Ankle instability

Instabilité de cheville

What is it?

Ankle instability is defined as painful ankle laxity and results from repeated trauma to the various external ligaments of the ankle. The external structure is composed of three ligaments that provide stability to the joint when the ankle is moving while preventing excessive bone movement. When the ankle is strained, these can be stretched, partly torn or completely severed.

Ligaments externes de la cheville
  • Fig. 1

    External ankle ligaments

    1. Anterior talofibular ligament
    2. Calcaneofibular ligament
    3. Posterior talofibular ligament

Although 90% of sprains usually heal spontaneously, ligaments can sometimes heal but remain extended, which means they no longer function as stabilisers. In this case, some risky movements are no longer constrained by ligaments and sprains occur more easily, often during mundane activities such as walking or going down stairs. Beyond the pain related to this type of trauma, an unstable ankle is at high risk of further complications during sprains (fractures, cartilage and tendon damage, etc.) or sometimes develops into severe arthritis.

  • Fig. 2

    Normal ankle. Ligaments under tension

Cheville normale, ligaments sous tension
Cheville instable, ligaments détendus et incompétents
  • Fig. 3

    Unstable ankle, stretched and incompetent ligaments.

Clinical presentation

Patients suffering from instability generally report an impression of the ankle giving way and the sensation that it does not “stay in place”. Patients often fear performing risky activities. When investigating the trauma history, patients always report several episodes of sprains. These sprains occurred increasingly frequently and generally involved minor injuries.


Other causes for sprains are always investigated such as:

  • Generalised laxity (hyper-laxity)
  • imbalanced muscles
  • a shortening of the Achilles tendon (gastrocnemius equinus)
  • a structural abnormality of the hindfoot (hindfoot varus or high arches)
  • Performing high-risk activities (sports involving swivelling movements, physical work, etc.)

It is very important to highlight other injuries that may accompany instability such as tendon injuries or external signs of ankle conflict.

When should you consult a specialist?

Hypermobility (hyper-laxity) is not in itself a reason for treatment. It is advisable to see a specialist when this condition is accompanied by pain, when suffering from recurrent sprains or following a sprain episode.

It is important to understand that a sprain treated inadequately significantly increases the risk of instability complications.

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