Acute Ankle Sprain

Article Author:
Scott Melanson
Article Editor:
Victoria Shuman
Updated:
9/8/2018 10:14:59 PM
PubMed Link:
Acute Ankle Sprain

Introduction

Acute ankle sprains are commonly seen in both primary care practices and emergency departments and can result in significant short-term morbidity, recurrent injuries, and functional instability. Appropriate initial evaluation and treatment can increase the likelihood of these complications.

Etiology

Ankle sprains occur when there are stretching or microscopic tears of the ankle ligaments due to overstressing those ligaments. This mechanism may also lead to complete tendon disruptions and fractures of the ankle and foot.

Epidemiology

Females and individuals who participate in court and team sports are more prone to ankle sprains. Ankle sprains may also increase the risk of subsequent ankle injuries.

Pathophysiology

The ankle joint is composed of the articulation of the tibia, fibula, and talus. The joint is stabilized by three ligamentous systems: the lateral ligament complex, the medial deltoid ligament, and the syndesmotic ligaments. The most common ankle injury occurs with inversion of the ankle and stressing the lateral ligament complex. The three ligaments that compose this complex are the anterior talofibular (ATFL), the calcaneofibular (CFL), and posterior talofibular (PTFL) and they tend to be injured in this order with the anterior talofibular ligament being injured most commonly. The ATFL is the weakest ligament of the lateral ligament complex, and approximately 70% of lateral ankle sprains involve only this ligament. The posterior talofibular ligament is injured uncommonly.

The medial deltoid ligament is the strongest of the ankle ligaments and tends to be injured with eversion injuries. The distal tibiofibular syndesmotic ligaments bind the tibia and fibula together, and injuries to this complex have been referred to as “high ankle sprains” and are much less common than other sprains. Given the amount of force required to injure this ligamentous complex, these injuries are distinctly uncommon in the general population and tend to occur primarily in competitive athletes. The most common mechanism of high ankle injuries is external rotation and/or ankle dorsiflexion.

History and Physical

In the evaluation of an ankle injury, a practitioner should elicit a history of the mechanism of injury. The practitioner should also investigate whether the injury involved inversion, eversion, rotational stressing, or direct contact, and take into account a history of previous ankle injuries and the patient's ability to bear weight after the injury.

Physical examination should include inspection, palpation, and functional testing. Each of the three lateral ligaments should be palpated at the anterior (ATFL), inferior (CFL), and posterior (PTFL) aspects of the lateral malleoli. The medial ankle should also be palpated along with the entire fibula. A severe ankle injury, typically involving eversion of the ankle, which disrupts the syndesmosis and fracture of the proximal fibula (Maisonneuve fracture). The foot should also be palpated for associated injuries, particularly over the base of the fifth metatarsal and over the navicular bone (proximal medial foot).

Evidence of a syndesmotic sprain can be elicited with the squeeze test and the external rotation stress test. A positive squeeze test results in pain in the area of the tibiofibular syndesmosis when the mid-calf is compressed and released. To perform the external rotation stress test, externally rotate the dorsiflexed foot. Pain with this maneuver is a positive result and suggests a syndesmotic sprain.

Stability of the ATFL can be assessed with the anterior drawer test. This is performed by stabilizing the distal leg with one hand while the other hands grasp the calcaneus. With the foot in 20 degrees of plantar flexion, the examiner pulls forward on the calcaneus. Greater than 1 cm of translation of the foot compared with the uninjured leg suggests ligamentous laxity.

The talar tilt test also assesses the lateral ankle ligaments for laxity, specifically calcaneofibular ligamentous laxity. The test is performed by stabilizing the distal leg in a neutral position while the examiner inverts the ankle. The degree of inversion is compared with the uninjured ankle. Both the talar tilt test and anterior drawer test can be falsely negative soon after the injury due to pain and muscle spasm.

Evaluation

The Ottawa ankle rules have been demonstrated to be accurate in predicting which patients with ankle injuries require x-rays to exclude fractures in both adult and children older than five years.

The Ottawa ankle rules suggest ankle radiographs should be obtained in the setting of pain in the malleolar region and any of the following:

  • Tenderness over the posterior edge of the distal 6 cm or tip of the lateral malleolus
  • Tenderness over the posterior edge of the distal 6 cm or tip of the medial malleolus
  •  Inability to bear weight immediately after the injury and for four steps at the time of evaluation.

A foot series is indicated in patients with midfoot pain and any of the following: 

  • Tenderness of the base of the fifth metatarsal
  • Tenderness over the navicular bone
  • Inability to bear weight immediately after the injury and for four steps at the time of evaluation

These rules should not be used in the presence of a distracting injury, intoxication, conditions causing diminished lower extremity sensation, and those with head injury or other conditions that would make cooperation difficult. The Ottawa ankle rules have been found to have only moderate specificity but a high sensitivity for ankle fractures. Less than 2% of those in whom no imaging was recommended by these rules have been found to have a fracture.

A typical ankle x-ray series would include anteroposterior, lateral, and mortise views. Standard views with a foot series include anteroposterior, lateral, and oblique views.

Treatment / Management

Initial management of ankle sprains includes the PRICE protocol (protection, rest, ice, compression, and elevation). Resting the injured ankle for the first 72 hours followed by gradual resumption of activity as tolerated is a reasonable approach. Initially, crutches can be used, if needed for comfort. When compared with immobilization, early weight bearing with support (elastic bandage or another source of external support) has been found to improve return to sports, return to work, persistent swelling, the range of motion, and patient satisfaction.

Compression can be achieved with an elastic bandage, any lace-up ankle support, or a semi-rigid or inflatable brace. Elevation of the injured ankle above the level of the heart as frequently as possible for the first 24 to 48 hours may lessen the swelling associated with the injury. The range of motion exercises can be initiated when pain and edema resolve. Nonsteroidal anti-inflammatory drugs or acetaminophen can be used for analgesia.

Patients with evidence of ligamentous laxity should be immobilized, given crutches to allow ambulation without weight-bearing of the injured ankle, and referred to a sports medicine specialist or orthopedic surgeon. Patients suspected of having syndesmotic complex strains should also be referred given that these injuries are often associated with a prolonged recovery.

Mild to moderate ankle sprains typically have a full recovery in 7 to 15 days. Symptoms persisting beyond this period should prompt reevaluation. All symptoms should be resolved before return to sports. For highly competitive athletes, reevaluation by a sports medicine physician for all but mild sprains is reasonable before returning to play to ensure full recovery to avoid recurrent injury and ankle instability.

Pearls and Other Issues

An important injury that can be mistaken for an ankle sprain is the Maisonneuve fracture. This injury typically occurs with an eversion injury that results in a tear of the deltoid ligament or medial malleolar fracture. The forced eversion causes a complete disruption of the tibiofibular syndesmosis and fracture of the proximal fibula. This injury, therefore, involves the complete disruption of the ligamentous stability of the ankle thus necessitating surgical fixation. In the absence of a medial malleolar fracture, the associated disruption of the ankle mortise may not be evident on the x-ray and ankle films may be completely normal. Weight-bearing views of the injured foot should demonstrate a widened ankle mortise but often are not obtained unless a high index of suspicion is maintained. Tenderness of the proximal calf should also raise suspicion of this injury. When suspected, x-rays of the tibia and fibula should be obtained.