A sprain is a stretching, partial or complete tear of a ligament. In the ankle, this can be divided into high ankle sprains involving the syndesmosis and low ankle sprains involving the lateral collateral ligaments.


Low ankle sprains

The bony components of the ankle joint include the distal tibia and fibula and the superior aspect of the talus. Their configuration is such that they form a mortise, with the body of the talus acting as the tenon. This arrangement is secured by a number of ligamentous structures:

• The syndesmosis binds the distal tibia and fibula together (another example of a syndesmosis is the distal radio-ulnar joint). It is composed of the anterior inferior tibiofibular ligament (AITFL), posterior inferior tibiofibular ligament (PITFL), interosseous ligament (IOL) and the interosseous membrane.
• The distal fibular is secured to the to the talus by the anterior and posterior talofibular ligaments (ATFL and PTFL) and to the calcaneus by the calcaneofibular ligament. These ligaments are sometimes referred to collectively as the lateral collateral ligaments.
• The distal tibia is secured to the talus by the deltoid ligament, in view of its triangular shape.

Low ankle sprains

Presentation:

• most common (>90%) with injury to the ATFL the most common offender
• inversion injury most common mechanism
• pain, swelling, tenderness over affected ligaments and sometimes bruising
• patients usually able to weight bear unless severe
• they can be classified as follows

High ankle sprains

Presentation:

• Injuries to the syndesmosis are rare (about 0.5%) and severe.
• The mechanism of injury is usually external rotation of the foot causing the talus to push the fibula laterally.
• Patients frequently find weight-bearing painful in comparison to low ankle sprains.
• Pain when the tibia and fibula are squeezed together at the level of the mid-calf (Hopkin’s squeeze test).

Low ankle sprains

Investigation:

• Radiographs should be done according to the Ottawa ankle rules as 15% of sprains are associated with a fracture.
• MRI if persistent pain and useful for evaluating perineal tendons.


High ankle sprains


Investigations:

• Radiographs may show widening of the tibiofibular joint (diastasis) or ankle mortise.
• MRI if high suspicion of syndesmotic injury, but normal plain films.

Low ankle sprains

Treatment:

• Non-operative with rest, ice, compression and elevation (the so-called RICE protocol).
• Occasionally a removable orthosis, cast and/or crutches may be required for short-term symptom relief.
• If symptoms fail to settle or there is significant joint instability then an MRI and surgical intervention may be contemplated, but this is rare.

High ankle sprains


Treatment:

• If no diastasis then non-weight-bearing orthosis or cast until pain subsides.
• If diastasis or failed non-operative management then operative fixation is usually warranted.

Isolated injuries to the deltoid ligament are rare as they are frequently associated with a fracture and one should always be on the lookout for Maisonneuve fracture of the proximal fibula. Provided the ankle mortise is anatomically reduced then treatment can be as per a low ankle sprain, if not then reduction and fixation may be warranted.