Chronic Ankle Instability

1. What Is Chronic Ankle Instability? Causes and Symptoms

Chronic ankle instability (CAI) is a condition characterized by a patient being more than 12 months removed from their initial lateral ankle sprain (LAS). It is defined by a propensity for recurrent ankle sprains, frequent episodes or perceptions of the ankle giving way, and persistent symptoms such as pain, swelling, limited motion, weakness, and diminished self-reported function. CAI can also be described as residual symptoms of ankle instability and a feeling of the ankle "giving way" that lasts more than a year after the initial sprain. It has been estimated that up to 40% of individuals who experience a first-time LAS will develop CAI. Other estimates suggest that approximately 30% of people who sustain an ankle sprain will experience a recurrent sprain and residual symptoms that last for more than one year.

CAI is a heterogeneous injury where individual patients present with unique combinations of impairments. The updated model of CAI describes how primary tissue injury to the lateral ankle ligaments after an acute ankle sprain may lead to a collection of interrelated pathomechanical, sensory-perceptual, and motor-behavioral impairments that influence a patient's clinical outcome.

The understanding of ankle instability has evolved, starting with Freeman et al. in 1965 who coined the term functional instability. Functional instability was operationally defined as the disability patients describe when their foot tends to "give way" in the months and years after an initial ankle sprain. This concept later shifted to represent the sensori-motor cause of persistent injury, contrasting with mechanical instability.

Based on current understanding, ankle instability can be categorized as either mechanical or functional instability.

• Mechanical ankle instability refers to objective measurements of ligament laxity. This represents the mechanical instability described in earlier models of CAI and involves the loss of structural integrity of the lateral ankle ligaments, resulting in pathologic laxity of the talocrural joint and potentially the subtalar joint. Disruption of the anterior talofibular ligament (ATFL) is associated with increased anterior drawer, or translation, of the talus within the tibiofibular mortise. While an initial increase in laxity is often seen after acute LAS, some residual laxity is likely to remain in most patients, although some studies report a return towards pre-injury laxity over time.
• Functional ankle instability (FAI), also referred to as perceived instability, is a subjectively reported phenomenon. It is characterized by repetitive episodes of giving way or instability around the ankle during daily and sports activities, and/or recurrent symptomatic ankle sprains. Patients reporting perceived instability may or may not actually experience episodes of excessive ankle inversion. It is thought that patients with FAI have disturbed neuromuscular control of the ankle caused by damage to muscles, receptors, or nerves from the initial ankle inversion injury. Functional instability has been linked to sensorimotor deficits such as impairments in balance, joint position sense, muscle reaction time, peripheral nerve properties, muscle strength, and range of motion.

The updated model of CAI uses concepts from dynamic systems theory and the neuromatrix of pain theory to describe how primary injury leads to a collection of interrelated pathomechanical, sensory-perceptual, and motor-behavioral impairments. These impairments, along with personal and environmental factors, interact to produce the patient's clinical outcome.

2. Anatomy of the Unstable Ankle: Ligaments and Proprioception

Key Structures in Ankle Instability

• The majority of ankle sprains involve damage to the lateral ligaments of the ankle.
• The anterior talofibular ligament (ATFL) is the ligament most commonly injured during a lateral ankle sprain (LAS).
• In more severe ankle sprains, concurrent injury of the calcaneofibular ligament (CFL) is also present.
• The posterior talofibular ligament (PTFL) can also be involved in the most severe, Grade III sprains, although this is relatively uncommon in athletes.
• Beyond ligaments, ankle instability is also linked to proprioceptive nerve endings located in the capsule and ligaments of the foot and ankle. These nerve fibers are thought to subserve reflexes that help stabilize the foot during locomotion.

