The initial presentation of an acute lateral ankle injury may be deceptive. What appears to be a simple ankle sprain may represent a fracture of the ankle or hindfoot. A tendon or impingement-type injury may not present until later in the healing process. One may not be able to appreciate other intraarticular injuries without advanced imaging studies. Nerve injuries may offer the greatest diagnostic challenges of all (see “A Guide To Differential Diagnosis Of Inversion Ankle Injuries” below). The ankle is the most common joint injured in sports and ankle sprains represent 85 percent of all ankle injuries in the United States.1-5 When approaching any lateral ankle injury, it is important to ascertain whether it represents an acute or overuse injury. When evaluating an acute injury, it is important to perform a thorough physical examination and rule out the possibility of fracture. Swelling and ecchymosis may not correlate to the location of injury. Standard ankle series radiographs, including anterior-posterior, oblique and lateral views, will provide evidence of fracture to the lateral malleolus, posterior and lateral talar processes, and anterior processes of the calcaneus. If physical examination findings warrant, obtaining additional radiographs of the foot may be necessary to rule out fracture to the fifth metatarsal base as well. While an inversion ankle injury commonly leads to injury to the lateral collateral ankle ligaments, many other structures in this area may also be injured.1,6-8 One may not appreciate these associated injuries until weeks or months after the initial event. Other associated lateral ankle injuries do not manifest themselves until the patient attempts to return to full activities but is unable to do so due to persistent lateral ankle pain. Typical associated injuries include chronic lateral ankle instability, injury to the peroneal tendons, nerve injury or intraarticular injury.
Weighing The Etiology And Impact Of Chronic Lateral Ankle Instability
Following an inversion ankle sprain and particularly following repeated inversion ankle sprains, there is a risk of developing chronic lateral ankle instability due to repeated stretching or tearing of the lateral collateral ankle ligaments. The lateral collateral ankle ligaments consist of the anterior talofibular ligament, the calcaneofibular ligament and the posterior talofibular ligament. Typically, an inversion ankle sprain results in injury to either the anterior talofibular ligament or calcaneofibular ligaments.9 Frequently, both of these ligaments will be injured to some degree.1 Given its location deep to the peroneal tendons in the posterior ankle, the posterior talofibular ligament rarely sustains significant injury.3 By contrast, the anterior talofibular ligament is the most frequently injured ligament in the lateral ankle. It is also the only one of these three ligaments that is intracapsular.6 Injuries to the lateral collateral ligaments are typically classified as grade 1, 2 or 3.10 Grade 1 injuries are characterized by stretching or inflammation of one or more of the ligaments. Grade 2 injuries, which are most common, consist of partial tearing of one or more of the ligaments. Grade 3 injuries involve complete rupture of one or more of the ligaments. Early reduction of swelling and prompt initiation of physical therapy are key to regaining full function and stability.1 Outcome studies of grade 3 injuries have shown little difference between conservative and surgical treatment in terms of stability, strength and one’s ability to return to full activities.11 Without physical therapy, the ligaments will heal in a “stretched out” or loosened position that contributes to instability. Employing U-shaped padding about the lateral malleolus in combination with compression promptly after the injury can minimize the swelling. It is the persistent swelling about the ligaments that helps maintain the stretched out position. Using an ankle stabilizer brace will help support the ligaments while allowing normal ankle function and alignment. Physical therapy not only helps patients regain full strength but also facilitates proprioception, which is essential in preventing instability. While the ankle sprain is a common injury, chronic lateral ankle instability typically requires a history of recurrent inversion sprains. Patients will often complain that the affected ankle feels “unstable” or “gives out” frequently. They typically feel unsteady when walking on uneven ground or sloped surfaces. Repeat inversion injuries will occur with the slightest provocation. Not uncommonly, these patients report twisting or spraining their ankles every few months with varying levels of severity.7,12 Bracing or taping may not provide adequate stability. Clinically, physical examination findings commonly reveal persistent swelling to the anterolateral aspect of the ankle, even if there has been no recent re-injury. There may or may not be tenderness to palpation of the anterior talofibular ligament or calcaneofibular ligament. Typically, one will see a positive anterior drawer sign or anterior displacement of the talus from the tibia, similar to what clinicians would see with an acute ankle injury. There is also increased inversion of the talus in the ankle mortise, particularly when one compares this to the contralateral ankle. When there is attempted rotary motion of the ankle within the mortise, the talus will often translocate laterally.
