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Os Naviculare (Accessory Navicular)

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An os naviculare (or accessory navicular) is an extra bone or piece of cartilage on the inner side of the foot, just above the arch. It is found in around 10–15% of the population and is a normal anatomical variation, but can become painful — particularly in adolescence or after injury or overuse.

Symptoms

• Pain and swelling over the inner arch
• Tenderness when wearing tight shoes or boots
• Flattening of the arch or flatfoot appearance
• Pain that worsens with activity

Causes

• Repetitive stress or overuse (running, ballet, sports)
• Direct trauma or sprain
• Tight or ill-fitting footwear
• Underlying flatfoot or posterior tibial tendon dysfunction

Non-Surgical Treatment

• Activity modification
• Supportive, cushioned footwear
• Custom orthotics to offload the bony prominence
• Ice and anti-inflammatory medications
• Physiotherapy to strengthen surrounding muscles
• Immobilisation in a boot or cast for 2–4 weeks in severe cases
• Steroid injection for persistent cases

Surgery — Kidner Procedure

When conservative management fails, the most commonly performed procedure is the Kidner procedure, where the accessory navicular is removed and the posterior tibial tendon is reattached to the native navicular bone.

In many cases, a calcaneal osteotomy (heel shift) is also performed to realign the foot and offload the medial arch. Performed as a day case under general anaesthetic.

Recovery

Timeframe	What to Expect
0–6 weeks	Non-weight-bearing in cast. Foot elevated.
6 weeks	Cast removed. Transition to boot. Begin weight-bearing.
6–12 weeks	Progressive physiotherapy. Swelling may persist.
12 weeks+	Return to full activity if pain-free.