How Ligament Damage and Neuromuscular Control Perpetuate Instability

1. Primary Tissue Injury: For chronic ankle instability (CAI) to develop, an initial LAS must occur, typically caused by excessive inversion and internal rotation of the rearfoot on the tibia. This initial injury primarily affects the lateral ankle ligaments, most commonly the ATFL and potentially the CFL.
2. Mechanical Instability (Ligament Laxity): Damage to the lateral ankle ligaments results in a loss of their structural integrity. This leads to pathologic laxity of the talocrural joint, which is defined as mechanical instability in earlier models of CAI. Disruption of the ATFL is associated with increased anterior drawer (translation) of the talus within the tibiofibular mortise. While some initial increase in laxity is seen after an acute LAS, some residual laxity is likely to remain in most patients, although some studies report a return towards pre-injury laxity over time. This mechanical laxity can contribute to the ankle's tendency to "give way".
3. Proprioceptive Deficits (Sensorimotor Impairments): Ankle injury is believed to disrupt joint afferents located in the supporting ligaments. Damage to the ligamentous and articular proprioceptors during the initial injury, and possible nerve injury secondary to ligament injury, are hypothesized causes for diminished somatosensation in patients with CAI. These deficits may manifest as reduced joint position sense, which is a component of proprioception. Studies have shown that individuals with CAI may have less accurate active joint position sense, particularly at angles near maximal inversion. The inability to accurately sense the ankle joint's position, especially before foot contact, could increase the risk of recurrent sprains because the foot might contact the ground in a position that predisposes the ankle to move into supination.
4. Impaired Neuromuscular Control (Functional Instability): Damage to muscles, receptors, or nerves from the initial ankle inversion injury is thought to disturb neuromuscular control. This represents functional ankle instability (FAI), which is characterized by repetitive episodes of giving way or a perception of instability. Functional instability is a subjectively reported phenomenon. Functional instability has been linked to sensorimotor deficits including impairments in balance, joint position sense, muscle reaction time, peripheral nerve properties, muscle strength, and range of motion. The diminished somatosensation and muscle weakness, particularly in the evertor muscles, can lead to inappropriate foot positioning and inability to counteract forces that cause inversion, potentially leading to recurrent injury. Neuromuscular disorders such as proprioceptive deficits and muscle weakness may cause persistent instability.
5. Perpetuation of Instability: The updated model of CAI describes primary tissue injury leading to a collection of interrelated pathomechanical (like ligamentous laxity), sensory-perceptual (like diminished somatosensation and perceived instability), and motor-behavioral impairments (like muscle weakness and altered movement patterns). These impairments influence the patient's clinical outcome. Recurrent episodes of giving way and recurrent ankle sprains can lead to further secondary tissue damage, which in turn exacerbates existing impairments, creating a cycle that perpetuates instability. The combined action of diminished proprioception and evertor muscle weakness is suggested as a possible cause of recurrent sprains in the instability group.

3. Causes and Risk Factors for Chronic Ankle Instability

• Previous ankle sprains (especially poorly rehabilitated ones).
• Poor proprioception, weak peroneal muscles, or hip/core instability.
• High-risk activities: basketball, soccer, trail running.

4. Why Physiotherapy is Essential for Chronic Ankle Instability

Several factors contribute to the development and perpetuation of chronic ankle instability and increase the risk of experiencing an ankle that keeps giving way:

