Anatomy and Function

The ankle works in a systematic way. Movement is only supposed to be in one plane, in other words, up and down. We call this dorsiflexion and plantarflexion. The ankle joint is held in place securely by a group of bones that house the main anklebone (called the talus) inside a box-like effect. On the inside is the medial malleolus and on the outside the fibula.

The inward and outward movements of the back of the foot do not actually occur in the ankle joint but occur in the joint underneath it called the subtalar joint. The muscle that pulls the foot inward (inversion) is slightly stronger than the muscles that pull the foot outward (eversion). When the foot lands in an awkward manner there is a tendency for the heel to roll inwards and create stress on the outside ligaments. If this stress is severe then a sprain of the ankle occurs. A sprain is actually a tear that occurs in the outer supportive ligaments of the ankle. As these ligaments are stretched, a critical point is reached beyond which ligaments do not return to their normal elastic function and a tear of the ligament occurs. Sprains can range from the relatively minor to those where the ligaments are completely torn and the ankle can be quite loose.

The acute sprain of the ankle is commonly associated with marked swelling and bruising on the outer side of the ankle. Rest of the ankle with immobilization of some sort is critical. The classic treatment for a sprain of the ankle is what we refer to as the Rice Program. It involves rest, ice, compression and elevation. This treatment is designed to decrease the inflammation and swelling of the ankle associated with the sprain. The Rice Program by itself will not heal the ligaments. In order for the ligaments to heal the ankle needs to be immobilized with either a cast or a boot. For minor sprains a brace can be applied to the ankle. Walking is permitted during this recovery process, allowing the ankle ligaments to heal.

Following this period of initial immobilization, strengthening exercises are essential to regain the balance of the ankle. It is critical that the tendons and muscles on the outside of the ankle (the peroneal tendons) are strengthened. This should be done initially in a supervised exercise program. If the ligaments have been severely torn, the ability to fine tune the ankle and prevent further sprains from occurring depends on the strength of the peroneal muscles. As the ankle turns repeatedly, the peroneal muscles weaken further. This weakens the ability to prevent recurring sprains. Patients with a high arch or a heel that is naturally turned in slightly are predisposed to sprains.

As a result of continued rolling, turning or instability of the ankle, the ability to fine tune the foot on uneven surfaces becomes limited. The ability to make rapid changes in the position of the foot on the ground surface is called proprioception. If this ability is diminished, the likelihood of a more severe ankle sprain occurring is increased. In recurring ankle sprains we call this chronic recurrent instability of the ankle. The ankle is at risk of developing other problems. These include bruising of the cartilage of the talus and bone spurs that develop around the front and sides of the ankle. These are all precursors of ultimate arthritis of the ankle.

These pictures illustrate a patient with chronic ankle instability. Note how loose the ankle is when it is turned slightly inwards. The ligaments are completely torn in this ankle and the likelihood of recurring sprains is very high.

The diagnosis of chronic recurrent instability is made through a careful examination of the ankle and X-rays that are taken while stress is applied to the ankle.

Here are two X-ray's of a patient with chronic recurrent instability of the ankle. In both the right and the left ankle, an assistant is pushing on the outside of the foot (in the direction of the white arrow) while the XR is taken. The XR on the left is normal, while the one on the right demonstrates a loose (unstable) ankle.