Ankle sprain in adults: Evaluation and diagnosis

INTRODUCTION — Ankle injuries are among the most common problems presenting to primary care offices and emergency departments [1-3]. Patients with ankle sprains (stretching, partial rupture, or complete rupture of at least one ligament) constitute a large percentage of these injuries.

The epidemiology, presentation, and evaluation of common ankle sprains are reviewed here. The management of common ankle sprains and the evaluation and management of high ankle sprains (syndesmosis injuries) are discussed separately. (See "Ankle sprain in adults: Management" and "Syndesmotic ankle injury (high ankle sprain)".)

Other injuries of the lower leg, ankle, and foot are covered separately, including the following topics:

●Fractures of ankle and adjacent bones (see "Ankle fractures in adults" and "Talus fractures" and "Fibula fractures" and "Stress fractures of the tibia and fibula" and "Tibial shaft fractures in adults")

●Ankle tendon injuries (see "Achilles tendinopathy and tendon rupture" and "Non-Achilles ankle tendinopathy" and "Calf injuries not involving the Achilles tendon")

●Pediatric ankle injuries (see "Foot and ankle pain in the active child or skeletally immature adolescent: Evaluation" and "Ankle pain in the active child or skeletally immature adolescent: Overview of causes")

●Foot injuries (see "Overview of foot anatomy and biomechanics and assessment of foot pain in adults" and "Evaluation and diagnosis of common causes of hindfoot pain in adults" and "Evaluation, diagnosis, and select management of common causes of midfoot pain in adults")

EPIDEMIOLOGY AND RISK FACTORS — Ankle sprains are among the most frequently managed injuries presenting to emergency departments and primary care clinics. Lateral ankle sprains are most common; most injuries are sustained during sport [3-7]. According to systematic reviews of prospective epidemiology studies, the incidence of ankle sprain is higher among adult females than adult males, and higher among children and adolescents than adults [3]. (See 'Classification of ankle sprains' below.)

Systematic review of the ankle sprain literature has revealed a number of intrinsic and extrinsic risk factors [4]. Intrinsic, or patient-related, risk factors for lateral ankle sprain include limited dorsiflexion, reduced proprioception, and deficiencies in balance. The main extrinsic, or environmental, risk factor appears to be the type of activity, with indoor court sports posing the highest risk [3]. Risk is also relatively high for outdoor court sports. This may be due in part to the increased friction between shoe and playing surface during court sports [8,9]. While evidence is limited, foot and ankle injury rates among field athletes may be higher when playing on artificial turf versus natural grass [10].

Multiple studies show that ankle sprain is the most common injury in organized sport [7,11]. Aeroball, basketball, indoor volleyball, field sports, and climbing had the highest incidence of lateral ankle sprain in one systematic review [4]. Playing soccer on natural grass rather than turf and playing defender increased risk of ankle sprain, as did landing after a jump in volleyball. Modifiable risk factors should be identified and addressed as part of any prevention or rehabilitation program to decrease the risk of recurrent injury. (See "Ankle sprain in adults: Management", section on 'Rehabilitation' and "Ankle sprain in adults: Management", section on 'Prevention'.)

Lateral ankle sprain is the most common sprain sustained during sport, ranging from 70 to 90 percent of all sprains, depending on the demographic [7,11,12]. The anterior talofibular ligament is the only ligament injured in 73 percent of ankle sprains. Acute ankle sprain accounts for 15 to 17 percent of all high school sports injuries.

While not fully representative of participants in all sports, epidemiologic data collected from United States college athletic teams over five academic years provides a good general understanding of lateral ankle sprains [7]. Notable findings include the following:

●2429 lateral ankle sprains were reported, accounting for 7.3 percent of all reported sports-related injuries and an overall rate of 4.95 per 10,000 athlete-exposures

●Lateral ankle sprain occurred most often in men's basketball (11.96 per 10,000 athlete-exposures; 15 percent of total injuries), women's basketball (9.50), women's soccer (8.43), men's soccer (7.43), women's volleyball (6.92), and American football (6.87)

●The majority of ankle sprains occurred during practice, but the injury rate (per hour of participation) was higher in competition

●11.9 percent of lateral ankle sprains were recurrent

CLASSIFICATION OF ANKLE SPRAINS

Location — The mechanism of injury generally determines the location of the sprain (figure 1).

