Essentially, the ankle consists of three bones, the tibia, fibula and talus, all held together by thick fibrous ligaments. The bottom parts of the tibia and fibula (shin bones) join together and surround the talus in such a way that it is able to rock forwards and back while providing stability and restricting the side-to-side movements.
The ligaments holding the tibia and fibula together are large and thick, forming a syndesmosis. An injury to this area is known as a high ankle sprain.
How do they happen?
A high ankle sprain can occur when your lower leg twists inwards while your foot is planted on the ground. The foot is typically pushed back and rotated outwards, putting excess pressure on the ligaments that hold the lower leg bones (tibia and fibula) together. This force can cause the syndesmosis to tear resulting in a gapping of the two bones, which can lead to significant instability of the ankle. This can happen simply from a fall, but more commonly while playing sports that involve running and jumping. This is also a common injury for downhill skiers. You are often unable to walk on your toes after this type of injury.
What is the difference between a high and a low ankle sprain?
A "normal" or low ankle sprain is a tear of the ligaments connecting the ankle to the foot, a syndesmosis tear (between the bottom of the tibia and fibula) is called a “high” ankle sprain. High ankle sprains are much less common than lower ankle sprains, accounting for only 1-11% of all ankle injuries. It can initially be difficult to tell the two injuries apart. To complicate things, a fracture of the ankle will also have similar symptoms. Your physiotherapist has a set of physical tests they can perform if they suspect a high ankle sprain. Ultimately imaging such as X-Rays or an MRI may be required to confirm the diagnosis.
Why does correct diagnosis matter?
High ankle sprains can take up to two times longer to heal than normal ankle sprains and require more immediate attention. Syndesmosis tears that are left untreated can result in chronic instability and pain, making them vulnerable to further injury in the future. Furthermore, if the separation of the tibia and fibula is severe enough, early surgery to fixate the injury with a screw or a "tightrope" to pull them back together may be required.
What is the treatment?
As mentioned, severe and unstable tears may require surgery, but most syndesmosis tears will need to be put into a supportive boot for around 4-6 weeks. Following this period a graduated rehabilitation program of strengthening, mobilization, balance, control and agility will need to be commenced before your ankle will be back to its pre-injury level of function. This can take up to 6 months in some cases.