Syndesmosis sprains : The high ankle injury

You may have heard various athletes suffering a high ankle sprain or injuring their syndesmosis. But what exactly is a syndesmosis injury? And how does it differ to a normal lateral ankle sprain?

The ankle syndesmosis is the joint between the distal (lowest aspect) of your tibia and fibula. It is comprised by three main supporting ligamentous structures – The anterior inferior tibiofibular ligament, posterior inferior tibiofibular ligament, and interosseous membrane (see Figure 1).  The role of the syndesmosis is to provide stability to the tibia and fibula and resist separation of these two bones during weightbearing tasks. It also plays a role in assisting with mobility of the ankle.

Figure 1: Syndesmosis anatomy

How does it differ to a common ankle sprain?

Generally, a lateral ankle sprain is a result of and inversion injury and will result in an injury to the outside ligaments of your ankle (ATFL, CFL, PTFL). These ligaments are positioned slightly lower than the syndesmosis and provide stability to the true ankle joint.

Figure 2: Inversion sprain mechanism

Mechanisms of injury:

The most common mechanism for injuring your syndesmosis is a forced dorsiflexion combined with an Eversion movement. Essentially the foot/ankle moves in an upward direction and to the outside of the leg (See figure 3).

Figure 3: Syndesmosis Mechanism - Dorsiflexion + Eversion

The syndesmosis can also be injured with a typical inversion or lateral ankle sprain (Figure 2) mechanism. This usually occurs when the incident is of high force and will result with an injury to the lateral ligaments as well.

Signs and symptoms:

·       Mechanism of injury consistent with a syndesmosis injury (forced dorsiflexion + Eversion)

·       Pain location may extend above the ankle and into the lower shin

·       Swelling may sit slightly above the cease line of the ankle joint

·       Difficulty weightbearing, particularly when the foot is in dorsiflexion (knee over toe)

·       Low confidence/feeling of instability

Gradings:

• Grade 1: isolated injury to the AITFL

• Grade 2: Injury to the AITFL and interosseous membrane

• Grade 3: Injury to the AITFL, interosseous membrane and PITFL

• Grade 4: Injury to the AITFL, interosseous membrane, PITFL and deltoid ligament

Immediate management:

As always if you have recently suffered an injury, please seek medical attention from your physio or doctor for accurate diagnosis and management.

If a syndesmosis injury is suspected acute management will initially involve offloading and protecting the tissues. This may be in the form of one or a combination of crutches, a cam walker (moon) boot and strapping.

Your physio or Doctor may also refer you for imaging such as an x-ray or MRI to assist with diagnosis and understanding the severity of the injury.

Following the acute period of offloading and protection a period of rehabilitation will be required to restore normal function of the foot and ankle. In more severe cases surgery may be required to stabilise the syndesmosis and therefore rehab will commence following a period of protection post-surgery.

If you have experienced an ankle sprain yourself, please book in with one of our physiotherapists for an individualised rehabiltation program.