Lateral ankle sprain — The most common mechanism of ankle injury is inversion of the plantarflexed foot (figure 2), which causes damage to the lateral ligament complex of the ankle. This complex consists of the anterior talofibular, calcaneofibular, and posterior talofibular ligaments (figure 3). The three ligaments within this complex are injured in a predictable sequence as forces increase.

The anterior talofibular ligament is the only ligament injured in the majority of ankle sprains. Stronger forces lead to ruptures of both the anterior talofibular and calcaneofibular ligaments, which can result in significant ankle instability. Isolated injury of the calcaneofibular ligament is uncommon, but stronger forces result in injury to all three ligaments. Such injuries, while uncommon, are more debilitating and more commonly associated with significant nerve injury [13].

Medial ankle sprain — The medial deltoid ligament complex (figure 4) is the strongest of the ankle ligaments and is infrequently injured in isolation. More often, it is part of a multi-ligamentous injury, such as a syndesmosis-deltoid injury. (See "Syndesmotic ankle injury (high ankle sprain)".)

Forced eversion of the ankle can cause isolated damage to the deltoid complex, but more typically results in an avulsion fracture of the medial malleolus, due to the strength of the deltoid ligament [14]. In a study of military cadets with ankle sprains, approximately 5 percent involved the deltoid ligament, and two sports (rugby and gymnastics) posed the highest risk [15].

Deltoid ligament sprains may occur as part of a more significant injury involving the lateral ligaments and/or the syndesmosis. In a magnetic resonance imaging (MRI) study of 180 severe ankle sprains seen in the emergency department, 78 had some signal change in the deltoid ligament [16]. In a study of patients with chronic ankle instability requiring surgery, MRI revealed that up to 36 percent had signs of deltoid injury and 42 percent of syndesmosis injury [17].

Syndesmotic sprain (high ankle sprain) — Dorsiflexion and external rotation of the foot relative to the tibia or eversion of the ankle may cause sprain of the syndesmotic structures, which include the anterior tibiofibular, posterior tibiofibular, and transverse tibiofibular ligaments; and the interosseous membrane (figure 5) [18]. These structures are critical to ankle stability. Syndesmotic ligament injuries contribute to chronic ankle instability and are more likely to result in recurrent ankle sprain and heterotopic ossification [19]. Syndesmosis sprains range from 1 to 11 percent of all ankle sprains, with a higher rate among participants in contact sports [20]. Syndesmotic ankle injury is reviewed in detail separately. (See "Syndesmotic ankle injury (high ankle sprain)".)

Grading — Ankle sprains have traditionally been classified based upon clinical signs and functional loss from grade I to grade III:

●A grade I sprain results from mild stretching of a ligament with microscopic tears. Patients have mild swelling and tenderness. There is no joint instability on examination, and the patient is able to bear weight and ambulate with minimal pain. Due to their benign nature, these injuries are not frequently seen in the office.

●A grade II sprain is a more severe injury involving an incomplete tear of a ligament. Patients have moderate pain, swelling, tenderness, and ecchymosis. There is mild to moderate joint instability on exam with some restriction of the range of motion and loss of function. Weightbearing and ambulation are painful.

●A grade III sprain involves a complete tear of a ligament. Patients have severe pain, swelling, tenderness, and ecchymosis. There is significant mechanical instability on exam and significant loss of function and motion. Patients may not be able to bear weight or ambulate.

Although higher-grade sprains involve more severe injuries to ligaments, the time for healing is not always proportional to the grade of the sprain.

CLINICAL EVALUATION

History — Evaluation of an injured ankle requires a careful history. The mechanism and structures damaged with each major type of sprain are described above. (See 'Classification of ankle sprains' above.)

