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Ankle Instability

Ankle Instability


Ankle instability or laxity is a condition in which the ankle has too much motion (“looseness”) and easily “gives out.” Other joints in the foot such as the subtalar joint (the joint directly below the ankle) may also be involved. Some people have looseness in multiple joints due to genetic conditions.

In some instances, the ankle may give out even though the ligaments are stable. This is referred to as “functional instability” and may be due to tightness in the Achilles tendon or pain.


Patients with ankle instability have a variety of symptoms. Commonly, they complain of their ankle twisting easily, especially on uneven ground or during activities that involve turning or changing direction quickly, such as basketball. As the ankle ligaments become chronically damaged, you may actually experience less pain with these twisting episodes as it takes less energy (and injury) to roll the ankle.

Chronic instability may cause the ankle bones to move excessively with daily activities. Some patients, particularly after modifying their activities, will have fewer sprains but continue to have pain. Changes to the ankle’s stability even without recurrent injuries can cause pain. Downhill walking can be particularly painful as this predisposes the ankle bones to shift out of place.


The most common cause of ankle instability is recurrent ankle sprains. While most ankle sprains heal with non-surgical treatment, repeated sprains may cause the ligaments to heal stretched-out and lose their ability to provide stability.


There are multiple ligaments in the ankle. Ligaments in general are the structures that connect bone to bone and act like rubber bands. Tendons, on the other hand, connect muscle to bone and allow the muscles to exert force on their associated bones. In the case of an ankle sprain, there are several commonly sprained (torn) ligaments. The two most important are the following:

  1. The anterior talofibular ligament (ATFL), which connects the talus to the fibula on the outside of the ankle.

  2. The calcaneal fibular ligament (CFL), which connects the fibula to the calcaneus.

There is a third ligament that is not torn as commonly. It runs more in the back of the ankle and is called the posterior talofibular ligament (PTFL). 


These types of injuries are often called low ankle sprains. This is different than a high ankle sprain, which is a more severe type of ankle sprain involving ligaments that connect the tibia (long bone on the inside of the leg) to the fibula (bone on the outside of the leg).

If a patient has a high-arched [“cavovarus”] foot, this can predispose them to repeated ankle sprains. Furthermore, this foot shape puts the peroneal tendons which help support the ankle ligaments at risk for tearing and weakness.


foot and ankle orthopaedic surgeon can diagnose ankle instability by studying your medical history and performing a physical exam. During the exam, your surgeon will test the strength and motion in your joint. They will perform tests to check how loose your ankle is. They may order standing X-rays to check for any ankle arthritis or changes in your bone alignment that may have developed due to the instability. Stress X-rays may be used to show the amount of looseness present. While an MRI doesn’t show ankle looseness, it can be helpful to rule out other associated problems such as cartilage damage and tendon tears.


Your foot and ankle orthopaedic surgeon will determine the best course of treatment based on your pain and limitations on your day-to-day activities.

Non-surgical Treatment

If you have modest instability with no other symptoms, you may not need surgery. Non-surgical treatment options include bracing of the ankle for "at-risk" activities (such as running, basketball, volleyball, and other jumping sports) and rehabilitation, either on a self-directed program or with a physical therapist. Rehabilitation consists of muscle strengthening, Achilles stretching, and balance training.

Surgical Treatment

Based on your symptoms and your surgeon’s findings from the exam, surgery may be recommended. Surgery usually consists of either a procedure to tighten the existing ligaments or one that uses a separate tendon graft to reconstruct the ligaments. If you have a high arch [cavovarus deformity], your surgeon may also recommend realigning the foot with additional procedures to decrease the risk of instability coming back after surgery. Ankle ligament reconstructions generally have a high success rate.

Video: Ankle Instability

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