How To Perform And Assess Talar Tilt And Anterior Drawer Tests
Specific diagnostic tests are required to definitely diagnose instability. Most practitioners perform manual stress X-rays of the ankle. Like most manual tests, accuracy and reproducibility depend on the skill of the practitioner. One can reduce this variability by using a stress device machine, which exerts a constant pressure of 15 kPa in an attempt to displace the talus within the ankle mortise. However, access to such equipment is limited. In either case, the specific diagnostic tests consist of talar inversion stress (talar tilt) and anterior displacement stress (anterior drawer). In most cases, one should apply both tests to the symptomatic as well as the asymptomatic ankle. Originally described by Farber in 1932, the talar tilt test refers to the angle formed during forceful inversion of the hindfoot between the talar dome and tibial plafond. One may perform this test by cupping the patient’s calcaneus in one’s hand, keeping the thumb clear of the ankle joint, and stabilizing the tibia with the other hand. Then the clinician would invert the calcaneus and talus as far as possible given the patient’s tolerance. The practitioner holds this position while an AP X-ray is taken. If the patient resists movement in any way, then it may be necessary to administer a local anesthetic block to the ankle. Typically, this is not necessary with manual exams but is often required when using a stress device machine. Exact measurements vary but generally the test is considered positive when the angle of talar tilt measures greater than 18 degrees or differs from the contralateral side by more than 5 degrees.7,13 The anterior drawer test consists of manipulating the affected ankle while taking a lateral X-ray view. To perform this test, it is important for the patient to lie partially on the affected side in such a manner as to obtain as true a lateral projection of the ankle as possible. The fibula should be slightly posterior to the line of the X-ray beam, mimicking its anatomic position. Placing the ankle in 10 degrees of plantarflexion improves the sensitivity of the test.14 One should perform an anterior displacement test on the talus by cupping the calcaneus and pulling forward and slightly downward with one hand while stabilizing the tibia with the other hand. There are various methods of measuring this test but typically the test is considered positive when there is a 10 mm excursion of the talus from under the tibia or 3 mm more than the contralateral side.15 Recent studies suggest that measuring the posterior excursion of the tibia from the posterior aspect of the talus may produce more reliable and reproducible measurements.16 These tests also provide insight into which ligaments may be injured. An anterior drawer test indicates injury to the anterior talofibular ligament but does not necessarily exclude injury to the calcaneofibular ligament. The talar tilt test isolates injury to the calcaneofibular ligament.9 While magnetic resonance imaging (MRI) may offer valuable information for an elite or professional athlete in the setting of an acute ankle sprain, it has little to offer when it comes to establishing a diagnosis of chronic instability. This requires dynamic testing such as the anterior drawer and talar tilt stress X-rays.17,18
Recognizing Cases Of Functional Instability
Additionally, a subset of patients may have negative stress exams but still demonstrate frequent minor inversion industries and a sense of instability to the ankle. This condition describes functional instability as opposed to mechanical instability.5,8,19,20 Under these circumstances, the ligaments may only have healed in a somewhat slightly loosened position but the patient has failed to re-establish the proprioceptive connection to the brain.21 Proprioceptive fibers are embedded within the lateral collateral ankle ligaments and sustain injury along with the ligament itself.8,21,22 One may assess proprioception in these patients by using a modified Rhomberg test. The patient stands on the normal ankle with his or her eyes open and then closed. Repeat this procedure on the symptomatic limb. Alternatively, the patient may rise onto the ball of the affected foot and perform five single leg hops.5-8 One of the key components of physical therapy is to reestablish these proprioceptive connections so the patient senses uneven surfaces and can recruit other muscles to stabilize the ankle and avoid inversion injury.23,24 Other contributors to functional instability include impaired joint position sense, delayed peroneal muscle reaction time, altered common peroneal nerve function and muscle weakness.5,8