As part of the history, it is important to determine:

●The mechanism of injury – The answer helps to direct the rest of the examination (figure 1).

●Whether or not the patient could walk after the injury – The answer helps to stratify the risk of fracture and whether radiographs are needed.

●Whether the ankle had been previously injured – People with a history of ankle sprains are more likely to reinjure the same ankle; a study in basketball players found repeat ankle injuries almost five times as likely as primary injuries [21].

Physical examination — Physical examination of the ankle includes inspection, palpation, determination of weightbearing ability, and injury-specific physical diagnostic tests.

●Inspection – Look for swelling and ecchymosis.

●Palpation – Palpate the entire fibula (a syndesmotic injury may be associated with a fracture of the proximal fibula [Maisonneuve fracture]), the distal tibia, the foot, and the Achilles tendon. The Thompson test (picture 1 and movie 1) should be performed if any tenderness or a tissue deficit is detected while palpating the Achilles tendon. (See "Achilles tendinopathy and tendon rupture", section on 'Physical examination'.)

Check for tenderness in the areas required for the Ottawa ankle rules (posterior edge or tip of the lateral malleolus, posterior edge or tip of the medial malleolus, base of the fifth metatarsal, navicular bone). (See 'Ottawa ankle rules' below.)

Tenderness of the distal tibia or fibula may represent fracture associated with inversion or eversion injuries. Tenderness over the ligamentous structures is a nonspecific finding but often indicates injury.

An eversion, external rotation, or hyperdorsiflexion injury associated with tenderness at the distal tibiofibular joint (picture 2) without significant swelling suggests a syndesmosis sprain.

Effusion and pain on palpation of the talocrural joint line (picture 3) may suggest a fracture of the osteochondral talar dome resulting from direct trauma between the talus and the fibula or tibia.

●Assessment of inversion-eversion – Check for pain on gentle passive inversion and eversion of the ankle. In lateral ankle sprains, pain is increased with forced ankle inversion, while the pain of a medial (deltoid) ligament sprain is accentuated by eversion of the ankle.

●Special tests – Perform specific examination maneuvers (described below) including the squeeze test, the external rotation stress test, the anterior drawer test, and the talar tilt test. Although these maneuvers can be helpful, they have not been rigorously studied [22].

If there is no swelling or ecchymosis, physical examination maneuvers do not elicit pain, and the Ottawa ankle criteria for imaging are not met (see 'Ottawa ankle rules' below), there is unlikely to be structural damage.

Special tests

Squeeze test — The squeeze test consists of compression of the fibula against the tibia at the mid-calf level. This maneuver elicits pain in the region of the anterior tibiofibular ligament (anterior to the lateral malleolus and proximal to the ankle joint) when a syndesmotic sprain has occurred (picture 4).

External rotation stress test — The external rotation stress test can also help identify a syndesmotic sprain (picture 5). The clinician stabilizes the leg proximal to the ankle joint while grasping the plantar aspect of the foot and rotating the foot externally relative to the tibia. The test is positive if pain is elicited in the region of the anterior tibiofibular ligament (anterior to the lateral malleolus and proximal to the ankle joint).

Anterior drawer test — The anterior drawer test detects excessive anterior displacement of the talus on the tibia. If the anterior talofibular lateral ligament is torn by an inversion stress, the talus will sublux anteriorly and laterally out of the mortise. The test is performed with the patient's foot in the neutral position (slightly plantarflexed and inverted). The lower leg is stabilized by the examiner with one hand, and with the opposite hand, the examiner grasps the heel while the patient's foot rests on the anterior aspect of the examiner's arm. An anterior force is gently but steadily applied to the heel while holding the distal anterior leg fixed (picture 6). The amount of movement should be compared with the uninjured side to determine joint laxity.

The anterior drawer test has limited usefulness in the acute setting because pain, swelling, and muscle spasm may limit mobility of the joint and interfere with the test's reliability. The test is more sensitive and specific when performed between four and five days after an acute ankle sprain and is helpful in the evaluation of chronic ankle instability [4]. (See 'Deferred examination' below.)

