An ankle that feels loose or weak, and is prone to “giving way”, is defined as being unstable.
Instability is most commonly the result of having torn one or more of the components of the lateral ligament complex (which consists of three parts). However, it can also result from torn or weak peroneal tendons, or malalignment, when the heel is turned in (usually in combination with an overly-high arch).
The lateral ligaments are the static stabilisers of the ankle. The peroneal musculotendinous units are the dynamic stabilisers. To have a truly stable ankle, both components need to be intact and functioning!
The lateral ligaments of the ankle are most-commonly torn during twisting injuries playing sport, stepping on uneven surfaces or falling awkwardly. When an inversion (turning in) episode occurs suddenly under load, and if this is accompanied by a painful popping or snapping sensation, with the rapid onset of swelling over the outside of the ankle, either a fracture or ligament tear is likely to have occurred. Investigations should always include Xrays, but may also involve an MRI or CT examination. These tests usually confirm a suspected diagnosis, but in experienced hands a ligament rupture can be determined clinically ie. on physical examination alone.
Almost all acute ligament tears are managed non-operatively as the prognosis with a good conservative program is typically excellent. Ligament reconstructions are usually preserved for those with chronic (long-standing) instability when there is no chance of non-operative measures being successful.
Loss of peroneal tendon function is most commonly the result of tendinopathy, with degenerative change causing tearing of either one or both of the two tendons. Tears usually run up and down the tendon (longitudinally) and they are accompanied by inflammation (tenosynovitis). Pain often accompanies this problem, leading to dysfunction ie. weakness and loss of the normal reflex response to a twisting load on the ankle.
Lateral ligament and tendon dysfunction often go hand in hand in the chronically unstable ankle, and the presence of one can give rise to the other!
Completely torn (ruptured) peroneal tendons usually need to be either repaired or reconstructed.
Many people are born with a varus (turned-in) heel. However, this pattern of hindfoot deformity can also develop over time as a result of either lateral ligament or peroneal tendon chronic dysfunction. The more severe the varus, the more severe the instability is likely to be. It needs to be addressed at the time of any ligament and/or peroneal tendon reconstruction, and this is usually done by performing a calcaneal osteotomy (an operation involving changing the shape of the heel bone to restore hindfoot alignment).
Long-standing ankle instability and malalignment can lead to the development of pathology affecting the joint surfaces of the ankle (eg. talar dome osteochondral lesions) and osteoarthritis of the ankle and subtalar joints, and these can be part of a vicious cascade or “domino effect” of progressive destructive pathology leading to steadily worsening instability, deformity, pain and swelling. Although all of these issues are manageable, there is often an element of eventual functional compromise and the problems are best avoided in the first place by good early injury treatment.
Learn more about Surgery for Complex Ankle Instability
All surgical procedures involve risks. The information provided here is for general educational purposes only. For specific advice regarding instability of the ankle, please book an appointment with Dr Newman.