Ankle instability is a condition characterised by the ankle ‘giving way’ or feeling wobbly and unreliable, particularly on uneven surfaces.
There are two main ligaments that support the ankle. The outer ligaments, known as the lateral ligaments, have three components which stop the ankle from rolling and sliding forward. These ligaments are attached to the fibula (small bone next to the shin bone) and the talus (the ankle bone) and calcaneus (heel bone).
An ankle sprain stretches and tears these ligaments and if the sprain doesn’t heal properly, ankle instability can develop.
Symptoms of Chronic Ankle Instability
The “giving way” takes place on the lateral, or outer side and will often occur during sports and walking. However, it can also happen while standing and may be accompanied by swelling, discomfort, tenderness and pain.
Causes of Chronic Ankle Instability
If your ankle feels unreliable and gives way repeatedly, or if you have recurring ankle sprains, it is recommended that you have a full assessment by a foot and ankle surgeon.
Your foot will be examined for signs of swelling and tenderness. By stretching your ankle in different directions, the surgeon will be able to see whether the ligaments are abnormally weak. This is known as a stress view.
The surgeon may take x-rays to check whether there is any damage to the ankle bones. An MRI scan may also be taken.
Diagnosis of Chronic Ankle Instability
Unfortunately, the condition is often misdiagnosed as a sprain. However, an experienced foot and ankle specialist will make a diagnosis on the basis of symptoms, the history of the injury and an examination.
The doctor may observe you as you walk and assess whether you can stand on tiptoe. A method known as the ‘Thompson’s test’ (also known as the ‘calf squeeze test’) may be used. In this test, you will be asked to lie face down on the examination bench and to bend your knee. The doctor will gently squeeze the calf muscles at the back of your leg, and observe how the ankle moves. If the Achilles tendon is functional, the calf squeeze will make the foot point briefly away from the leg (a movement called ‘plantar flexion’). This is quite an accurate test for Achilles tendon rupture.
If the diagnosis is uncertain, an ultrasound or MRI scan may be used.
Chronic Ankle Instability Treatment
Treatment depends upon the severity of the ankle instability and the patient’s own activity levels.
Physiotherapy should be tried as the first treatment and is effective for many patients. Physiotherapy is based on retraining the damaged proprioceptive nerves, enabling them to respond to the movements of the ankle. The strength of muscles around the ankle will also be increased by exercises and activities. If your foot shape makes you prone to extra stress on the ankle ligaments, a moulded insole may be advised for your shoe to reduce these stresses.
Surgery may be considered if ankle instability fails to improve following non-surgical treatment, and depending on the degree of weakness in the ligaments. There are two main types of operation for ankle instability:
The damaged ligaments may be tightened and re-attached to the bone. Known as the Brostrum’s procedure, this type of operation is highly successful and is appropriate for people with active lifestyles.
If all other options have been tried and are neither successful nor suitable, a tenodesis procedure may be carried out. This involves taking a strip of hamstring to recreate new ligaments. This approach should only be considered as a last resort, when the instability is severe and there is likely to be a great deal of stress on the ankle. This type of repair is a very durable treatment for ankle instability but frequently causes stiffness in the ankle.