Talar tilt test — The talar tilt test detects excessive ankle inversion. If the ligamentous tear extends posteriorly into the calcaneofibular portion of the lateral ligament, the lateral ankle is unstable and talar tilt occurs. With the ankle in the neutral position, a gentle inversion force is applied to the affected ankle, and the degree of inversion is observed and compared with the uninjured side (picture 7). As with the anterior drawer test, this maneuver is of limited usefulness in the acute injury when pain, swelling, and muscle spasm are present; and it may be more important in evaluating chronic ankle instability.

If a medial ankle (deltoid ligament) sprain is suspected, a lateral talar tilt test can be performed. The technique is identical but with a gentle eversion force applied to the affected ankle [14].

Deferred examination — Deferred examination may improve the diagnosis of ligamentous injuries and instability [4]. As an example, a study of 160 consecutive patients with inversion injuries found that performing a physical examination five days after the injury improved the accuracy of diagnosing ligament rupture [23]. The positive predictive value for ligament rupture of the triad of pain on palpation of the anterior talofibular ligament, lateral discoloration due to hematoma, and a positive anterior drawer sign was 95 percent.

Despite this, many patients with acute ankle injuries, particularly grade I sprains, can be appropriately managed and triaged without performing a deferred examination. (See 'Grading' above.)

DIAGNOSTIC IMAGING

Determining the need for radiographs — While not well studied in the primary care setting, it is estimated that fracture of the ankle or midfoot occurs in fewer than 15 percent of patients presenting to an emergency department with an acute ankle sprain [24-28]. The Ottawa ankle rules were developed to reduce the number of unnecessary radiographs in such patients [29]. How to determine whether imaging studies are needed in children and the use of clinical decision rules in such a setting are discussed in detail separately. (See "Ankle fractures in children".)

Ottawa ankle rules — The Ottawa ankle rules were developed, tested, and validated in adult patients presenting to the emergency department with acute ankle injuries. Although their use specifically in the primary care setting has not been assessed, the rules have demonstrated excellent results in both pediatric and adult emergency department patient populations.

Although multiple systematic reviews have found the Ottawa ankle rules to perform extremely well, as with any guidelines, there are specific circumstances when clinical judgement should supersede them. As an example, patients with diminished peripheral sensation, such as diabetics or intoxicated patients, may need radiographs regardless of the Ottawa criteria. Missed fractures are a significant cause for litigation in the United States. The use of decision rules with children is reviewed in detail separately. (See "Foot and ankle pain in the active child or skeletally immature adolescent: Evaluation", section on 'Imaging'.)

The Ottawa ankle rules are as follows (figure 6):

Plain radiographs of the ankle are only indicated for patients who have pain in the malleolar zone and

●Have bone tenderness at the posterior edge or tip of the lateral or medial malleolus

or

●Are unable to bear weight both immediately after the injury and for four steps in the emergency department or doctor's office

Plain radiographs of the foot are only indicated for patients who have pain in the midfoot zone and

●Have bone tenderness at the base of the fifth metatarsal or at the navicular

or

●Are unable to bear weight both immediately after the injury and for four steps in the emergency department or doctor's office

The following apply to the use of the Ottawa ankle rules:

●If the patient can transfer weight twice to each foot (four steps), he or she is considered able to bear weight even if he or she limps

●Palpate the distal 6 cm of the posterior edge of the fibula when assessing for bone tenderness

A systematic review of 27 studies including 15,581 patients found that the Ottawa ankle rules were highly sensitive (96.4 to 99.6 percent) for excluding ankle fracture [30]. Specificity was modest and varied widely (10 to 79 percent), but the rules were purposely calibrated for high sensitivity at the expense of specificity. Fewer than 2 percent of patients who were negative for fracture according to the rules had a fracture. Subsequent reviews have confirmed the high sensitivity and variable specificity of these rules [31]. It has been estimated that use of these rules in the emergency department for patients presenting with an acute ankle sprain would reduce the number of unnecessary radiographs by 30 to 40 percent.

