eMedicine Specialties > Orthopedic Surgery > Foot & Ankle

Acute Ankle Sprains

Author: Ray Foster, MD, FACS, Medical Staff Physician, Black Hills Health and Education Center
Contributor Information and Disclosures

Updated: Apr 30, 2009

Introduction

Ankle sprains are the most common sports injuries encountered today. These injuries occur frequently. Complications such as prolonged ankle pain, a high recurrence rate, and chronic ankle laxity underline the importance of careful diagnosis and treatment of ankle sprains.^1,2

History of the Procedure

In the spring of 1862 at the Royal College of Surgeons, John Hilton gave a series of lectures in which he described performing anatomic studies on an ankle sprain in order to increase his knowledge of the condition.³ Since its development, radiography has been used to study ankle sprains. Radiography is still the first-line investigation of ankle sprains, second only to the classic clinical history and physical examination, since radiographs make it possible to distinguish between ligamentous and bony injuries around the ankle. Currently, magnetic resonance imaging (MRI) allows cartilage and ligament injuries to be diagnosed in ankle injuries.

Problem

Ankle sprains result from force around the ankle that exceeds the tensile limits of the supportive ligaments of the ankle mortise but is less than that which would break the ankle bones. The ankle joint is the site of concentrated forces because it is the dynamic link between the leg above and the foot planted on the earth below.

The large muscle masses of the lower extremity and the momentum of the body’s weight are concentrated on the ankle, connected to the foot, which may be firmly planted on the ground. These factors make ankle sprains the second most frequently encountered outpatient orthopedic condition in many orthopedic clinics (after chronic back pain).

Frequency

Most ankle sprains are probably self-treated and are never reported to a health care provider; therefore, many ankle sprains are not documented. Sprained ankles have been estimated to constitute approximately 15% of all sports-related injuries (see the Rothman Institute site). More than 23,000 people per day, including athletes and nonathletes, require medical care for ankle sprains in the United States.⁴ Stated another way, incident cases have been estimated at 1 per 10,000 persons per day.⁴

Etiology

Mechanical forces exceeding the tensile limits of the ankle joint capsule and supportive ligaments cause ankle sprains. There are a number of contributing factors, which can be classified as predisposing and provocative factors:

• Predisposing factors can include poor muscle tone or proprioceptive sense and shortened and/or contracted joint capsule or tendons from a lack of conditioning. Inadequate training or experience with a physical activity being performed can also predispose to injury.
• Provocative factors include accidents and other unforeseen circumstances that result in mechanical stresses that exceed the tensile limits of the ankle joint capsule and ligaments. Obesity can contribute to sprains by increasing kinetic energy to the point that it exceeds joint-design stress limits.

Pathophysiology

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. It also attaches to the sustentaculum tali of the talus in the center portion; anteriorly, it joins the spring ligament attaching to the tuberosity of the navicular. The deep component of the deltoid ligament is short and attaches to the neck, body, and posterior portion of the talus. The greatest mechanical forces across the ankle joint are directed medially in the normal external rotation of the foot in walking and running. This is reflected in the strength and thickness of the deltoid ligament. The medial malleolus usually fractures before the deltoid ligament fails mechanically.

The anterior and posterior capsular ankle ligaments are relatively thin compared wirh the medial and lateral ankle ligaments. The lateral ankle ligaments are the anterior talofibular ligament, the fibulocalcaneal ligament, and the posterior talofibular ligament. Their attachments and positions are designated by their names.

The ankle joint is a hinged synovial joint with primarily up-and-down movement (plantarflexion and dorsiflexion). The other joints around the ankle are responsible for other movements, giving the ankle a total range of motion comparable to that of a ball and socket. The combined movement in the dorsiflexion and plantarflexion directions is greater than 100°; bone-on-bone abutment beyond this range protects the anterior and posterior ankle capsular ligaments from injury. 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.

The lateral ligament of the ankle joint commonly experiences ankle sprains. The lateral ankle ligament has 3 divisions that run from the lateral malleolus to the surrounding bones. The anterior talofibular ligament is most often injured; this ligament runs from the front of the lateral malleolus to the anterolateral aspect of the talus. The foot is not designed to withstand inversion strains because that is not the position in which it normally functions. When the ankle is stressed in this position, ankle sprain of the anterior talofibular ligament commonly results.

The middle portion of the lateral ankle ligament is called the fibulocalcaneal ligament. It is cordlike and is thicker and stronger than the anterior talofibular ligament. The fibulocalcaneal ligament runs from the tip of the lateral malleolus to the lateral aspect of the calcaneus directly below the fibula. The posterior portion of the lateral ankle ligament is the strongest of the 3 portions of the lateral ankle ligaments and is called the posterior talofibular ligament. It runs almost horizontally from the fossa in the inner aspect of the tip of the lateral malleolus to the posterior tubercle of the talus.

A fifth ankle ligament is rarely sprained because of its great strength. It is a strong, syndesmotic ligament with a deep portion between the bones and superficial, anterior, and posterior portions. 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 tear of this ligament requires surgical treatment. Severe posttraumatic arthritis of the tibiotalar joint (ankle) can result quickly if the tear of the distal tibiofibular ligament syndesmosis remains unrecognized and untreated. Tear of this syndesmotic ligament 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.

