Evaluation and Treatment of Ankle Sprains
Clinical Recommendations for a Positive Outcome
R. Todd Hockenbury, MD; G. James Sammarco, MD
THE PHYSICIAN AND SPORTSMEDICINE - VOL 29 - NO. 2 - FEBRUARY 2021
In Brief: Ankle sprains usually involve damage to lateral ankle ligaments and syndesmotic ligaments. A detailed examination that focuses on physical examination techniques is important because other injuries may mimic ankle sprains, and hands-on grading of ankle sprains dictates treatment and forecasts recovery time. Most ankle sprains can be successfully treated nonsurgically with PRICE (protection, rest, ice, compression, and elevation). When patients experience chronic pain or instability from an ankle sprain, a directed approach will help physicians fine-tune nonsurgical treatments or suggest a surgical referral.
Sprain of the lateral ankle ligaments is the most common injury seen by healthcare providers who treat sports injuries to the lower extremity (1,2). Ankle injuries constitute 25% of all sports-related injuries (3), including 21% to 53% of basketball injuries and 17% to 29% of all soccer injuries (4,5). One third of all West Point cadets sustain an ankle sprain during their 4-year tenure (6).
Anatomy and Biomechanics
The ankle is a simple hinge joint. The stability of the talocrural joint depends on both joint congruency and the supporting ligamentous structures. The lateral ankle ligaments (figure 1A), responsible for resistance against inversion and internal rotation stress, are the anterior talofibular ligament (ATFL), the calcaneofibular ligament (CFL) and the posterior talofibular ligament (PTFL). The medial supporting ligaments are the superficial and deep deltoid ligaments, which are responsible for resistance to eversion and external rotation stress and are less commonly injured.
The ATFL resists ankle inversion in plantar flexion, and the CFL resists ankle inversion during dorsiflexion (7-10). The accessory functions of the ATFL are resistance to anterior talar displacement from the mortise, clinically referred to as the anterior drawer, and resistance to internal rotation of the talus within the mortise. The CFL spans both the lateral ankle joint and lateral subtalar joint, thus contributing to both ankle and subtalar joint stability (11). The PTFL is under greatest strain in ankle dorsiflexion and acts to limit posterior talar displacement within the mortise as well as talar external rotation (12).
Clinically, the most commonly sprained ankle ligament is the ATFL, followed by the CFL. The PTFL is rarely injured. The incidence of ligamentous injury tends to match both the mechanism of injury and relative ligamentous strength. The strength of the ankle ligaments from weakest to strongest is the ATFL, PTFL, CFL, and deltoid ligament (13).
Lateral ankle sprains occur as a result of landing on a plantar flexed and inverted foot. These injuries occur while running on uneven terrain, stepping in a hole, stepping on another athlete's foot during play, or landing from a jump in an unbalanced position. During periods of ankle unloading, the ankle rests in a position of plantar flexion and inversion. If the ground or another object is met unexpectedly by the unloaded foot, lateral ligament injury may occur.
The subtalar joint lies inferior to the ankle joint and is responsible for inversion and eversion of the hindfoot. The subtalar joint controls foot supination and pronation in close conjunction with the transverse tarsal joints of the middle foot. The CFL provides stability to inversion and torsional stresses to both the ankle and subtalar joints. Up to 50% of apparent ankle inversion observed actually comes from the subtalar joint (11). The structures that contribute to stability of the subtalar joint are the CFL, the cervical ligament, the interosseous ligament, the lateral talocalcaneal ligament, the fibulotalocalcaneal ligament (ligament of Rouviere), and the extensor retinaculum (14).
The syndesmotic ligaments, responsible for maintaining stability between the distal fibula and tibia, consist of the anterior tibiofibular ligament, the posterior tibiofibular ligament, the transverse tibiofibular ligament, the interosseous ligament, and the interosseous membrane (figure 1B). Injuries to the ankle syndesmosis occur as a result of forced external rotation of the foot or during internal rotation of the tibia on a planted foot. A common mechanism is a direct blow to the back of the ankle while the patient is lying prone with the foot externally rotated. These injuries more commonly occur in contact sports and skiing (15). Among 96 ankle sprains reported at West Point, 17% were sprains of the syndesmosis (16).
