Accessory Navicular Syndrome: Extra Bone Pain 2026 | DPM

Type	Description	PTT Attachment	Symptoms	Treatment
Type I (os tibiale externum)	Sesamoid bone in PTT; completely separate; ~1–2mm	None — embedded within PTT	Usually asymptomatic; incidental finding	Conservative; surgery rarely needed
Type II (synchondrosis)	Large (8–12mm) ossicle connected to navicular by fibrocartilage; most symptomatic	Partial — PTT attaches to accessory bone AND navicular	Medial midfoot pain; prominence; flatfoot acceleration	Conservative 3–6 months; Kidner procedure if fails
Type III (cornuate navicular)	Fused accessory navicular; enlarged navicular tuberosity	Full PTT attachment to enlarged tuberosity	Mild medial prominence; usually less symptomatic	Conservative; exostectomy if bony irritation

Treatment	Indication	Success Rate	Notes
Activity modification + NSAIDs	First-line all types	50–60% acute resolution	Reduce aggravating activities 4–6 weeks
Custom orthosis (UCBL / medial arch)	All symptomatic types; flatfoot component	60–75%	Arch support reduces traction on synchondrosis
Cast / boot immobilization	Acute flare; failed orthotics	65–75%	4–6 weeks; allows synchondrosis inflammation to resolve
Corticosteroid injection	Persistent bursal irritation; failed above	50–65%	US-guided; periosteal / bursal; not into PTT
Kidner Procedure	Type II; failed 6 months conservative	80–90% pain relief	Excise accessory navicular; advance PTT to navicular; 6–8 weeks NWB
Modified Kidner + flatfoot reconstruction	Type II with flatfoot deformity; PTT dysfunction	85–90%	FDL transfer + calcaneal osteotomy added if significant flatfoot

Quick answer: Accessory Navicular Syndrome Extra Bone Foot Pain has multiple potential causes including mechanical, neurological, vascular, and inflammatory. The most common causes we identify are overuse, ill-fitting shoes, and biomechanical imbalance. Red flags requiring urgent evaluation: warmth/redness (infection), inability to bear weight (fracture), and unilateral swelling without injury (DVT). Call (810) 206-1402.

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An accessory navicular is an extra piece of bone (or sometimes cartilage) located on the medial (inner) side of the navicular bone in the midfoot. Present in approximately 10–12% of the population, the accessory navicular is a congenital variant — not caused by injury — that develops as a secondary ossification center fails to fuse with the main navicular during childhood. Most people with an accessory navicular have no symptoms. But a significant minority — particularly active teenagers and young adults — develop accessory navicular syndrome, a painful condition that can significantly impair daily activity and athletic participation.

Types of Accessory Navicular

Type I (Os Tibiale Externum): A small, rounded sesamoid bone within the posterior tibial tendon. Usually asymptomatic. Incidental finding on X-ray.

Type II: The accessory bone is connected to the navicular by a fibrocartilaginous synchondrosis. This is the type that most commonly becomes symptomatic — the fibrocartilage junction is susceptible to stress and disruption, causing pain. The posterior tibial tendon inserts partially into the accessory bone, which can alter its function.

Type III (Cornuate Navicular): The accessory bone has fused directly with the navicular, forming a single enlarged, horn-shaped bone. Usually asymptomatic but may cause shoe irritation due to its prominence.

Symptoms and Who’s Affected

Accessory navicular syndrome most commonly presents in adolescents and young adults — the peak onset is during the growth spurt, typically ages 10–16. Flat feet (pes planus) and hypermobile flatfoot are strong risk factors, as pronation increases tension on the posterior tibial tendon at the accessory bone insertion. Symptoms include a visible and palpable bony prominence on the inner midfoot, direct tenderness over the navicular, aching or sharp pain with activity and direct shoe pressure, and sometimes swelling over the bump. Symptoms are often triggered or worsened by a specific injury (ankle sprain, direct blow), new athletic activity, or a growth spurt.

Conservative Treatment

Non-surgical management is the first line for accessory navicular syndrome. Custom orthotics with medial arch support reduce pronation and offload the accessory navicular–tibial tendon junction. A walking boot provides rest and immobilization during acute flares. NSAIDs control inflammation during symptomatic periods. Physical therapy strengthening the posterior tibialis and hip abductors reduces medial foot loading. Donut padding or silicone pads protect the bony prominence from shoe friction. Most patients respond to conservative management — studies report 50–89% success with non-surgical care.

Surgical Treatment: The Kidner Procedure

When conservative treatment fails after 3–6 months, the Kidner procedure provides reliable relief. The accessory navicular is excised, and the posterior tibial tendon — which was attaching partially to the accessory bone — is advanced and reattached to the main navicular in a more plantar, biomechanically optimized position. This eliminates the painful synchondrosis, removes the bony prominence, and may actually improve posterior tibial tendon function. Recovery involves 4–6 weeks in a cast or boot, followed by physical therapy. Return to sport typically occurs at 3–4 months. Success rates exceed 85–90%.

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In-Office Treatment at Balance Foot & Ankle

If home treatment isn’t providing relief for your accessory navicular syndrome extra bone foot pain, our podiatry team at Balance Foot & Ankle can help with same-day evaluations and advanced in-office care.