Chronic Ankle Instability
What Is Chronic Ankle Instability?
Ankle instability is a result of weakness or laxness in the ligaments that surround the ankle joint (tibial-fibular-talar joint). It is a fairly common condition, especially in people who play high impact sports (basketball, football etc). Usually, ankle instability is a result of sprains injuring the ligaments.
Sprains can also damage other structures in the foot, and these secondary injuries can also contribute to symptoms of instability, pain and stiffness.
Ligaments are bands of tissue similar to tendons (fibrous tissue), and generally attach bone to bone. They act as stabilising structures around the bones that form the joint - similar to the way cables and guy ropes support bridges.
In the ankle there are two primary sets of ligaments that support the joint:
- the triangular medial ligament (aka deltoid ligament), and
- the lateral ligaments (the 3 main lateral ligaments include the anterior and posterior fibulotalar + the fibulo-navicular ligaments).
There is also a subtalar ligamentous complex that is involved in joint stability, but is difficult to describe.
The medial ligament sits on the inside surface of the ankle and is very strong. For this reason it is less likely to be the culprit in ankle instability. Conversely, the lateral ligaments sit on the outside of the ankle and are relatively weak. Consequently they are likely to be involved in instability, and also in sprains (see Ankle Sprain). Although the lateral ligaments sit on the outside of the foot, they prevent the foot from twisting inwards, so lateral chronic ankle instability involves a tendency of the foot to invert, rather the evert.
When ligaments are lax, muscles around the ankle can compensate for their weakness. When the lateral ankle ligaments are lax the 'peroneus' muscles can help support the joint . These muscles are long and thin and sit underneath the large calf muscles (gastrocnemius). They wrap around the outside of your ankle before attaching to the long bone that continues to become the fifth toe (base of the fifth metatarsal).