A detailed, complete examination is essential to avoid misdiagnosis or overlooking associated injuries. The ATFL, CFL, distal tibiofibular syndesmotic ligaments, deltoid ligament, lateral malleolus, and medial malleolus should be carefully palpated with one finger. The fifth metatarsal base, anterior process of the calcaneus, Achilles tendon, peroneal tendons, and posterior tibial tendon should also be palpated, because injuries to these structures may mimic ankle sprains. Swelling is usually seen laterally but may be diffuse. Ecchymosis is also frequently found laterally, but it may settle into the lateral or medial heel. A careful neurologic examination is essential to rule out loss of sensation or motor weakness, as peroneal nerve and tibial nerve injuries are sometimes seen with severe lateral ankle sprains (17).
Provocative tests for lateral ankle instability include the anterior drawer test, inversion stress test, and the suction sign (figure 2). Two provocative tests for syndesmotic ligament injury are the squeeze test and the external rotation stress test (figure 3).
Every swollen, painful, twisted ankle does not require a radiograph to rule out fracture. The decision to obtain postinjury radiographs is based on the Ottawa ankle rules (18). These guidelines state that an ankle radiographic series (anteroposterior, oblique, and lateral views) should be obtained if bone tenderness is present over the lateral or medial malleolus, or if the patient is unable to bear weight for four steps both immediately postinjury and in the emergency department. Exclusions for use of the Ottawa ankle rules are age younger than 18 years, intoxication, multiple painful injuries, pregnancy, head injury, or diminished sensation due to neurologic deficit. These criteria have been found to be 100% sensitive for detecting fracture while decreasing the incidence of unneeded radiographs (18).
Radiographs. If radiographs are warranted, they should be examined for fractures of the medial, lateral or posterior malleoli, talar dome, lateral talar process, and anterior calcaneal process. Injuries to the distal syndesmotic ligaments and deltoid ligament will produce widening of the ankle mortise that is manifested by increased medial clear space and lateral talar subluxation. A fracture of the posterior rim of the distal fibula, known as a "flake fracture," may be associated with a tear of the superior peroneal retinaculum that occurs during dislocation of the peroneal tendons (19). Foot radiographs should also be obtained if the physical examination demonstrates tenderness in the hindfoot, middle foot, or forefoot.
Stress radiographs. Stress radiographs help document lateral ligamentous ankle injury but are not required to make the diagnosis of an acute ankle sprain. Talar tilt stress radiographs and anterior drawer stress radiographs are primarily used to document mechanical instability as a cause of chronic lateral ankle instability. Either test may be performed with or without a mechanical testing apparatus. Local or nerve block anesthesia is recommended by some authors (7,20) to prevent muscle guarding, relax muscles, and decrease pain during stress testing. We feel that injecting 5 mL of local anesthetic (usually 1% xylocaine) near the lateral ankle ligaments and sinus tarsi promotes peroneal muscle relaxation and yields a more reliable test.
Talar tilt testing is performed by taking an anteroposterior or mortise view of the ankle while applying inversion stress to the slightly plantar flexed ankle. The angle between the superior aspect of the talar dome and the tibial plafond is measured to yield the talar tilt angle.
The true stress radiologic criteria for diagnosing mechanical lateral ankle instability are controversial. Normal talar tilt values have been reported to range from 0° to 23° (21,22). Because of the wide variance of normal values, some authors feel that this test is not a reliable indicator of ankle instability (22). Others argue that anteroposterior and lateral stress views do not take into account the rotational instability that is occurring at the ankle and subtalar joint (23). This may explain the complaints of subjective ankle instability in the face of normal radiographic stress tests ("functional instability"). One study (24) demonstrated that a 10° difference in talar tilt between the injured and uninjured ankle was diagnostic of a sprain of both lateral ankle ligaments in 97% of cases. Most authors agree that a difference of 5° to 15° between the injured and uninjured side is diagnostic of mechanical ankle instability (25).
Anterior drawer stress radiographs are obtained by taking a lateral view of the ankle while attempting to translate the talus anteriorly within the mortise, as in the clinical anterior drawer test. The anterior drawer is measured as the shortest distance between a point on the posterior aspect of the distal tibial articular surface and a point on the posterior aspect of the talar dome. A difference of more than 3 mm between injured and uninjured ankles is thought to be diagnostic of anterior talofibular ligament laxity (26).
Other stress tests include a view of the subtalar joint (a stress Broden's view) obtained by internally rotating the leg 45° and angling the radiographic tube 45° cephalad. This test has been used by some authors (27), but recent studies (28,29) have questioned its validity in diagnosing subtalar instability.
