Foot
Accessory Navicular
About Your Condition
An accessory navicular is an extra piece of bone on the inner side of the foot, adjacent to the navicular bone — the prominence on the inner arch. It is a normal anatomical variant present in approximately 10% of the population, but in some people it becomes painful through direct pressure from footwear, irritation at the junction between the accessory bone and the navicular, or because the tibialis posterior tendon — which attaches in this region — is placed under abnormal tension.
There are three types: Type I, a small sesamoid bone within the tendon, usually asymptomatic; Type II, a larger ossicle attached to the navicular by a fibrous or cartilaginous junction, which is the type most likely to become painful; and Type III, where the accessory bone is fully fused to the navicular, forming a prominent bony horn.
The accessory navicular and flat foot frequently coexist — the accessory navicular can contribute to tibialis posterior tendon dysfunction and thereby worsen arch collapse. Symptoms sometimes first appear after a twisting injury or direct knock to the inner foot, which tends to settle if well managed; when pain occurs alongside an established flat foot, it tends to respond less well to non-operative management.
Non-Operative Management
Non-operative management focuses on reducing direct pressure over the prominence and offloading the tibialis posterior tendon.
Footwear Modification
- Shoes that avoid direct pressure over the inner prominence are essential — soft uppers and a wide fit reduce friction and irritation.
- High-top or well-structured footwear that supports the ankle and arch can help reduce tendon stress.
- For those wanting to keep running or walking for exercise, a motion-control or stability jogger with strong medial arch support helps offload the tibialis posterior tendon.
Orthotics
- A medial arch support reduces the load on the tibialis posterior tendon and can significantly relieve pain — a custom orthotic with a specific medial arch contour is the most effective option, particularly if a flat foot is contributing.
- A doughnut-shaped pad placed around (rather than over) the prominence protects the area from direct shoe pressure.
Activity Modification and Rest
- Reducing high-impact activities during a flare-up allows local inflammation to settle.
- In acute presentations a period in a walking boot may be recommended.
When to Consider Surgery
Surgery is considered when symptoms significantly limit your daily activities despite an adequate trial of non-operative treatment, typically over three to six months.
The standard operation is excision of the extra bone with advancement of the tibialis posterior tendon, addressing both the accessory bone and the tendon attachment. In patients with a significant associated flat foot, this may need to be performed as part of a larger flatfoot reconstruction.