Pearls For Diagnosing Peroneal Tendon Injuries
Injury to the peroneal tendons can manifest in several ways, including peroneal tendon tears, tenosynovitis and subluxation. During an inversion injury, the peroneus brevis and peroneus longus tendons fire in an attempt to evert the foot forcibly, thereby stabilizing the ankle to prevent it from inverting.25 This can result in a subtle, longitudinal tear to one of the tendons. The peroneus brevis tendon is commonly injured given its close proximity to the posterolateral tip of the fibula.26 Additional contributing factors may attenuate the superior peroneal retinaculum. These factors include an anomalous tendon or low-lying peroneal muscle belly.27 This condition constrains the peroneal tendon within the fibular groove, leading to mechanical attrition of the peroneus brevis tendon against the sharp posterior ridge of the fibula.8,26,28,29 Many of these subtle injuries heal uneventfully. Occasionally, however, the patient will complain of persistent pain posterior to the lateral malleolus that is exacerbated by lateral cutting maneuvers such as the swift side-to-side motion one frequently sees in tennis or soccer, or abrupt changes in direction that occur when pivoting on one foot. Swelling may or may not be present but one may frequently reproduce pain via palpation of the tendons posterior to the lateral malleolus and through resisted ankle eversion. Frequently, clinicians may see evidence of a tear on a MRI as indicated by a C-shaped appearance to the tendon on an axial projection with abundant scar tissue formation surrounding the tendon and increased fluid signal on T2 STIR sequences.28,30,31,32 Magnetic resonance imaging may also help distinguish between a discrete tendon tear and less serious conditions of tendonitis or tendonosis although chronic tendonosis may be a precursor to an actual tear.30 Comparing T1 and T2 images at the distal tip of the fibula will help clarify potential “false positive” findings due to the magic angle phenomenon.28,31 Bear in mind that a normal study does not preclude surgical intervention under appropriate clinical circumstances. However, one cannot appreciate peroneal tenosynovitis on MRI. In order to diagnose this condition, which involves hypertrophic synovium within the peroneal tendon sheath within the tendons themselves, one should use a tenogram.33 When the tenogram is positive, the flow of radioopaque dye will be impeded by adhesion or stricture of the sheath or scar tissue about the tendon.34 Additionally, a tenogram may be potentially therapeutic as well as diagnostic. The mixture of local anesthetic and radioopaque dye into the closed space of the tendon sheath acts as a “balloon” to separate the adherent scar tissue from the surface of the tendon. Adding corticosteroid into the injection may potentially “shrink” any adhesive scar tissue and decrease inflammation. Given the risk of tendon rupture with corticosteroid injection to tendons, this procedure requires a skilled radiologist to ensure an injection into the space between the tendon sheath and the actual tendon itself. Subluxation of the peroneal tendons may occur for anatomical reasons or as a result of an inversion injury but the subluxation is often overshadowed by a lateral collateral ligament injury.35 During an inversion injury and particularly following repeated ankle sprains, the peroneal retinaculum may be stretched and no longer retain the tendons posterior to the lateral malleolus.26,27 If the patient has an anatomically shallow fibular groove, then even a subtle injury to the retinaculum may cause the tendons to slide anteriorly.34,36 Recent studies also suggest that a more posterior anatomic position of the fibula may also contribute to instability, influencing the ability of the peroneal tendons to stabilize the ankle.37 Patients will often complain of sudden sharp pain to the lateral ankle with lateral cutting maneuvers, pivoting or rising onto the balls of the feet.34 Swelling may or may not be present. Often, during the physical exam, the physician can feel the tendons snap or slide anterior to the fibula by palpating the area while the patient either rotates the foot in a circular motion or rises onto the balls of the feet. One may not appreciate subtle sliding of the tendons on examination. Obtaining a MRI can aid in diagnosis since it will show evidence of stretching or scarring of the peroneal retinaculum as well as decreased concavity of the peroneal groove.6,7,26,28-30
