Chronic ankle instability or 'lateral ligament instability' is a condition in which patients frequently experience the outer part of their ankle 'collapsing', 'giving-way' or 'rolling over' during walking over uneven surfaces.
Chronic instability occurs as a result of weakness of the lateral ligament complex of the ankle due to repeated stretching and tearing injuries (sprains) that fail to adequately heal.
The condition is common among athletes, who often experience ankle sprains as a result of their sport. It can be accompanied by various injuries to the articular cartilage in the ankle that can become damaged during a spraining incident. In addition, the overlying peroneal tendons on the outside of the ankle can become over-worked in an attempt to stabilise an ankle that has a lateral ligament complex deficiency.
Symptoms and Progression
Patients with chronic ankle instability often experience pain or swelling around the affected ankle, frequent 'collapses' of the ankle on standing or walking, as well as a general feeling of instability around the joint.
Repeated sprains further weaken the ligaments of the ankle and compounds the problem. Although the ankle ligaments do heal they often heal lengthened in an ankle with poor neuromuscular feedback or 'proprioception'. This reduces the ankle's ability to guard against repeated injury.
The diagnosis of ankle instability is clinical- based on history and clinical examination findings proving instability. Stress X-rays of the ankle joint are rarely justified. Standing X-rays of the ankle are important to exclude other injuries such as fracture or injury to the lower tibiofibular (syndesmosis) joint. Cross sectional imaging such as MRI is used mainly to exclude a co-existent injury to the articular cartilage in the ankle.
Isolated, single occurrence ankle sprains rarely require surgical reconstruction, as the ligaments heal on their own with adequate rest and immobilisation. An acute ankle sprain benefits from a short period (one to two weeks) of plaster or Air Cast immobilisation. This in theory allows the ligaments to heal to their correct length and tension.
Physiotherapy should always be employed, even in those patients seeking surgery. There is often a tendency for the usual feedback mechanisms that guard against ankle injury to become delayed and for there to be peroneal tendon weakness. This reduced proprioception and balance requires pre-operative optimisation.
Patients may also benefit from wearing an ankle brace to support the joint and guard against further injury.
If the patient is experiencing pain or inflammation, nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen will help to make symptoms more manageable.
With repeated disabling ankle sprains surgery is recommended, especially if non-operative treatment has failed to stabilise the ankle. When there is evidence of injury to the articular cartilage in the ankle joint as a consequence of instability, surgery again may also be indicated.
Surgery involves an arthroscopic assessment (key-hole surgery) of the ankle which permits injury to the cartilage to be treated. At the same operation, the two ligaments forming the lateral ligament complex, the CFL (calcaneofibular ligament) and the ATFL (anterior talofibular ligament) are repaired by direct reattachment to their origin on the fibula with strong stitch-anchors.