Selection of imaging modality — Malleolar fractures, distal fibula fractures, talar dome fractures, and syndesmosis separation may be diagnosed by plain radiograph. If indicated, anteroposterior, lateral, and mortise (ie, 3 view ankle) radiographs should be obtained (image 1 and image 2 and figure 7). Weight-bearing radiographs may help to identify syndesmosis or deltoid ligament injuries (and associated ankle joint instability requiring surgical consultation), based on findings such as asymmetric ankle joint space on mortise view [32,33]. We prefer weight-bearing radiographs if the patient can stand. (See 'Determining the need for radiographs' above.)

“Classic” stress radiography (obtaining plain radiographs while performing a talar tilt, anterior drawer, or external rotational stress maneuver) is sometimes performed, although it may be painful for patients. [34-37]. Dynamic joint assessment using ultrasound has proven to be an accurate means for assessment of ligaments and tendons. (See 'Ultrasound' below.)

In the setting of acute injury, magnetic resonance imaging (MRI) has no major advantage over plain radiograph [38] unless other severe trauma is suspected. However, MRI may be needed for ankle sprains that remain painful after six to eight weeks of standard therapy. MRI can detect talar dome fractures and may be used to confirm suspected syndesmosis or other soft tissue injury.

Ultrasound

Application and utility — Clinicians skilled in the performance of point-of-care musculoskeletal ultrasound may choose to use it as part of their assessment, but this is not obligatory. Ultrasound can accurately identify deltoid, anterior inferior tibiofibular, and lateral ankle sprains and distinguish between partial and complete ligament rupture [39-43]. While not a replacement for plain radiographs, ultrasound can also be useful for identifying distal fibular, distal tibial, and talar fractures [44-46]. Performance of the ankle ultrasound examination is discussed in detail separately; maneuvers and findings specific to the assessment of ankle sprains are described below. (See "Musculoskeletal ultrasound of the ankle and hindfoot".)

Some studies have found high-resolution ultrasound to be as precise as MRI for identifying partial or complete ankle ligament tears [41-43,47,48]. However, the accuracy of the ultrasound examination depends upon operator skill, and studies typically involve clinicians formally trained in musculoskeletal ultrasound. While ultrasound is a useful diagnostic tool that is being used more widely, evidence that it improves outcomes is lacking.

Note that ultrasound is not a consideration when applying the Ottawa ankle rules, which are intended to determine when the risk for fracture is sufficiently high that plain radiographs are needed. Ultrasound is not proven to be sufficiently sensitive for identifying fracture and should not be used in place plain radiographs in this setting. (See 'Ottawa ankle rules' above.)

Examination procedure and findings — Ultrasound can be used for stationary and dynamic assessments of ligaments, with motion and stress applied by the examiner. The uninjured ankle should be used as a reference. (See "Musculoskeletal ultrasound of the ankle and hindfoot".)

For possible lateral ligament injury, talar tilt and anterior drawer maneuvers are used as part of the assessment [39,40,49].

On ultrasound assessment, a grade II lateral ligament ankle injury appears as a partially torn ligament with some intact fibers. Imaging performed while applying a dynamic stress to the ligament shows minimal laxity. With a grade III injury (complete ligament rupture), two key findings are present: two completely disrupted ligament ends (usually visible as stumps (image 3)) and, with anterior talofibular ligament injuries, increased space between the talus and fibular head [39,49]. Although the absolute change in the distance is small (2 to 3 mm), it has reached statistical significance in studies to date. Measured assessment can be used to assess acute injury and chronic lateral instability. Edema around injured ligaments and a joint effusion may also be seen with ultrasound (image 4 and image 5). In acute injury, better images are obtained once swelling is resolved.

DIAGNOSIS — In most cases, the diagnosis of a mild or moderately severe ankle sprain is made clinically based on a history of acute ankle trauma and suggestive examination findings. Clinicians facile with point-of-care musculoskeletal ultrasound may use this technique to assess ligament and tendon injury and function for all grades of injury, but other diagnostic imaging (including plain radiographs, CT, and MRI) is unnecessary unless the injury involved high-energy trauma or likely extends beyond an isolated ankle sprain, or the Ottawa ankle rules cannot be applied. In such cases, diagnostic imaging (most often plain radiographs) is performed to assess for other injuries.

