Chronic ankle instability can be both a cause and a result of an ankle sprain. This condition occurs when an ankle injury—usually an inversion ankle sprain causing injury to the lateral ankle ligaments—stretches, ruptures, or tears.

Subsequently, the ligament fails to heal properly. While most ankle sprains heal without further complications, about 10 percent of them heal in a lengthened, lax state.

This makes the injured ankle less able to support the body’s weight—i.e., less stable—which predisposes the patient to additional sprains and other ankle injuries in the future.

Athletes are especially prone to this condition—particularly ballet dancers, whose ligaments are already looser than normal. Some of the most common predisposing factors to ankle sprains are muscle weakness, a tight Achilles tendon, and a fixed deformity of the forefoot or rearfoot.

What Are The Symptoms of Ankle Instability?

The symptom that defines this condition is instability of the ankle—an inability to firmly put weight on the foot without a constant fear of rolling the ankle.

Often there is also pain, swelling and bruising associated with ankle instability. In most cases the patient who suffers from this condition will walk with a pronounced limp.

Mechanical vs. Functional Ankle Instability

Ankle instability is classified as either “mechanical” or “functional.” Mechanical ankle instability involves an ankle that has clinical hypermobility and lax ligaments; if you suffer from this condition your doctor will be able to objectively measure this instability using clinical tests.

The term functional ankle instability, on the other hand, refers to a subjective condition in which the ankle only feels as though it were unstable.

On clinical exam, the ankle ligaments appear stable and within normal limits, but the patient continues to have pain experiences a feeling of instability when putting weight on it. This condition can be caused by a number of different ankle conditions, such as:

• Osteochondral lesion of the talus—an area of bone and cartilage on the top of the talus that is damaged
• Damage to nerve fibers within the damaged ligaments that help control balance
• Ankle impingement
• Arthritis in the ankle

Mechanical ankle instability is treated differently than functional ankle instability, so it is important that your ankle problem be diagnosed properly. Mechanical instability frequently is treated surgically, while functional instability is typically treated with bracing and physical therapy.

Causes and Complications of Ankle Instability

A lateral ankle sprain occurs when the foot is twisted inward, stretching the ligaments to the point of injury. If this injury is not properly treated by reducing inflammation, and by resting the affected ankle and protecting it from further trauma, it may remain stretched into a lengthened position and subsequently heal that way.

This will increase the risk of chronic ankle instability—predisposing the patient to additional sprains in the future. It can therefore be said that chronic ankle instability is caused by ankle sprains—and in turn that ankle sprains are sometimes caused by chronic ankle instability.

Naturally, each additional sprain worsens the chronic instability.

How is Chronic Ankle Instability Diagnosed?

Diagnosis of chronic ankle instability begins with imaging tests—e.g., x-rays, MRI, CT scans, and sometimes even fluoroscopy (in layman’s terms, a kind of x-ray movie).

In some cases a stress x-ray may be ordered, which involves moving your ankle in certain directions while taking x-rays or fluoroscopic images in order to visualize the instability present.

How is Chronic Ankle Instability Treated?

Treatment of chronic ankle instability will depend on the severity of the problem, but in many cases surgical correction will be required. Conservative treatment will begin with physical therapy. Your doctor may have you wear an ankle brace for a period of time.

If surgery is necessary, however, there are a number of different surgical approaches that may be taken. One is to directly repair the injured ligaments by shortening and tightening the stretched ligaments.

Another option is to replace or augment the damaged ligaments with donor tissue. This donor tissue may be synthetically created or may be harvested from the patient’s own leg and repurposed as an ankle ligament.

Can Chronic Ankle Instability Be Prevented?

As with any health matter, prevention is essential and is often the best treatment. Severe ankle sprains can often be prevented by the use of proper footwear and other protective gear when participating in sports.

If you do sprain your ankle, it is important to treat it properly and cooperate with your doctor by following his or her instructions.

Since ligaments are not directly served by arteries, they depend on what is called microcirculation to obtain oxygen and nutrients.

This poor blood supply means they do not heal as easily as other tissue, which makes it important to encourage circulation by avoiding substances that can constrict this blood supply, such as alcohol, caffeine, and salt.

Compression and immobilization of the affected joint are also important. If an ankle sprain is treated in such a way as to allow it to heal properly, chronic ankle instability can often be avoided.