Ankle Sprain and Instability


What is an ankle sprain?

Ankle sprains are an injuries to the ligaments and soft tissue structures that support the ankle joint. They are among the most common orthopedic injuries to the body. These injuries can vary significantly in terms of severity. Almost everyone has tweaked their ankle at some point; typically you shake it out a bit and move on, or perhaps it bothers you for a day or two and then improves.  On the other hand, a person can land with all of their weight on the turned in ankle and be unable to walk for several weeks.  Ankle sprains represent a spectrum of injuries, from the minor to severe.

What causes ankle sprains and instability?

Diagram of ankle sprain mechanics
A twisting force to the lower leg or foot can cause a sprain. The lateral ligaments on the outside of the ankle are injured most frequently. Image courtesy of AAOS.

What is often disrupted when the ankle is sprained is the normal reflex arc that allows for full stability of the ankle. Stretching of the ligament normally causes the muscles on the outside of the ankle to fire, or contract, counteracting the roll onto the outside of the foot.  This reflex is disrupted when numerous ankle sprains occur, leading to continued pain or feelings of instability or both.  Swelling is a common feature of these injuries, and bruising can occur acutely.

How are ankle sprains and instability treated?

The initial treatment of these injuries often involves a period of protection of the ankle in a walking boot.  Casts, splints, and non-weight-bearing treatments can actually delay healing. Once the initial injury has subsided, and the pain and swelling have dissipated to some degree, physical therapy is initiated with a focus on balance and strengthening of the ankle.  Physical therapy is often remarkably successful in this setting, as most patients recover completely without the need for any additional treatment.

How are more serious injuries treated?

In the relatively small proportion of patients that do not improve with physical therapy, an MRI is warranted to assess the status of the ligaments, and to assess the status of the ankle and hindfoot joints and the tendons, especially on the outside of the ankle. Any of these structures can be injured with an ankle sprain, and they are all reviewed on the MRI to assess for injury.  Surgery may ultimately be needed in those patients who do not improve.  Surgery involves tightening up the ligaments on the outside of the ankle.  An ankle arthroscopy is done at the same time to assess the joint and clean up any inflamed tissues.  The tendons about the outside of the ankle will be assessed as well, as all of these structures can contribute to the symptoms.  Good results are an expectation after this surgery, as well as a return to full function once a patient is fully rehabilitated after surgery.