• Previous Ankle Sprains: A primary cause and major risk factor for developing CAI is a history of a previous lateral ankle sprain (LAS). Up to 40% of individuals who experience a first-time LAS will develop CAI. Other estimates suggest that approximately 30% of people who sustain an ankle sprain will experience a recurrent sprain and residual symptoms that last for more than one year. The high rate of recurrence is associated with inadequate rehabilitation and incomplete healing. A history of previous sprains is the most common risk factor for ankle sprains in sports.
• Poor Proprioception and Neuromuscular Deficits: Ankle injury is believed to disrupt joint afferents located in the supporting ligaments, leading to diminished somatosensation. This impaired sensation, including reduced joint position sense, is a component of proprioception. This inability to accurately sense the ankle's position may increase the risk of recurrent sprains. The tendency for ankle sprains to recur is widely believed to be due to a proprioceptive deficit caused by damage during the original trauma. Studies have shown that individuals with CAI may have less accurate active joint position sense at angles near maximal inversion. Proprioceptive deficits and muscle weakness are suggested as neuromuscular disorders that may cause persistent instability.
• Weak Peroneal (Evertor) Muscles: Many investigators have found a relationship between peroneal muscle weakness and chronically unstable ankles. Evertor muscles, which counteract inversion forces, are particularly noted as being weak in individuals with CAI. Subjects with CAI seemed to have less concentric and eccentric evertor muscle strength than healthy individuals. Weakness of the evertor muscles may contribute to the foot being more inverted during gait. The combined action of diminished proprioception and evertor muscle weakness is suggested as a possible cause of recurrent sprains in the instability group.
• Weakness in Proximal Muscles (Hip/Core): While the sources focus heavily on ankle-specific deficits, some also suggest that a decrease in the strength of muscles that cross more proximal joints, such as the knee and hip, may play a role in CAI. Studies have looked at hip strength deficits in individuals with CAI.
• Impaired Balance and Postural Control: Functional instability is linked to sensorimotor deficits including impairments in balance and joint position sense. Patients with functional ankle instability often demonstrate deficits in postural control.
• Secondary Tissue Damage: Repetitive episodes of giving way or recurrent ankle sprains can result in further insult to the lateral ankle ligaments (ATFL and CFL) and other tissues around the ankle complex. This further damage can exacerbate existing pathomechanical, sensory-perceptual, and motor-behavioral impairments, creating a cycle that perpetuates the condition.
• High-Risk Activities: Ankle sprains are among the most common injuries incurred during participation in sport and physical activity. They are the most frequent sports injury, particularly in sports with jumping, cutting, and lateral movements. Specific high-risk sports mentioned or implied include football (soccer), basketball, and collegiate sports in general. The mechanism of injury typically involves excessive inversion and internal rotation of the rearfoot on the tibia. Activities that challenge balance or involve uneven ground or rapid directional changes would inherently be higher risk, although specific examples like "trail running" are not explicitly named in the sources.

The updated model of CAI describes it as a heterogeneous injury where patients present with unique combinations of pathomechanical (e.g., ligament laxity), sensory-perceptual (e.g., diminished somatosensation, perceived instability), and motor-behavioral impairments (e.g., muscle weakness, altered movement patterns). These interacting impairments, along with personal and environmental factors, contribute to the patient's clinical outcome.

5. Prognosis: Can Chronic Ankle Instability Be Cured?

• CAI often requires ongoing management rather than a simple "cure" [implied by the definition of CAI lasting >12 months, the discussion of breaking a vicious cycle, and the description of copers]. The updated model of CAI describes it as a heterogeneous injury involving interrelated pathomechanical, sensory-perceptual, and motor-behavioral impairments that influence a patient's outcome. Repetitive episodes of giving way and recurrent sprains can lead to further secondary tissue damage, which can exacerbate existing impairments, creating a cycle that perpetuates instability. Therefore, management aims to interrupt this cycle and improve function.
• Conservative management, primarily exercise-based rehabilitation, is the first-line approach for CAI. Exercise programs are effective at improving functional performance for physically active individuals with functional instability and can reduce subjective instability. They can lead to improvements in postural control, joint position sense, and muscular strength.
• Improvements can be seen with consistent rehabilitation over a period of weeks to months. Progressive therapeutic exercise is recommended for a minimum of 4 weeks. Studies show that balance training, a common component of rehab, can improve functional ankle instability symptoms after as little as 6 weeks. Exercise-based interventions have shown positive effects in the short term, although it's noted that long-term follow-ups are important to determine if improvements are maintained.
• The goal of rehabilitation is to stabilize the unstable ankle and break the vicious cycle of recurrent sprains and subsequent loss of proprioception and muscle atrophy.
• A successful outcome is achieving the status of a "coper," defined as an individual who is more than 12 months removed from the initial sprain, has not incurred recurrent sprains, reports minimal or no symptoms, and perceives a full recovery. It's important to note that copers may still have some identifiable residual impairments, such as increased laxity, but these do not negatively affect their function or perception. Achieving a full recovery also implies being able to return to pre-injury levels of physical activity without symptoms.
• Severe cases that do not respond adequately to conservative management may require surgery. If a patient with CAI does not make a concerted effort at conservative management and still experiences issues, referral to a foot and ankle surgeon might be considered to determine if they are candidates for lateral ligament reconstruction.