A mortise stress radiograph of the ankle syndesmosis can be obtained by placing an external rotation force on the ankle while stabilizing the proximal tibia with the knee flexed 90°. Abnormal widening of the mortise and lateral talar shift indicate distal syndesmotic instability. A lateral radiograph during external rotation stress will show posterior distal fibular translation and is reported to be a more accurate way to diagnose instability of the syndesmosis (30).
Magnetic resonance imaging. Magnetic resonance imaging (MRI) will confirm acute injuries to the ATFL or CFL, but it is not required to make the diagnosis (31). MRI is most useful for the evaluation of causes of chronic ankle pain following ankle ligament injury. MRI can diagnose talar dome injuries, peroneal tendon tears, bone bruises, or other occult fractures.
Grading Is a Useful Tool
Grading of ankle sprains guides treatment, rehabilitation, and prognosis. The West Point ankle sprain grading system is a useful tool (table 1) (16). The time to return to sporting activities averages 11 days for grade 1 sprains, 2 to 6 weeks for grade 2 sprains, and 4 to 26 weeks for grade 3 sprains (32-34).
Emphasis on Early Treatment
Ligamentous injuries undergo a series of phases during the healing process: hemorrhage and inflammation, fibroblastic proliferation, collagen protein formation, and collagen maturation (35,36). The more severe the ligament injury, the greater the time required to progress through the stages of healing. Early mobilization of joints following ligamentous injury actually stimulates collagen bundle orientation and promotes healing, although full ligamentous strength is not reestablished for several months (25,37-40). Therefore, early treatment focuses on regaining range of motion while protecting the injured ligaments against reinjury. Limiting soft-tissue effusion speeds healing (25,34,41).
The standard early treatment following an acute ankle sprain is PRICE (protection, rest, ice, compression, and elevation). Cryotherapy, compression, and elevation are essential to limit initial swelling from hematoma and edema around the ankle and speed ligamentous healing. Early use of cryotherapy, applied in the form of ice bags, a cold whirlpool, or a commercially available compressive cuff filled with circulating coolant, has been shown to enable patients to return to full activity more quickly (42). Compression can be applied by means of an elastic bandage, felt doughnut, neoprene or elastic orthosis, or pneumatic device.
Early mobilization. Protected weight bearing with an orthosis is allowed, with weight bearing to tolerance as soon as possible following injury. Crutches are used until pain-free weight bearing is achieved. Generally, the higher the grade of sprain, the longer it takes to achieve pain-free weight bearing.
Bracing. Protection of the ankle during initial healing is essential. This may be accomplished with taping, a lace-up splint, a thermoplastic ankle stirrup splint, a functional walking orthosis, or a short leg cast. Flexible and semiflexible braces have been shown to effectively limit ankle inversion and to resist passive torque (43). More severe injuries usually require longer immobilization. Generally, protected range of motion is superior to rigid immobilization with a cast. Early protected range of motion in a flexible or semirigid orthosis is superior to rigid cast immobilization in terms of patient satisfaction, return of motion and strength, and earlier return to function (44,45).
Rehabilitation. Physical therapy of the injured ankle is divided into five phases: acute, subacute, rehabilitative, functional, and prophylactic (46). The exact timing of each phase varies with the severity of the sprain. The acute phase is based on PRICE with goals to limit effusion, reduce pain, and protect from further injury. The subacute phase focuses on decreasing and eliminating pain, increasing pain-free range of motion, continuing protection against reinjury with bracing, limiting loss of strength with isometric exercises, and continuing modalities to decrease effusion. The rehabilitative phase emphasizes regaining full pain-free motion with joint mobilization and stretching, increasing strength with isotonic and isokinetic exercises, and employing proprioceptive training. The functional phase focuses on sports-specific exercises with a goal of returning the patient to sports participation. The prophylactic phase seeks to prevent recurrence of injury through preventive strengthening, functional proprioceptive drills, and prophylactic support as needed (46).
Nonsurgical Treatment Results
Primary surgical repair of the torn lateral ankle ligaments has been advocated by some (47-50) as treatment for elite athletes and young adults, assuming that anatomic repair will speed healing and improve long-term outcome. However, primary ligamentous repair has not been supported in comparative studies (51-53) that recommend early nonoperative functional treatment of ankle ligament injuries. Satisfactory healing of the lateral ankle ligaments with the use of a functional ankle brace has been documented by MRI (31).
Numerous studies (31,54-57) have documented that satisfactory subjective and clinical stability have been restored with nonoperative treatments such as casting, taping, bracing, and early physical therapy. A prospective study (56) of 146 patients with grade 3 ankle sprains who were randomized into operative or nonoperative groups found that the group treated with an ankle orthosis for 6 weeks returned to work faster. No difference in joint laxity between the groups was found on stress radiographs performed 2 years postinjury.
