Lateral ankle sprains are defined as traumatic injury to the lateral ankle ligament complex due to an inversion injury or plantar flexion and adduction and are one of the most common injuries in sportive as well as recreational activities.
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Epidemiology
Lateral ankle sprains are the most common ankle injuries with an estimated incidence of 0.2% per year. About half of lateral ankle sprains are due to sports injuries, and they account for many athletic injuries 1-5. The most common ankle injury is ankle sprain and of ankle sprains, a lateral ankle sprain is by far the most common, accounting for up 75-80% of ankle sprains 1. There is a higher incidence in children and adolescents than in adults 2,3. Women are thought to be more frequently affected 2,4.
Risk factors
The following team sports have an increased incidence in lateral ankle sprain 1-4:
basketball, volleyball (indoor), handball, netball, aero ball
field hockey, cricket
football (soccer), Gaelic football
rugby, Australian football
In addition, the following sports or activities are considered risk factors 1,2:
gymnastics, cheerleading, martial arts
squash/badminton
orienteering, mountaineering
wall and rock climbing
field events in track and field athletics, running, jogging, ultramarathon
parachuting
scooter
Further non-sports-related risk factors are 3-5:
high-heeled shoes
previous ankle sprain
increased body mass index
impaired proprioception
impaired postural balance or neuromuscular deficits
strength deficits
Associations
anterior talofibular ligament injury (in about 73% of ankle sprains)
posterior talofibular ligament injury (uncommon)
talocrural joint capsule injury
subtalar joint injury
Clinical presentation
Typical complaints are acute pain and swelling after an unlucky landing or sudden turn during sports activity, or a misstep, “slipping” or “tripping” in daily routine activities 3,4. Stiffness, weakness, crepitus and instability are other complaints 1. A lateral ankle sprain is usually diagnosed based on clinical signs such as tenderness, hematoma and a positive anterior drawer test 3. Excessive medial translation of the calcaneus on the talus can be additionally assessed with the subtalar glide test 5.
Grading
Ankle ligament sprains can be graded according to severity 8:
grade 1: sprain without macroscopic tear/rupture or joint instability
grade 2: partial rupture with moderate pain and swelling
grade 3: complete rupture with swelling hematoma and pain
Complications
chronic ankle instability (in particular in repetitive cases – up to 38% for ≥5 ankle sprains) 1,3,5
Pathology
The pathological correlate of a lateral ankle sprain is often an anterior talofibular ligament injury and/or calcaneofibular ligament injury with possible other associated injuries such as a talocrural joint capsule injury or ligamentous injuries of the subtalar joint. Additionally, injury to the tibialis posterior, peroneus brevis or longus tendon can occur 3,4.
Mechanism
The typical mechanism of a lateral ankle sprain is a result of excessive ankle supination of the hindfoot in an externally rotated leg leading to an inversion type injury. Inversion injuries often occur with the foot in plantar flexion and internal rotation or with internal rotation and slight dorsiflexion 5. This causes a strain or distraction forces across the whole anterolateral ankle, in particular, the anterior talofibular and the calcaneofibular ligaments 4,5. If the tensile strengths of those ligaments are surpassed they sustain injury and tear or rupture.
Depending on the ligamentous injury this can lead to anterolateral rotary instability (anterior talofibular ligament injury) and/or talar tilt (calcaneofibular ligament injury) and additional problems depending on the type of additional injury.
Radiographic features
For initial evaluation of an ankle injury radiographs of the ankle are usually obtained to exclude a fracture or fracture-dislocation. Further imaging of ankle injuries can be done with ultrasound or magnetic resonance imaging 2.
Plain radiograph
Lateral and AP views of the ankle and/or Mortise views can be initially performed to exclude fractures. They may show an avulsion fracture, joint effusion and/or soft tissue swelling.
Stress radiographs had been used for the quantification of subtalar tilt but similar information can be obtained clinically with the subtalar glide test 5.
CT
CT can better illustrate subtle fractures, detect avulsion fractures or show a higher-grade osteochondral injury.
Ultrasound
Ultrasound findings include thickening and hypoechogenicity of the affected ligament in case of a sprain. A tear will show an anechoic defect, a loss of continuity or absence of the ligament.
MRI
Common indications include prolonged pain after conservative management, or to exclude more extensive injuries. MRI can demonstrate anterior talofibular ligament and/or calcaneofibular ligament injury as well as injuries of flexor or the peroneal tendons.
Furthermore, MRI can exclude syndesmotic injury, osteochondral injury and or injury to the midtarsal joint, which can lead to treatment failure if not diagnosed 8.
The anterior talofibular ligament can be assessed in axial slices or oblique axial slices with a mild anteroinferior tilt in the suspected course of the ligament. The calcaneofibular ligament is best evaluated on oblique axial/coronal with a posteroinferior tilt again in the suspected course of the ligament and on coronal images.
Ligament injury might reveal thickening, thinning, irregularity, discontinuity or an absent ligament. Sometimes bony avulsions can be seen.
Radiology report
In case of a lateral ankle sprain the report should include the following:
anterior and/or posterior talofibular ligament injury (sprain, partial tear, complete tear)
calcaneofibular ligament injury (sprain, partial tear, complete tear)
concomitant subtalar joint or midtarsal injury
concomitant or old avulsion injuries of the lateral malleolus
possible injuries of the peroneal and flexor tendons
possible concomitant syndesmotic injury
fractures or fracture-dislocations
chondral or osteochondral injury
Treatment and prognosis
Lateral ankle sprains are usually treated conservatively with rest, ice, compression and limb elevation, also referred to as RICE (rest, ice, compression, elevation) regimen in the initial phase 3,8.
In addition, external stabilization can be beneficial in the initial period for protection from inversion and to prevent uncontrolled stresses. Best results are apparently achieved with a semi-rigid ankle brace 8. The same can be one in cases of lateral ankle sprains complicated by small nondisplaced fractures. In more severe injuries a short-term immobilization can be prescribed beforehand 8.
Further management includes physical therapy and a comprehensive rehabilitation with early motion or movement exercises, followed by strengthening exercises, balance training and endurance and agility exercises in the later stages, emphasizing proprioception as well as neuromuscular and postural control 5.
Surgical treatment plays a minor role in the treatment of acute ankle sprains and includes arthroscopy and/or ligament repair or reconstruction e.g in chronic cases, more severe cases in athletes or extensive ligamentous injuries. The indication is recommended to be done on an individual basis and should also be focussed on preventing repetitive sprains 8.
A major sequel of lateral ankle sprains in particular if repetitive is chronic ankle instability 1-3.
More than half of the patients have still residual symptoms between 6 weeks and 18 months 5,10 and up to 30% report pain on activity 2.5 to 5 years after the acute event 9. Up to 5% of athletes sustaining an ankle sprain have to change and up to 4% to stop their sportive activities 3. In non-athletes, up to 6% are not able to continue their previous occupation and a further 15% need additional support to continue it 1. Short-term prognostic factors include weight-bearing status and injury grade, medium-term pain, weight-bearing and a functional activity score 6. There are also reports, which found that MRI is an independent predictor 9.
Differential diagnosis
Practical points
In the case of combined anterior talofibular and calcaneofibular ligament injury, special scrutiny should be placed on the deltoid ligament to look out for additional deltoid ligament injury as well as on a possible associated subtalar injury.