In summary, while CAI is a chronic condition lasting over a year, it is typically managed effectively through conservative rehabilitation. Consistent exercise and therapy can lead to significant improvements in symptoms and function within weeks to months, aiming to stabilize the ankle and prevent recurrence. The ultimate goal is often to achieve functional recovery (coper status), which may involve ongoing management rather than a complete elimination of all underlying deficits, but allows a return to desired activity levels. Surgery is generally reserved for cases unresponsive to thorough conservative treatment.

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6. Physiotherapy Treatment for Chronic Ankle Instability

Physiotherapy Treatment for Chronic Ankle Instability

The updated model of CAI serves as a framework for the clinical assessment and rehabilitation of patients. A new paradigm for conservative management of CAI focuses on assessing and treating the specific deficits exhibited by individual patients. Rehabilitation typically involves a therapeutic exercise program aimed at improving somatosensation, muscle activation, and strength; restoring functional movement patterns; and reducing kinesiophobia. It includes exercises to restore normal range of motion (ROM), strength, and balance, with endurance and sport-specific tasks added as progress is made. Exercise-based interventions are considered effective for improving functional performance and reducing subjective instability in physically active individuals with functional ankle instability.

6.1. Biomechanical Assessment

A comprehensive biomechanical assessment is a crucial initial step in physiotherapy for CAI to identify patient-specific deficits. This involves evaluating the primary tissue injury and specific pathomechanical, sensory-perceptual, and motor-behavioral impairments.

• Evaluate Ligament Integrity and Laxity: Loss of integrity of the lateral ankle ligaments results in pathologic laxity. Disruption of the anterior talofibular ligament (ATFL) is associated with increased anterior drawer. This mechanical instability is typically assessed, and identifying it is part of determining the primary tissue injury. Some residual laxity is common after a lateral ankle sprain (LAS), but it may not negatively affect function in individuals who are classified as "copers".
• Evaluate Joint Mobility: Beyond ligamentous laxity, specific accessory joint motions can be limited, known as arthrokinematic restrictions. Restrictions in the anterior-to-posterior glide of the talus on the tibia are associated with limited osteokinematic dorsiflexion. Anterior displacement of the talus or distal fibula may also be associated with restricted glide. Arthrokinematic restrictions can also occur at the subtalar, midtarsal, and tarsometatarsal joints. It's important to assess both arthrokinematics and osteokinematics, with arthrokinematic restrictions assessed first as they can mask osteokinematic findings. Decreased dorsiflexion ROM can contribute to a more plantarflexed foot position during gait, reducing stability and increasing injury risk. The goal is to restore ROM to equal the uninvolved limb or to established normal values.
• Evaluate Movement Patterns: Patients with CAI often exhibit altered functional movement patterns. These alterations can include altered kinematics, kinetics, and muscle activity during activities like walking and running. Assessing movement patterns is part of identifying motor-behavioral impairments. Deficits in postural control are also common and evaluated through tests like the Balance Error Scoring System (BESS) and the Star Excursion Balance Test (SEBT), which assess static and dynamic balance.

6.2. Strengthening Exercises

Strength deficits, particularly in the ankle musculature, are potential contributing factors to CAI.

