Chronic ankle instability refers to an unstable ankle joint due to repetitive occasions of ankle instability with concomitant symptoms persisting for longer than one year after an initial ankle injury.
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Epidemiology
Ankle injuries are common and not only in the context of sports injuries 1-4. They have a high recurrence rate and the risk of developing chronic ankle instability after estimates sustaining a first-time ankle sprain are considered as high as up to 40% 1,2.
Risk factors
Risk factors for developing chronic ankle instability include the following 1-3:
- recurrent lateral ankle sprains
- multi-ligament injuries
- subtalar joint variants or pathologies
- impaired proprioception or postural balance
- first-time ankle sprain at a younger age
- self-reported functional deficit 6 months after the first ankle sprain
Associations
Chronic ankle instability is associated with the following clinical conditions 1-6:
- pathologic ligament laxity
-
tibiotalar joint pathologies
- chondral or osteochondral injury
- synovial inflammation and/or ankle impingement
- positional errors of the fibula, restricted dorsiflexion
- degenerative changes e.g. osteoarthritis
- subtalar joint pathologies
- decelerated proprioception
- neuromuscular, postural and strength deficiencies
Diagnosis
The diagnosis of chronic ankle instability is established clinically 5,6.
Diagnostic criteria
According to a position statement of the International Ankle Consortium criteria should include the following 5:
- ankle sprain with typical symptoms and interruption of physical activity more than 12 months prior
- and one or more of the following:
- recurrent episodes of ankle sprains
- regular occurrence of unforeseeable and uncontrolled incidents of excessive inversion of the rearfoot also termed as ‘giving way’
- subjective perception of ankle joint instability during activities of daily living or sports
- confirmation of self-reported instability with approved clinical questionnaires
Clinical presentation
The patient history will characteristically reveal at least one ankle sprain with typical symptoms and interruption of physical activity more than 12 months prior followed by a history of either regular occurrence of unforeseeable and uncontrolled incidents of excessive inversion of the rearfoot, also termed as ‘giving way’, the subjective perception of ankle joint instability during activities of daily living or sports or recurrent ankle sprains 5,6.
Approved clinical questionnaires such as the ankle instability instrument or Cumberland ankle instability tool will typically confirm the self-reported instability 6-8.
Complications
Pathology
Etiology
Traditionally described etiologies of chronic ankle instability included mechanical and functional instability.
A more modern conceptual model suggests a primary injury usually involving the anterior talofibular and/or calcaneofibular ligament as an important cause for the development of chronic ankle instability and one or more additional possible causative factors. These include pathomechanical impairments such as ligament laxity, kinematic restrictions, secondary tissue injury or tissue adaptations as well as sensory-perceptual and motor behavioral impairments, which include diminished somatosensation, perceived instability, altered reflexes, neuromuscular inhibition, muscle weakness, balance deficits and others. Furthermore, personal and environmental factors play a role in the development of chronic ankle instability 3-5.
Radiographic features
Imaging is important in the assessment of primary and secondary tissue injury, which includes ligament injury and concomitant osseous, chondral or tendinous injuries. It can provide additional information in respect to the pathomechanical or structural impairments e.g. ankle impingement.
Plain radiograph
Increased anterior translation of the talus can be assessed by stress radiographs. They have high specificity but low sensitivity and are only of diagnostic value if positive 9,10.
Ultrasound
Ultrasound can depict the anterior talofibular and calcaneofibular ligaments. In addition, their laxity can be assessed with stress sonography, which was found to be significantly increased in patients with ankle instability compared to normal individuals 9-11.
MRI
MRI has high specificity and positive predictive value in the detection of anterior talofibular ligament injury as well as calcaneofibular ligament injury.
Furthermore, it can show associated injuries and/or articular pathologies which can cause ankle pain despite lateral ankle ligament repair such as deltoid ligament injury, syndesmotic injury, peroneal or flexor tendon injury as well as chondral or osteochondral lesions, intraarticular loose bodies tibiotalar spurs or the different forms of ankle impingement 9,10,12.
Due to these broad diagnostic possibilities, MRI is routinely recommended for surgical planning in the setting of chronic ankle instability despite its low sensitivity 12.
Typical MRI features of a ligament injury include torn or absence of the ligament, wavy or irregular contours, thickening and or increased signal in T2 weighted images 13.
Radiology report
The radiological report for the evaluation of chronic ankle instability should include a description of the following:
- ligamentous injuries
- possible concomitant chondral or osteochondral injury
- intra-articular loose bodies
- signs of ankle impingement
- concomitant syndesmotic injury
- signs of sinus tarsi syndrome
- injuries of the peroneal and flexor tendons
Treatment and prognosis
Even with chronic ankle instability, a minimal period of 3-6 months of conservative management should be considered involving a comprehensive rehabilitation program including physical therapy early motion or movement exercises, strengthening exercises, balance training and endurance and agility exercises as well as training emphasizing proprioception, neuromuscular and postural control 11,13,14.
If conservative management fails and/or in case of more severe concomitant injuries, such as chondral or osteochondral injury, intra-articular loose bodies and ankle impingement surgery can be considered and includes ankle arthroscopy and open surgical approaches.
Arthroscopy is done to confirm imaging findings of one part and to remove intra-articular loose bodies or repair any collateral injury such as chondral injuries, synovial hyperplasia or pinched in ligament stumps causing ankle impingement 14.
Open surgical approaches include direct ligament repair (e.g. the Broström-Gould repair) in patients with mechanical instability or reconstructive measures in cases of poor ligament quality or generalized ligament laxity 11. More severe injuries such as osteochondral fractures or osteonecrosis might also require open surgical approaches.
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