natural support for your arch. The modified Kidner is the most commonly performed operation for this condition and has the best evidence behind it.

How long is recovery after accessory navicular surgery?

Expect a spell in a boot or cast, then a gradual return to normal activity. Most people are walking comfortably within a few months and back to sport once their strength and confidence return. Mr Welck will give you a timeline for your own operation.

Is accessory navicular linked to flat feet?

Often, yes. Many people also have a flexible flat foot, which pulls harder on the tendon. If that is the case, correcting the flat foot at the same time can protect the result of surgery.

Can my child play sport with an accessory navicular?

In most cases yes, once the pain is under control. A short rest, the right shoes or insoles and the right physiotherapy exercises usually allow a return to sport. Seeing a specialist helps rule out anything that needs more attention.

Where can I see Mr Matthew Welck for accessory navicular treatment in London?

Mr Welck consults across North and Central London. NHS patients are seen at the Royal National Orthopaedic Hospital (RNOH) Stanmore. Private appointments can be booked on 07547 395270 or by emailing secretary@matthewwelck.com.

10

Book a Consultation

If you or your child has ongoing pain and a tender bump on the inside of the arch, seeing a specialist can make a real difference to recovery and to getting back to sport.

Book a private or NHS consultation with Mr Matthew Welck, Consultant Foot & Ankle Surgeon. Being seen early by an expert gives you the widest choice of treatments and the best long-term result.

  • Email: secretary@matthewwelck.com
  • Call: 07547 395 270
  • Website: matthewwelck.com

This guide is for general information and does not replace individual medical advice.

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Written by: Matthew Welck | Consultant Orthopaedic Foot & Ankle Surgeon London — last updated September 2026

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