Recognizing Potential Nerve Injuries
Nerve injuries are often the last category of injury clinicians consider when diagnosing lateral ankle problems. Nerve symptoms may include pain, burning, tingling or numbness. The symptoms will often radiate distally or proximally. The symptoms may or may not be related to activity but will often relate to the position of the foot or pressure from shoes.38 Any inversion injury has the potential to place traction on the sural nerve as it runs alongside the peroneal tendons. Additionally, the superficial peroneal nerve becomes superficial in close proximity to the anterior talofibular ligament and may become partially entrapped in scar tissue as injury to the ligament heals. Blunt trauma may cause direct injury to the nerve itself, resulting in neuropraxia. Patients may complain of sharp pain with sudden pivoting movement or any compression of the anterior of the lateral ankle, which may occur in high-topped boots or ski boots.39 Other complaints may consist of either transient or constant numbness, and periodic tingling or burning sensations. Symptoms may be worse at night than during the day. More serious injuries, such as plantarflexion inversion injuries, may result in traction injury to either the sural or common peroneal nerves, leading to axonotemesis or neurotemesis, depending on the severity. Specifically, plantarflexion inversion injury causes constriction of the peroneus longus at the level of the common peroneal nerve, entrapping the nerve as it passes underneath the muscle. Physical exam findings may indicate allodynia, decreased sensation to light touch, an inability to distinguish between sharp and dull stimuli and decreased two-point stimulation. Manual percussion of the affected nerve precipitates distal paresthesias (positive Tinel’s sign) or more infrequently proximal paresthesias (positive Valleix’s sign).5,40 Swelling about the affected area is rarely present. Severe injuries of the common peroneal nerve may cause paralysis and muscle atrophy, leading to foot drop.5,41 More sophisticated diagnostic studies are often necessary, particularly when it comes to distinguishing between local nerve injury and a possible correlation to any associated or past low back injury. One should suspect radiculopathy in any patient who exhibits positive proximal findings, particularly in a positive straight leg raise test. Electrodiagnostic studies, including nerve conduction studies, may be key in ruling out radiculopathy or mononeuropathy in these patients.5,39
What You Should Know About Intraarticular Injuries
In the lateral ankle, intraarticular injuries typically consist of impingement syndromes, chondral and osteochondral lesions. Chondral lesions involve only the articular cartilage while osteochondral lesions consist of injury to the cartilage and the underlying bone.42 Occasionally, a talar dome lesion may be visible on initial X-ray following an inversion injury or a patient may have a loose body present from a prior injury that appears on a X-ray. However, these injuries frequently do not manifest until later in the healing process or once the patient returns to regular activity. Chronic ankle instability has a higher incidence of osteochondral lesions than acute distal fibular fracture.43 The patient may complain of periodic “clicking,” “popping” or “locking” of the ankle. Frequently, these occurrences are random. There may be persistent pain to the anterolateral ankle that often occurs with end-range dorsiflexion, especially with impact activities or walking uphill. Patients often describe the pain as a dull, aching sensation about the ankle joint.3,44 Chondral and osteochondral lesions typically involve the posterior medial and anterior lateral aspects of the talus.45,46 Posterior medial lesions frequently are less symptomatic and not always associated with trauma. Anterior lateral lesions are associated with trauma in nearly 100 percent of cases.44-47 One should maintain a high index of suspicion in