The unstable ankle or ankle instability What is an unstable ankle?
During weight bearing activity an unstable ankle feels as though it will give way or let you down. It may actually do so. The patient may beable to prevent it once it starts or restrict activities so that it occurs less. What are the causes of ankle instability?
Most commonly this starts after an episode of injury, usually an ankle sprain. The main question is whether the ankle ligaments are lax and the ankle therefore mechanically unstable. This can be diagnosed by comparing how stable the ankle is compared with the normal unsymptomatic side. It is possible that the ligaments may be mechanically normal but the ankle never the less feels unstable to the patient. This is called functional instability because the ankle joint cannot be demonstrated to be unstable by examination. There are various causes for this either originating from inside or outside of the ankle joint. Within the joint inflamed soft tissue resulting from the injury known as synovitis ( LatSynovitis Download movie) or an injury to the joint lining ChondralFlap (1.1MB) Download movie (1.1MB) may lead to pain / reflex spasm in certain positions of the foot. An injury outside the ankle joint to the peroneal tendons, causing them to sublux PeronealPreop (835KB) Download movie (826KB) can also be responsible. Another possible cause is an injury to the 'position-feedback' nerves around the ankle and is probably the diagnosis if the other causes have been excluded. | 
