Fact-sheet: Accessory navicular syndrome
Updated on 11/18/2025 at 1:44 PM
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Definition
The accessory navicular is a supernumerary tarsal bone located posteriorly, derived from a secondary ossification center of the posteromedial tuberosity of the navicular bone
Accessory navicular syndrome results from microtrauma to the synchondrosis, causing acute or chronic pain on the medial aspect of the foot
Clinical features
4 to 21% of the general population, bilateral in 50 to 90% of cases
Mostly asymptomatic, an incidental finding on radiographs
Symptomatic mainly in adolescence and in women aged 40-50: pain localized to the medial aspect of the foot, sometimes with local swelling, which can cause a limp, particularly in children
Nuclear medicine
Accessory navicular syndrome (type II) causes mild, focal hyperemia of the medial border of the foot on bone scintigraphy and focal uptake on SPECT/CT
Management
First-line: NSAIDs
Second-line: local corticosteroid injection
Third-line: surgical excision
Classification
Type 1 accessory navicular bone: os tibiale externum or sesamoid bone of the posterior tibial tendon
- Small round or oval ossicle measuring 4 to 6 mm, not attached to the navicular bone, located 5 mm away, embedded within the posterior tibial tendon
- Well-defined, regular margins
- No joint space with the navicular bone
- 30% of accessory navicular bones
- Usually asymptomatic
Type 2 accessory navicular bone:
- Triangular or heart-shaped, up to 12 mm, attached to the navicular bone by a thick layer of fibrous tissue or fibrocartilage (synfibrosis or synchondrosis)
- Located on the posteromedial aspect of the navicular tuberosity. Fibers of the posterior tibial tendon insert here.
- Symptomatic: synchondrosis involvement (degenerative changes) and/or tendinopathy (posterior tibial tendon)
Type 3 accessory navicular bone: bony tuberosity in continuity with the navicular bone, on its posteromedial aspect
Differential diagnosis
Often mistaken for a navicular avulsion fracture via the posterior tibial tendon when incidentally found in a trauma setting