Presentation

A history, a physical examination, and radiographs are the only investigations typically indicated in an ankle sprain. Many osteochondral lesions heal with standard ankle sprain care.^5,6,7,8

The history of an ankle sprain is usually of an inversion-type twist of the foot followed by pain and swelling. An individual with an ankle sprain can almost always walk on the foot carefully with pain. The ability to walk on the foot usually excludes a fracture and indicates that a sprain has been experienced in an individual with normal local sensation and cerebral function. A person with a third-degree ankle sprain often reports a history of an audible snap followed by pain and swelling.

The physical examination confirms the diagnosis made on the basis of patient history and differentiates an ankle sprain from a fracture. A sprain is usually well defined by pain over the ligament that is sprained. Ankle motion is painful, and the ankle appears to be in the normal anatomic position. The skin is usually intact with local swelling and bruising in third-degree ankle sprains. A finding of a positive anterior drawer sign in the injured ankle is evidence of an anterior talofibular ankle ligament rupture. The degree of swelling or ecchymosis is proportional to the likelihood of fracture.

The drawer sign is best elicited with 2 hands, with the patient sitting so that the weight of the foot distracts the ankle joint to its normal degree. With 1 hand cupped over the heel and the other hand providing counter pressure over the front of the tibia at the level of the ankle, carefully assess the degree of movement. Repeat these steps for the other ankle, and compare results. In a person with lax joints, several millimeters of bilateral movement  is a negative ankle drawer sign finding. A positive ankle drawer sign finding is a difference of movements in a relaxed patient between the injured side and the uninjured side, with the injured side having more movement than the uninjured.

Women often have more tibial varus than men because the pelvis is wider in females. When this increased tibia varus is associated with an increased calcaneal eversion range of motion, these women are at a greater risk for ankle ligament trauma. Men with an increased talar tilt are at a greater risk for an ankle sprain.⁹

A radiograph is the study of choice to determine if the ankle or foot is fractured.

Indications

The indications for surgery are limited in patients with sprained ankles. One of the few absolute indications for surgery is a distal talofibular ligament third-degree sprain that causes widening of the ankle mortise (please see the Staging section under Workup). To restore the ankle mortise, the distal tibiofibular articulation must be screwed together. The usual postoperative course entails avoiding weight bearing for 6 weeks, followed by removal of the screw, and then continuing external immobilization while allowing weight bearing for an additional 6 weeks. This program serves to avoid breakage of the syndesmotic screw and the associated difficulties that may present.

An isolated complete medial ankle sprain with a palpable defect and demonstrable clinical instability is an indication for surgery, particularly if the deltoid ligament is caught in the medial ankle joint. Surgery allows removal of the ligament from the joint and repair of the ligament.

Evans reported the outcome of 100 randomly selected patients with isolated lateral ligament sprains 2 years after injury. Patients were divided into 2 groups, each with 30 individuals with anterior ligament sprains only and 20 individuals with both anterior and middle ligament ruptures. One group of 50 patients was treated surgically, and the other group was treated with cast immobilization. This study demonstrated no functional or symptomatic advantage for those who were treated surgically. The nonsurgically treated group returned to work earlier and had less morbidity than the surgically treated group of patients.¹⁰

Staples reported that young, active, athletic patients with tears of both anterior talofibular ligaments and calcaneofibular ligaments are best treated surgically. He reported on a group of young athletic patients with only 58% satisfactory results after immobilization, and he subsequently reported on a similar group of patients who had 88.9% satisfactory results with surgical repair.^11,12

The average age of the young, athletic patients that Staples reported on was 19.7 years. In the group of patients who underwent surgery, the average hospital stay was 7.6 days. Six of the 27 patients who underwent surgery had complications (22.2%). Marginal necrosis of the skin at the wound edge and hypesthesia of the 4th and 5th toes and adjacent forepart of the foot were the only reported complications. In selected young patients with high athletic demands who have both anterior talofibular and fibulocalcaneal complete ruptures, surgical repair may be the treatment of choice. In Staples' discussion, the group who underwent surgery had more careful postoperative supervision than the group who underwent immoblilzation treatment alone. Five out of 8 (62.5%) of the patients with double lateral ligament complete rupture, demonstrated by arthrograms, who had refused surgical treatment were completely asymptomatic at 1 or more years after injury.¹²

The cause of continued symptoms after ankle sprain, regardless of the method of treatment, is incompletely understood. Equal supervision of the postinjury course may tend to lessen the difference in outcomes between the surgical and conservative treatment protocols. Newer methods of bracing, such as a controlled ankle motion (CAM) walker and air cast type braces, protect well while allowing mobility and may provide better outcomes than rigid casting. Further research is needed to determine the best treatment for complete double ligament lateral ankle sprains.

Relevant Anatomy

See Pathophysiology.

Contraindications

Currently, it is generally accepted that for most patients, operative repair of third-degree anterior talofibular ligament tears and medial ankle ligament tears does not contribute to an improved outcome. Early active treatment with good follow-up care obviates the necessity for late reconstruction of lateral ankle ligaments for chronic symptomatic instability. See Pathophysiology for the details of the anatomic considerations that make surgery unnecessary (except in cases of distal tibiofibular syndesmosis, as discussed in Indications).

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