What is the pathophysiology of ankle sprain?

Updated: Jan 14, 2019
  • Author: Craig C Young, MD; Chief Editor: Sherwin SW Ho, MD  more...
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The lateral ankle complex, which is composed of the anterior talofibular, calcaneofibular, and posterior talofibular ligaments, is the most commonly injured site. [1, 2, 3, 4] Approximately 85% of such sprains are inversion sprains of the lateral ligaments, 5% are eversion sprains of the deltoid or medial ligament, and 10% are syndesmotic injuries. The ATFL is the most likely component of the lateral ankle complex to be injured in a lateral ankle sprain. Osteochondral or chondral injuries of the talar dome should be considered when diagnosing an ankle injury.

During forced dorsiflexion, the PTFL can rupture. With forced internal rotation, ATFL rupture is followed by injury to the PTFL. Extreme external rotation disrupts the deep deltoid ligament on the medial side, and adduction in neutral and dorsiflexed positions can disrupt the CFL. In plantarflexion, the ATFL can be injured.

The strongest ankle capsule-ligament complex is the deltoid ligament, which has 2 parts: the superficial component and the deep component. The superficial component runs the farthest from the medial malleolus to the medial aspect of the calcaneus, posteriorly. The medial malleolus usually fractures before the deltoid ligament fails mechanically.

Ankle spurs may occur at any of the bony ligament attachments. On lateral radiographs, it is not uncommon to see an anterior spur at the neck of the talus, where the anterior ankle capsule attaches. This is caused by ossification of the hematoma organization associated with anterior ligament sprains.

Because of its great strength, the syndesmotic ligament, which has a deep portion between the bones and superficial, anterior, and posterior portions, is rarely sprained. This distal tibiofibular ligament holds the distal tibia and fibular bones together at the ankle joint and maintains the integrity of the ankle mortise. It takes a great amount of force to strain this ligament, which normally does not have much excursion. A significant tear of this ligament requires surgical treatment. Severe posttraumatic arthritis of the tibiotalar joint (ankle) can result quickly if a syndesmosis tear remains unrecognized and untreated. A syndesmotic ligament tear is usually a part of an ankle fracture that needs to be treated specifically. This is not generally true of the other ankle ligament tears.

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