Syndesmotic ligamentous injuries without fracture or gross widening of the ankle mortise are treated nonoperatively with a short leg cast or brace, followed by physical therapy. The patient should be advised that these injuries result in longer periods of disability than injuries to the lateral collateral ligaments. In one study (16), only 44% of 16 patients had an acceptable outcome at 6 months. Heterotopic ossification of the distal syndesmosis has been reported in up to 25% of patients, though no correlation between ossification and functional outcome has been found (58). If diastasis of the syndesmosis is evident on plain radiographs, operative stabilization of the ankle mortise is accomplished with a syndesmotic screw.
Evaluating Chronic Symptoms
Chronic pain following ankle injury is common. In a retrospective study (8) of 457 patients treated with immobilization or bracing, 72.6% reported residual symptoms at 6 to 18 months. A study (16) of 96 ankle sprains in West Point cadets noted residual symptoms in 40% of ankles at 6 months postinjury.
Pain. Initial workup should center on whether the patient's chief chronic ankle complaint is pain or instability (figure 4). If the primary problem is ankle pain, a concentrated effort should be made to rule out occult fracture of the foot or ankle. A technetium bone scan is an excellent screening test to rule out occult fractures and to guide further treatment. If the bone scan reveals increased uptake in a discrete area, a spot radiograph or computed tomography scan is useful to further identify the exact location of fracture. Occult or associated injuries to the tendons of the foot and ankle should also be considered, and MRI is the most useful exam to identify and confirm them. Table 2 lists some commonly missed occult fractures and tendon pathologies.
Other soft-tissue causes of chronic ankle pain include anterolateral ankle impingement (meniscoid lesion), anteroinferior tibiofibular ligament impingement (Basset's ligament), and anomalous peroneal pathology. Injury to the lateral ankle ligaments may produce scarring of the ATFL and joint capsule, leading to the formation of "meniscoid tissue" in the anterolateral ankle. Anterolateral impingement can develop when inflamed tissue is pinched between the talus, fibula, and tibia (59). The distal fascicle of the anteroinferior tibiofibular ligament may abrade the anterolateral surface of the talus when the ankle is dorsiflexed during abnormal anterior translation of the talus (60). An anomalous or accessory peroneal tendon may also cause chronic posterolateral ankle pain (61).
Instability. If the primary problem is ankle instability, the patient will experience feelings of "giving way" of the ankle on uneven ground, inability to play cutting or jumping sports, loss of confidence in ankle support, reliance on braces, and a history of multiple ankle sprains. If, on further evaluation, stress radiographs are positive for mechanical lateral ligamentous laxity, surgery is indicated to reconstruct the loose ligaments.
If stress radiographs are nondiagnostic for mechanical laxity, the patient may have functional ankle instability due to deficient neuromuscular control of the ankle, impaired proprioception, and peroneal weakness (62,63). Treatment in this case should be directed toward restoring peroneal tendon strength and ankle motion and improving ankle proprioception with physical therapy. Other causes of instability, not demonstrated by stress radiographs, include rotational instability of the talus, subtalar instability, distal syndesmotic (tibiofibular) instability, and hindfoot varus malalignment (23).
When to Consider Surgery
Surgical treatment of lateral ligamentous ankle laxity should be considered after a full course of physical therapy and a trial of bracing have been attempted, the patient continues to experience multiple episodes of lateral ankle instability, and mechanical problems are documented by stress radiographs. Most procedures are designed to tighten or reconstruct the ATFL and CFL.
Following lateral ankle ligamentous reconstruction, most postoperative regimens immobilize the ankle in a cast for 4 weeks followed by an orthosis for an additional 4 weeks. Physical therapy with an emphasis on peroneal strengthening and propioceptive training is instituted 6 to 8 weeks after surgery. Return to sports occurs at about 3 months postsurgery.
Dr Hockenbury is an orthopedic surgeon at River City Orthopedic Surgeons in Louisville, Kentucky, and a clinical professor at the University of Louisville. Dr Sammarco is an orthopedic surgeon at the Center for Orthopedic Care in Cincinnati and a volunteer professor at the University of Cincinnati. Address correspondence to R. Todd Hockenbury, MD, University of Louisville, River City Orthopedic Surgeons, PSC, Old Third Street Rd, Suite 105, Louisville, KY 40272.