• 6.2.1. Peroneal Muscle Strengthening: Deficits in ankle strength, especially eversion concentric strength, have been consistently shown in patients with CAI. Weakness of the evertor muscles is hypothesized to contribute to the foot being more inverted during gait. Strength training, particularly of the peroneal muscles, is emphasized in rehabilitation. This type of training may help stabilize an unstable ankle and break the cycle of recurrent sprains and subsequent muscle atrophy. Strengthening exercises for the ankle musculature are implemented to address identified deficits. Common exercises include 4-way resistive band exercises and manual resistance exercises. Eccentric strengthening can involve walking on the toes, heels, outsides of the feet, and insides of the feet for an extended period. Strengthening programs can increase force production around the ankle joint and may improve joint position sense and lower extremity function.
• 6.2.2. Hip and Core Stability Work: Weakness has been identified in muscles proximal to the unstable ankle, including those at the knee and hip. It is hypothesized that decreased strength in these more proximal muscles may play a role in CAI. Therefore, assessing potential weakness in muscles crossing the ankle, knee, and hip joints is important, and strengthening exercises should address any identified deficits.

6.3. Proprioceptive and Balance Training

Patients with CAI have shown deficits in proprioception and neuromuscular control. Balance deficits are commonly observed.

• Balance training programs are effective interventions for CAI. They can decrease the incidence of ankle sprains and improve postural control. Proprioception training, alongside strength training, is considered important in rehabilitation.
• Balance deficits can be detected using tests like the BESS (static balance) and SEBT (dynamic balance). Static balance involves maintaining quiet unipedal stance. If static balance deficits are detected, static balance exercises, similar to those for acute sprains, should be implemented, progressing as the patient is able. Dynamic balance requires reaching in various directions while maintaining balance. If dynamic deficits are found, dynamic balance exercises are used.
• Specific balance training exercises mentioned include balance on foam, wobble boards, bosu, or ankle discs. Progressive therapeutic exercise, including balance training, is recommended for a minimum of 4 weeks. Balance training appears to have the greatest impact on self-reported function in patients with CAI. Examples of balance training exercises include single limb hops to stabilization and variations.

6.4. Neuromuscular Re-Education

Patients with CAI have impaired neuromuscular control. Rehabilitation aims to address sensorimotor and functional deficits and restore functional movement patterns. The assessment and treatment paradigm includes addressing deficits in functional activities such as walking, running, jumping, and cutting. These activities can be incorporated into therapeutic exercise programs. Rehabilitation emphasizes perception-action processes to help normalize altered movement patterns that may have developed.

6.5. Manual Therapy

Manual therapy can be part of a rehabilitation program. If tests reveal arthrokinematic restrictions, therapeutic techniques should be used to address both arthrokinematic and osteokinematic restrictions, including joint mobilizations (grade III or higher). Passive accessory joint mobilizations are specifically mentioned as beneficial for patients with arthrokinematic restrictions. Mobilization with movement techniques have also been shown to increase posterior talar glide and dorsiflexion in those with recurrent ankle sprains and should be considered. Joint mobilization has been shown to improve spatiotemporal postural control, range of motion, self-reported function, and dynamic balance in individuals with CAI.

6.6. Bracing and Taping

Ankle taping or bracing can be included in a rehabilitation approach during physical activity to address ankle laxity. During the acute phase, orthotics like an Aircast or walking boot may be used for partial immobilization and protection. Ankle bracing has been shown to be effective in decreasing the incidence of ankle sprains during athletic competition and can be used during both the rehabilitation process and upon return to play.

7. Preventing Recurrent Ankle Instability

Preventing recurrent ankle instability involves addressing underlying deficits and implementing strategies to improve stability during activity.

