Accessory navicular: the extra bone that is usually just along for the ride.
Up to one in five people have this bone. Almost none of them know. If yours has been blamed for your foot pain, read on.
An accessory navicular is an extra bone or piece of cartilage on the inner side of the foot, next to the navicular bone, present from birth in roughly 4 to 21 percent of people. The ATNS Index of Neuroplastic Symptoms describes it as usually of no significance, like many of the normal variants that show up on X-rays, and says that if pain is being attributed to it, neuroplastic symptoms should be assessed as part of a complete evaluation. Neuroplastic symptoms are real pain produced by a sensitized nervous system rather than by the structure on the scan. Most people with this bone never have pain, so when pain is present, the bone may be an innocent bystander, and an approach that addresses the brain's role exists.
This page is about understanding the condition and the role the brain and nervous system can play in it. It is not a diagnosis. Your own clinicians know your case.
What an accessory navicular is
The navicular is a boat-shaped bone on the inner side of the midfoot, where the main tendon that supports the arch attaches. In some people, a separate piece of bone or cartilage sits next to it. This is an accessory navicular, sometimes called an os naviculare or os tibiale externum. It is there from birth and is simply a variation in how the foot formed.
It shows up on X-rays and MRIs as an extra bone, and it can create a visible bump on the inner arch. Occasionally, especially in adolescents and after a twist or a period of overuse, the junction between the accessory bone and the main navicular becomes irritated and painful. That is sometimes called accessory navicular syndrome, and it usually settles with rest, supportive footwear and time.
The important point is scale. Far more people have the bone than ever have symptoms from it.
The neuroplastic contribution
The ATNS Index of Neuroplastic Symptoms files the accessory navicular alongside the many radiological variants of 'normal' that are usually of no significance. Its concern is what happens when a clinician points to the extra bone as the explanation for pain. When that happens, the index says, neuroplastic symptoms should be assessed as part of a complete evaluation.
Neuroplastic symptoms are real, physical symptoms produced by learned pathways in the brain and nervous system rather than by ongoing damage in the body. The brain decides how dangerous a body part is and produces pain to match. Being told there is an abnormal bone in your foot gives the brain a reason to treat the foot as fragile. Attention locks onto it, each step is monitored, the arch muscles guard, and the pain alarm becomes easier and easier to trip. This is sensitization, and it is not imaginary and not a character flaw. It is a learned protective pattern, and the brain that learned it can learn otherwise.
- The bone is real and has been there your whole life.
- Whether it is the pain generator is a separate question that imaging cannot answer.
- Related entries: flat feet pain and plantar fasciitis.
What the research shows
The literature on the accessory navicular is almost entirely about how common and how usually harmless it is. A meta-analysis of its prevalence and anatomy found a pooled rate of around 12 to 13 percent, with wide variation by ancestry, from about 8 percent in North American samples to nearly 40 percent in East Asian ones, and no effect of sex or imaging method.
A review of accessory ossicles of the foot and ankle reports the commonly cited overall range of 4 to 21 percent, states that the majority of accessory naviculars are asymptomatic and discovered incidentally after unrelated foot or ankle injuries, and notes that when the bone does cause pain it is most often in skeletally immature adolescents following overuse or trauma.
There is no research on central sensitization or neuroplastic pain in people with an accessory navicular specifically. The argument is the same one that applies to every common, mostly silent imaging finding: if most people with the finding have no pain, the finding alone cannot explain pain in those who do, and the wider science of persistent musculoskeletal pain, where a sensitized nervous system is a well-described driver, offers the most likely alternative when there is no injury or inflammation.
Signs the brain may be part of the picture
- You are an adult and the pain began without any injury or change in activity.
- There is no swelling, redness or warmth over the bone.
- The pain moves to other parts of the foot, or the other foot, or comes and goes unpredictably.
- It flares with stress, tiredness or worry more than with distance walked.
- Orthotics, rest and boots have been tried for months without lasting change.
- You have other sensitized-system symptoms: back pain, headaches, gut or pelvic symptoms, poor sleep.
Stand barefoot and reassign the bump
Stand barefoot on a firm floor for two minutes. Shift your weight slowly onto the inner edge of the painful foot and back to centre, five times. As sensation arises near the bump, describe it neutrally: pressure, warmth, pulling. Then say to yourself what the research says: one in eight people has this bone and almost none of them feel it. Let the arch muscles soften rather than brace. Finish by walking ten relaxed steps. You are teaching your brain that this part of the foot is ordinary, not fragile.
A solution that addresses it
An approach exists that addresses the brain's contribution: pain and symptom reprocessing. It begins with education about neuroplastic symptoms, so that an extra bone most people carry painlessly can be understood as unlikely to be what hurts. It uses somatic tracking (attending to foot sensation with curiosity instead of alarm), reducing fear and threat, a graded return to walking, standing and the activities you have been avoiding, emotional awareness and expression, and acceptance and commitment skills. Trained clinicians deliver it, and digital programs increasingly support daily practice.
Cindra is a daily AI companion built around these approaches, with daily check-ins, short practices and plain-language lessons for people whose symptoms have a neuroplastic component. If a normal variant on an X-ray has become the story of your foot, you can join the waitlist.
What to do next
Have the foot properly examined. A clinician should check for tenderness, swelling and tendon problems at the bone, look for stress fracture if you have increased training or have bone-density concerns, and consider other causes of inner-foot pain. Night pain, fever, a hot swollen joint or an inability to bear weight need prompt assessment.
If the examination finds only the bone, ask the direct question the index suggests: could my pain be neuroplastic? If the answer is 'possibly', begin learning why hurt does not mean harm and start a paced return to normal walking.
Questions people ask
Is an accessory navicular a neuroplastic condition?
The bone itself is a normal anatomical variant, not a condition. The ATNS index says that if pain is being attributed to it, neuroplastic symptoms should be assessed as part of a complete evaluation, because the bone is usually of no significance.
How common is an accessory navicular?
Reviews cite a range of 4 to 21 percent of people, and a meta-analysis found a pooled prevalence of about 12 percent. The large majority are found by chance and never cause symptoms.
Do I need surgery to remove it?
Surgery is occasionally done when the bone is clearly inflamed and conservative care has failed, most often in adolescents. For an adult with no swelling and a long history of variable pain, it is worth asking whether the bone is really the source before considering an operation.
Can it cause flat feet?
The accessory navicular is associated with a flatter arch in some people because of where the supporting tendon attaches, but flat feet are themselves common and usually painless. See our page on flat feet pain for more.
References
- The prevalence and anatomy of accessory navicular bone: a meta-analysis. PMC11405447
- Accessory Ossicles of the Foot and Ankle: Disorders and a Review of the Literature. PMC5786346
A daily companion for the hard days and the ordinary ones.
Cindra is an AI companion from Karuna Labs built around acceptance and commitment therapy and the science of neuroplastic symptoms. It checks in with you each day, helps you notice what your symptoms are pulling you away from, and nudges you back toward the things that matter. Cindra is invite-only while we build it with early members.
Join the waitlistThis article is for general education and is not medical advice, and it does not diagnose or treat any condition. Persistent symptoms deserve a proper medical assessment to rule out disease or injury before a neuroplastic explanation is considered. If your symptoms are new, changing, or come with red-flag signs such as fever, unexplained weight loss, numbness or weakness, chest pain, or loss of bladder or bowel control, see a clinician promptly.