patients who have persistent pain despite normal radiographs or those who fail to improve after traditional treatment following a routine ankle sprain. Physical examination may reveal persistent focal swelling to the anterior lateral ankle with pain to palpation of this area, particularly with the ankle in plantarflexion. Crepitus may be present and pain may increase with tibial talar compression. The presence of an intraarticular loose body may precipitate locking. In late stages, the presentation will be consistent with an arthritic joint. Although some osteochondral lesions may be visible on plain radiographs, which provide the basis for the Berndt-Hardy classification, a MRI provides more specific evidence of pathology.45 Various sequences highlight different tissues, contrast and spatial resolution. Fat-suppressed proton density-weighted or T2-weighted sequences (STIRs) are often the most sensitive for detecting contusion or trabecular injury to the underlying bone.3 Bone marrow edema adjacent to chondral defect generally indicates that the lesion is active or likely symptomatic. One may use MRI to help assess and track healing of lesions over time. Impingement syndromes generally result from hyalinized fibriolysis of the hemarthrosis associated with lateral ankle ligament injury, leading to posttraumatic synovitis within the anterolateral gutter.48,49 This inflamed scar tissue, which may be triangular or meniscoid in shape, impinges on the anterolateral margin of the talar dome, causing pain and decreased range of motion.20,50 Over time, this may cause repetitive abrasion of the chondral surface and erosion of the articular cartilage. In impingement syndromes, the clinical examination may reveal chronic edema to the anterolateral ankle in the location of the anterior talofibular ligament. There is pain to palpation in this region or one may only produce pain with provocation such as closed chain dorsiflexion of the ankle. There may be resistance to attempted rotary motion of the ankle as well as decreased ankle joint dorsiflexion compared to the contralateral side. Plain X-rays may reveal the presence of an osseus intraarticular loose body. Whether this is present or not, obtaining a MRI will help determine the location of the loose body and can also detect excessive scar tissue or meniscoid bodies that may be limiting joint motion and contributing to persistent painful synovitis.3
Assessing The Potential Impact Of Orthotic Solutions
Given that a significant percentage of chronic lateral ankle problems is associated with either a flexible or rigid forefoot valgus deformity, functional foot orthoses offer an effective adjunct to the overall management of this condition. When functional foot orthoses address the lateral column instability of the foot (by supporting the everted forefoot position via intrinsic or extrinsic forefoot posting), patients experience dramatic improvement with regard to their lateral instability. This is particularly true in the case of rigid forefoot valgus deformity, in which the foot functions with an inverted rearfoot from heel contact through the propulsive phase of gait. Additionally, a flexible forefoot valgus foot type that compensates via supination of the longitudinal axis of the midtarsal joint will also benefit via lateral stabilization. Even individuals who pronate excessively demonstrate an improvement of their lateral instability when they utilize a functional forefoot orthosis as the locking mechanism of the midfoot and midtarsal joint is allowed to function in a more appropriate fashion.19,51 However, there are some cases in which inverting the foot may exacerbate some cases of lateral ankle instability. In these cases, it is appropriate to pronate the foot maximally during the casting procedure and introduce an iatrogenic forefoot valgus deformity. One may then instruct the orthotics laboratory to correct the valgus deformity with the patient stabilized in this pronated position. Clinicians should then consider the presence of a limb length inequality as contributing to lateral ankle instability. A shortened limb may often function in a more supinated or inverted fashion in an attempt to equalize leg length. In these cases, employing a heel lift with or without a functional foot orthosis may prove successful in increasing stability.52,53
A Guide To Differential Diagnosis Of Lateral Ankle Injuries
