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Small bones which can become dislodged in the joint, causing inflammation and pain. They can be displaced through a sudden injury, or through stress injuries (repetitive movement).

What is it?

Ossicles are small bones. The ossicles which occur in the ankle are accessory ossicles - extra bones which form naturally during the development of the skeleton. The most common accessory ossicle in the ankle is the Os trigonum, which occurs in about 5-10% of all people. It forms next to the talus (or anklebone).

Ossicles can cause a problem if they are displaced and cause pinching in the ankle. They can be displaced through a sudden injury, or through stress injuries (repetitive movement). They can also be a problem if the surrounding tissue is damaged, and thickens or swells up to push against the ossicle or other surrounding tissues.

How does it feel?

Pain in any part of the ankle could be indicative of impingement caused by an ossicle. You may also feel instability in your ankle. Os trigonum (see above) will cause pain behind the heel of deep in the back of the ankle. Pain is usually worse when the ankle is pointed downwards. You may also feel a painful clicking sensation when your foot is twisted in and out.


Impingement relating to ossicles can usually be detected with an x-ray or an MRI scan. Thickened or swollen tissue can also be detected on an MRI scan. It might also be necessary for the surgeon to use arthroscopic diagnosis.


Some smaller ossicles are is removed using arthroscopic surgery, while the os trigonum is usually removed using minimally invasive surgery. For the latter, a combination of small incisions are made at the back of the ankle and the os trigonum is carefully removed using a scalpel. Any thickened or damaged soft tissue will be also be removed or repaired during the operation.


After an os trigonum operation, you will be in a splint for two weeks, and have physiotherapy for the next two or three months. Usually, after surgery, weight-bearing will be possible immediately after the operation, but this is dependent on the location of the ossicle and the amount of soft tissue repair that was necessary.

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