Foot problem

Posterior Ankle Impingement

Pain behind the ankle (Os Trigonum):

What is posterior ankle impingement?

The anklebone (talus) sits on the heelbone (calcaneus), forming a secondary joint in the ankle (the subtalar joint). At the back of the anklebone are two small bony lumps (tuberosities), one on the inside and one on the outside. In about 15% of people, the outside lump is naturally separated from the talus, and is called the ostrigonum.

Causes of pain behind the ankle:

The ostrigonum can cause problems in people who regularly point their feet downwards sharply – it’s most common in ballet dancers. When the ostrigonum gets sandwiched between the bottom edge of the shinbone (tibia) and the top surface of the heel bone, the tissues above and below the ostrigonum can become trapped, leading to inflammation and swelling.

The condition is known as posterior impingement.

Symptoms of posterior ankle impingement:

Posterior ankle impingement can cause tenderness by the anklebone on the outside of your leg. Pain is usually worse when your foot is pointed down. You may also feel a painful clicking sensation as your foot is twisted in and out.

Diagnosing posterior ankle impingement:

Posterior ankle impingement can be diagnosed by X-rays and an MRI scan may be used in combination to help confirm the underlying diagnosis.


In a small number of cases if the chemical is not effective or this procedure is not suitable, the section of nail root can be surgically removed and closed with sutures.

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Thoughts and advice on foot health care from the Podogo team.