DIFFERENTIAL DIAGNOSIS — The differential diagnosis of acute ankle sprain includes tendon rupture, tendinopathy, fracture, stress fracture, tendon subluxation, and a number of other conditions. Often, the diagnosis can be clarified based on a history of acute trauma and suggestive examination findings without the need of imaging studies. In cases of severe trauma or when the Ottawa ankle rules are not applicable, diagnostic imaging clarifies the diagnosis. (See "Musculoskeletal ultrasound of the ankle and hindfoot" and 'Diagnostic imaging' above.)

The differential diagnosis of ankle pain can often be narrowed based on the history and location of pain. A discussion of the differential diagnosis organized by location is provided separately:

●Lateral ankle pain (see "Non-Achilles ankle tendinopathy", section on 'Differential diagnosis of lateral ankle tendinopathy')

●Medial ankle pain (see "Non-Achilles ankle tendinopathy", section on 'Differential diagnosis of medial ankle tendinopathy')

●Anterior ankle pain (see "Non-Achilles ankle tendinopathy", section on 'Differential diagnosis of anterior ankle tendinopathy')

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Ankle sprain".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topic (see "Patient education: Ankle sprain (The Basics)" and "Patient education: How to use crutches (The Basics)")

SUMMARY AND RECOMMENDATIONS

●Epidemiology – Risk factors for lateral ankle sprain include limited dorsiflexion, reduced proprioception, and poor balance. Among activities, indoor court sports pose the highest risk. The mechanism of most ankle sprains involves inversion of the plantarflexed foot and damages the lateral ligaments. Medial ankle sprains are relatively uncommon. (See 'Epidemiology and risk factors' above and 'Classification of ankle sprains' above.)

●History – Perform a careful history to determine the mechanism of injury, whether the patient could walk after the injury (important for Ottawa ankle rules), and whether the ankle had been previously injured (history of ankle sprain increases risk for subsequent injury). (See 'History' above.)

●Physical examination – The physical examination should include palpation of the entire fibula, distal tibia, joint line, lateral and medial ankle ligaments, Achilles tendon, and areas covered by the Ottawa ankle rules (posterior edge or tip of the lateral malleolus, posterior edge or tip of the medial malleolus, base of the fifth metatarsal, navicular bone). The anterior drawer (picture 6) and talar tilt (picture 7) tests can help identify more severe ligamentous injury. The squeeze test (picture 4) and external rotation test (picture 5) can help identify syndesmotic injury. A deferred examination performed a few days after the injury is more accurate. (See 'Physical examination' above and 'Special tests' above.)

●Diagnostic imaging – The Ottawa ankle rules (figure 6) help to determine whether plain radiographs are necessary. (See 'Determining the need for radiographs' above and 'Ottawa ankle rules' above.)

To rule out an ankle fracture, obtain anteroposterior, lateral, and mortise plain films of the ankle, if indicated. Malleolar fractures, distal fibula fractures, talar dome fractures, and syndesmosis separation may be diagnosed with plain radiographs. (See 'Selection of imaging modality' above.)

While not obligatory, point-of-care ultrasound is a useful and accurate tool for assessing tendon and ligament injury when performed by skilled operators. (See 'Ultrasound' above.)

●Differential diagnosis – The differential diagnosis of acute ankle sprain includes tendon rupture, fracture, stress fracture, subluxation, and several other conditions. Often, the diagnosis can be clarified on the basis of a suggestive history of acute ankle trauma and examination findings without the need of imaging studies. In cases of significant trauma or when the Ottawa ankle rules are not applicable, diagnostic imaging clarifies the diagnosis. (See 'Differential diagnosis' above and 'Diagnosis' above.)

●Management – The management of ankle sprains is discussed separately. (See "Ankle sprain in adults: Management" and "Syndesmotic ankle injury (high ankle sprain)".)