Lateral collateral ligament sprain Syndesmosis sprain (high ankle sprain) Lateral malleolar fracture Lateral talar process fracture Anterior process calcaneus fracture Subtalar injury Fifth metatarsal base fracture Peroneal tendon injury Osteochondral injury Peroneal nerve injury Sural nerve injury Calcaneocuboid injury Intraarticular loose body/impingement
Key Contributing Factors To Inversion Ankle Injuries
Ligamentous laxity Ankle varus Tibial varum Forefoot valgus Uncompensated equinus Rigid plantarflexed first ray Peroneal muscle weakness Limb length discrepancy Supinated subtalar joint Prior inversion ankle injury
Many different lateral ankle injuries may have similar presentations and more subtle injuries may be overshadowed by the initial acute trauma. Ensuring a thorough understanding of the acute and functional aspects of lateral ankle injuries will allow practitioners to provide effective and efficient care for patients presenting with these injuries. Dr. Ardizzone is a Staff Podiatrist at the Center for Sports Medicine at St. Francis Memorial Hospital in San Francisco, Calif. She is an Associate of the American College of Foot and Ankle Surgeons. Dr. Valmassy is a Staff Podiatrist at the Center for Sports Medicine at St. Francis Memorial Hospital in San Francisco, Calif. He is a Fellow of the American College of Foot and Ankle Orthopedics and Medicine. Dr. Valmassy is also a Diplomate of the American Board of Podiatric Orthopedics and Primary Podiatric Medicine. For related articles, see “How To Manage Lateral Ankle Sprains In Athletes” in the November 2003 issue or “Revisiting A Proven Approach To Severe Ankle Instability” in the November 2004 issue of Podiatry Today. Also be sure to visit the archives at www.podiatrytoday.com.
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CE Exam #135
Choose the single best response to each question listed below.
1. Injuries to the lateral collateral ligaments generally heal within:
a) One week
b) One to two weeks
c) Three to four weeks
d) Four to six weeks
e) Eight to 12 weeks
2. Which of the following does not contribute to persistent lateral ankle pain?
a) Osteochondral defect of the talus
b) Neuropraxia of the deep peroneal nerve
c) Tendon sheath tear of the peroneus brevis
d) Tendon sheath tear of the peroneus longus
e) Compensated rigid forefoot valgus
3. Stress testing in the ankle requires a force equivalent to:
a) 5 kPa
b) 10 kPa
c) 15 kPa
d) 20 kPa
e) 25 kPa
4. A positive anterior drawer sign is consistent for an injury to the:
a) Body of the talus
b) Sustentaculum tali
c) Posterior process of the calcaneus
d) Peroneus tertius
e) Anterior talar fibular ligament
5. A positive inversion stress is noted when talar tilt measures ...
a) 0 to 3 degrees
b) 3 to 6 degrees
c) 6 to 12 degrees
d) 12 to 18 degrees
e) 18 to 24 degrees
6. Four millimeters of excursion of the talus from under the tibia is consistent with:
a) Positive posterior drawer sign
b) Tear of the peroneus longus tendon sheath
c) Neuropraxia of the sural nerve
d) Tear of the anterior talar fibular ligament
e) Osteochondral defect of the talus
7. Which of the following is most likely to contribute to chronic lateral ankle instability?
a) Forefoot supinatus of 10 degrees
b) Rigid forefoot valgus of 8 degrees
c) Flexible forefoot valgus of 5 degrees
d) Compensated rearfoot varus
e) 18 degrees of tibial torsion
8. A positive talar tilt test confirms injury to which of the following?
a) Sinus tarsi
b) Cartilage overlying the talus
c) Calcaneal fibular ligament
d) Peroneus brevis
e) Posterior talar fibular ligament
9. Appropriate physical therapy for the initial treatment of an inversion ankle injury involving a ruptured lateral collateral ligament does not include:
c) Laced-up ankle brace
d) Contrast baths
e) Massage therapy
10. Which of the following does not enhance increased ankle proprioception?
a) Ankle brace
b) Functional foot orthosis
c) High-heeled shoes
d) U-shaped padding
e) Contrast baths
Instructions for Submitting Exams
Fill out the enclosed card that appears on the following page or fax the form to the NACCME at (610) 560-0502. Within 60 days, you will be advised that you have passed or failed the exam. A score of 70 percent or above will comprise a passing grade. A certificate will be awarded to participants who successfully complete the exam. Responses will be accepted up to 12 months from the publication date.