• 7.1. Consistent Strength and Balance Routines
• Strengthening exercises are a vital part of rehabilitation and play a role in preventing recurrence by addressing muscle weakness, which is a potential contributing factor to CAI. Deficits in ankle strength, particularly of the evertor muscles (like the peroneals), have been consistently shown in patients with CAI. Weakness of the evertors is hypothesized to contribute to the foot being in a more inverted position during gait. Strengthening programs, especially focusing on the peroneal muscles, are emphasized in rehabilitation. This training may help stabilize an unstable ankle and break the cycle of recurrent sprains and subsequent muscle atrophy. Common ankle strengthening exercises include 4-way resistive band exercises and manual resistance exercises. Eccentric strengthening, such as walking on the toes, heels, outsides of the feet, and insides of the feet, is also mentioned. For strength gains, exercises should be performed at least 3 days per week for at least 4 consecutive weeks. Deficits in muscle strength and altered active joint-position sense near maximal inversion are suggested as combined actions that contribute to recurrent sprains. Weakness in muscles proximal to the ankle, like those at the knee and hip, may also contribute to CAI, so assessing and addressing these deficits is important.
• Proprioceptive and balance training is considered crucial for preventing recurrent sprains. Patients with CAI often exhibit deficits in proprioception (awareness of joint position) and balance. A proprioceptive deficit may be a reason why ankle sprains recur in patients with CAI. Balance training programs are effective interventions for CAI. They can decrease the incidence of ankle sprains and improve postural control. Examples of balance training exercises include balancing on foam, wobble boards, bosu balls, or ankle discs. Balance training appears to have the greatest impact on self-reported function in patients with CAI. Progressive balance training, starting with static balance (e.g., single-leg stands) and progressing to dynamic activities, is part of rehabilitation programs.
• 7.2. Footwear and Orthotics
• The sources mention ankle taping or bracing can be included in a rehabilitation approach during physical activity to address ankle laxity. Ankle bracing has been shown to be effective in decreasing the incidence of ankle sprains during athletic competition and can be used during the rehabilitation process and upon return to play. The use of orthotics is mentioned in the context of assessing their effect on postural sway after a lateral ankle sprain, but specific recommendations on footwear or custom orthotics for long-term prevention of recurrence are not detailed in these sources.
• 7.3. Warm-Up and Sport-Specific Drills
• Rehabilitation programs for CAI aim to restore functional movement patterns, including activities like walking, running, jumping, and cutting. Addressing deficits in functional activities is part of the assessment and treatment paradigm. Neuromuscular re-education, which mimics sport or work demands, involves agility drills like lateral shuffles, zig-zag runs, and jump landings to help normalize potentially altered movement patterns that may have developed. These activities can be incorporated into therapeutic exercise programs. While specific warm-up routines are not detailed, the inclusion of functional and sport-specific drills suggests preparing the ankle for the demands of activity is part of a comprehensive approach that would likely include dynamic warm-up elements.

8. FAQs About Chronic Ankle Instability

• How is chronic instability different from a regular sprain?A regular ankle sprain is typically the initial injury, often caused by excessive inversion and internal rotation of the rearfoot on the tibia. Chronic ankle instability (CAI) is a condition that can develop after an initial lateral ankle sprain. It is characterized by symptoms that persist for more than 12 months after the initial injury. Individuals with CAI exhibit a propensity for recurrent ankle sprains, frequent episodes or perceptions of the ankle giving way, and ongoing symptoms like pain, swelling, limited motion, weakness, and diminished self-reported function. Functional ankle instability (FAI), a component of CAI, involves a subjective feeling of instability or repetitive giving-way episodes during daily or sports activities. In essence, while a regular sprain is the initial event, CAI is the long-term, often persistent, consequence in a significant percentage of individuals.
• Should I wear a brace forever?The sources indicate that ankle taping or bracing can be a part of a rehabilitation approach, particularly during physical activity, to help address ankle laxity. Ankle bracing has been shown to be effective in reducing the incidence of ankle sprains during athletic competition. It can be used during the rehabilitation process and upon return to play. It is not explicitly recommend to wear a brace "forever," being better suited as a supportive measure during specific activities and phases of recovery. The decision for long-term or indefinite bracing would likely depend on an individual's specific condition, activity level, and symptoms, and is not considered a universal recommendation.
• When is surgery needed for CAI?Patients with chronic ankle instability who do not respond favorably after making a concerted effort at conservative management may be considered for surgical intervention. In such cases, it is recommended that these patients be referred to a foot and ankle surgeon to evaluate if they are suitable candidates for lateral ligament reconstruction.

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