An 18-year-old female ballet dancer reports deep posterior ankle pain during full pointe work. Radiographs reveal a well-defined rounded ossicle behind the lateral tubercle of the talus. This ossicle most likely represents:

• A Os peroneum
• B Accessory navicular
• C Os vesalianum
• D Os trigonum ✓

Explanation

The os trigonum is a large accessory ossicle arising from a secondary centre at the posterolateral tubercle of the talus that fails to fuse with the body. Repetitive forced plantarflexion, as in pointe work, impinges it against the tibia and calcaneus producing posterior ankle impingement syndrome. The accessory navicular lies at the medial tuberosity of the navicular, and os peroneum sits in the peroneus longus tendon at the cuboid tunnel.

Reference: Gray's Anatomy, 42nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.