Accessory Ossicles of the Foot: Os Naviculare, Os Peroneum, and Others

Medically reviewed by Dr. Tom Biernacki, DPM — Board-Certified Podiatric Surgeon — Balance Foot & Ankle, Howell & Bloomfield Hills, MI. Last updated April 2026.

Accessory ossicles of the foot — secondary ossification centers that fail to fuse with adjacent bones during skeletal development — are common anatomical variants present in 10–40% of the population depending on the ossicle. Most accessory ossicles are incidental findings on foot X-ray that are completely asymptomatic and require no treatment; however, a subset become symptomatic from direct pressure, mechanical impingement, or stress fracture through the synchondrosis, and understanding the relevant anatomy and pathological conditions associated with each ossicle is essential for accurate diagnosis.

Os Naviculare (Accessory Navicular)

The most clinically important accessory ossicle — present in 4–12% of the population; three types: Type I (os tibiale externum) — a small, rounded ossicle within the posterior tibial tendon substance proximal to the navicular; Type II (the most common symptomatic type) — a large accessory ossicle connected to the navicular by fibrocartilaginous synchondrosis (the navicular tuberosity is enlarged and bipartite); Type III (cornuate navicular) — a completely fused variant producing a prominent navicular tuberosity. Type II symptoms: medial midfoot pain at the navicular prominence from direct shoe pressure; the synchondrosis between the accessory ossicle and the navicular is subjected to shear from posterior tibial tendon forces — synchondritis produces pain indistinguishable from PTT tendinopathy; management: wide accommodative footwear, custom orthotics with navicular relief; surgical excision (Kidner procedure — excision of the accessory ossicle with advancement of the PTT insertion) for refractory cases.

Os Peroneum, Os Trigonum, and Others

Os peroneum: located within the peroneus longus tendon at the cuboid notch; present in 10–20%; os peroneum syndrome — symptomatic pain at the lateral plantar foot when the ossicle fractures or the synchondrosis becomes painful from peroneus longus tendon injury; a fractured os peroneum may indicate a peroneus longus tendon tear requiring surgical evaluation. Os trigonum: accessory ossification center of the posterior talar process (7–25%); posterior ankle impingement in plantar flexion — the primary cause of os trigonum syndrome in dancers (described in detail in posterior ankle pain topics). Bipartite sesamoid: discussed in sesamoid topics — the developmental variant of the tibial sesamoid must be distinguished from fracture (no bone marrow edema in bipartite). Os supranaviculare, os intermetatarseum, accessory cuboid: less common variants that may cause local pain at the site of their prominence or synchondrosis. Dr. Biernacki at Balance Foot & Ankle evaluates symptomatic accessory ossicles with weight-bearing X-ray and MRI and distinguishes accessory ossicle synchondritis from other causes of foot pain. Call (810) 206-1402 at our Bloomfield Hills or Howell office.

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Frequently Asked Questions

When should I see a podiatrist?

See a podiatrist for any foot or ankle pain that persists more than 2 weeks, doesn’t improve with rest, limits your daily activities, or is accompanied by swelling, numbness, or skin changes. People with diabetes or circulation problems should see a podiatrist regularly even without symptoms.

What does a podiatrist treat?

Podiatrists diagnose and treat all conditions of the foot, ankle, and lower leg including plantar fasciitis, bunions, hammertoes, toenail problems, heel pain, nerve pain, diabetic foot care, sports injuries, fractures, and foot deformities — both surgically and non-surgically.

What can I expect at my first podiatry visit?

Your first visit includes a full medical history, physical examination of your feet and gait, and in-office diagnostic imaging if needed (X-rays, ultrasound). We’ll discuss your diagnosis and create a personalized treatment plan. Most visits take 30–45 minutes.

Need Treatment at Balance Foot & Ankle?

Dr. Tom Biernacki, Dr. Carl Jay, and Dr. Daria Gutkin see patients at our Howell and Bloomfield Township offices.

Book Online or call (810) 206-1402

Accessory Bone Evaluation in Michigan

Balance Foot & Ankle evaluates symptomatic accessory ossicles of the foot including os naviculare and os peroneum. Our podiatrists determine when conservative care or surgical excision is needed.

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Clinical References

1. Coskun N, et al. Prevalence of accessory ossicles of the foot. J Am Podiatr Med Assoc. 2009;99(2):124-127.
2. Keles-Celik N, et al. Accessory ossicles of the foot and ankle: disorders and a review. Clin Anat. 2006;19(5):462-468.
3. Mellado JM, et al. Accessory ossicles and sesamoid bones of the ankle and foot. Eur Radiol. 2003;13(Suppl 6):L164-L177.