Orthopaedic Surgery - Ankle Instability

Basics

Chronic ankle instability usually develops after recurrent ankle sprains, most commonly caused by inversion of a plantarflexed ankle. Repeated injury can lead to persistent pain, recurrent episodes of giving way, and loss of confidence in the ankle during walking or athletic activity.

Ankle instability is broadly divided into functional instability and true mechanical instability.

Functional instability occurs when the patient experiences a subjective sensation that the ankle is unstable despite the absence of major ligamentous laxity. Pain, impaired proprioception, delayed neuromuscular responses, and weakness may contribute to the feeling that the ankle is “giving way.”

Mechanical instability is caused by structural insufficiency of the stabilizing ligaments. Physiologic joint motion is exceeded, and examination may demonstrate abnormal laxity with a positive anterior drawer test or talar tilt test.

General Prevention

Appropriate treatment of the initial ankle sprain is important in reducing the likelihood of developing chronic instability.

Early management should include activity modification, appropriate bracing, and a structured functional rehabilitation program.

Rehabilitation should continue until range of motion, strength, balance, proprioception, and functional performance have returned to satisfactory levels.

Epidemiology

Ankle sprains are extremely common athletic injuries and may account for as much as 40% of all sports-related injuries.

Approximately 27,000 ankle sprains occur each day in the United States.

Following an inversion injury of the lateral ankle ligaments, symptomatic chronic ankle instability may develop in up to approximately 20% of patients.

Prevalence

Chronic ankle instability is particularly common in athletes participating in sports that require repeated cutting, jumping, landing, and rapid changes in direction.

It is frequently encountered among soccer and basketball players.

Risk Factors

The most important risk factor is a previous ankle sprain.

Once an ankle has been injured, impaired proprioception, residual ligamentous laxity, weakness, and inadequate rehabilitation increase the likelihood of further sprains.

Other risk factors include connective-tissue disorders and a cavovarus foot alignment, which places the ankle in a mechanically vulnerable position for recurrent inversion injury.

Etiology of Functional Instability

Functional instability is multifactorial.

Neurologic factors include impaired proprioception, protective reflexes, and muscle reaction time.

Muscular contributors include deficits in strength, power, and endurance, especially involving the peroneal muscles.

Mechanical factors may coexist, particularly residual laxity of the lateral ligament complex.

These abnormalities can combine to produce recurrent instability even when gross mechanical laxity is not prominent.

Sequence of Lateral Ligament Injury

An inversion ankle sprain may produce sequential disruption of the lateral stabilizing structures.

The anterolateral joint capsule is injured first, followed commonly by the anterior talofibular ligament (ATFL).

With increasing injury severity, the calcaneofibular ligament (CFL) may also tear.

The posterior talofibular ligament is considerably stronger and is rarely disrupted except in severe injuries such as ankle dislocation.

Anterior Talofibular Ligament

The ATFL is the most frequently injured ligament of the ankle.

It is the primary restraint to inversion when the ankle is in plantarflexion.

The ligament is particularly vulnerable when inversion is combined with plantarflexion and internal rotation.

Anatomically, the ATFL arises approximately 1 cm proximal to the tip of the lateral malleolus and travels anteriorly toward its insertion on the talus.

It inserts approximately 18 mm superior to the subtalar joint, runs roughly perpendicular to the fibula, and is closely associated with the ankle joint capsule.

The ligament measures approximately 7 mm in width and 10 mm in length.

Calcaneofibular Ligament

The CFL contributes to stability of both the ankle and subtalar joints.

It is particularly important in resisting inversion when the ankle is dorsiflexed.

The ligament may tear when a dorsiflexed ankle is subjected to excessive inversion.

It originates near the ATFL, approximately 8 mm proximal to the tip of the fibula, and passes posteriorly and distally toward the calcaneus.

The CFL courses at approximately 130° relative to the fibula and inserts on the calcaneus approximately 13 mm distal to the subtalar joint.

It is extracapsular and contributes to the floor of the peroneal tendon sheath.

Posterior Talofibular Ligament

The posterior talofibular ligament is the strongest component of the lateral ankle ligament complex.

It is rarely injured during routine inversion sprains.

Disruption usually occurs only with severe trauma, particularly ankle dislocation.

Dynamic Stabilizers

The peroneal tendons and muscles are the major dynamic restraints against excessive ankle inversion.

Rapid activation of the peroneal muscles helps resist inversion forces and protects the lateral ankle ligaments.

Weakness, poor endurance, or delayed peroneal muscle response therefore contributes significantly to recurrent functional instability.

Associated Conditions

Chronic ankle instability may be associated with systemic connective-tissue disorders such as Ehlers-Danlos syndrome.

Generalized ligamentous laxity can make both conservative and surgical stabilization more difficult.

Diagnosis

The central diagnostic task is to differentiate functional instability from mechanical ligamentous instability.

Approximately 15–30% of patients following a simple ankle sprain may continue to experience residual symptoms, including peroneal weakness and functional instability.

Evaluation should therefore assess ligament integrity as well as neuromuscular and functional deficits.

Signs and Symptoms

Common symptoms include recurrent lateral ankle pain, intermittent swelling, and episodes of instability.

Patients frequently describe the ankle as suddenly “giving way,” particularly while walking on uneven ground, descending stairs, running, or participating in sports.

Symptoms may disappear completely between episodes.

History

A typical history includes repeated ankle sprains occurring with relatively minor trauma.

Patients may report repeated episodes of rolling the ankle during activities that previously would not have caused injury.

The subjective sensation of giving way is particularly characteristic.

Important historical factors include the number and severity of previous sprains, previous rehabilitation, use of braces, and the patient’s sporting and occupational demands.

Hindfoot Alignment

The hindfoot should be inspected while the patient is standing.

A cavovarus alignment predisposes the ankle to recurrent inversion and may contribute to failure of ligament reconstruction if left untreated.

Alignment should therefore be incorporated into both diagnosis and surgical planning.

Gait Assessment

The patient’s gait should be observed for protective patterns, abnormal loading, or recurrent inversion.

Walking, heel rise, and other functional maneuvers may reveal instability that is less obvious during a seated examination.

Neurovascular Examination

A complete neurovascular examination should be performed.

Patients with recurrent ankle sprains have an increased incidence of injury involving the superficial peroneal nerve.

Sensation, motor function, pulses, and capillary refill should therefore be assessed and documented.

Peroneal Tendons

The peroneal tendons should be palpated for tenderness, swelling, subluxation, or tearing.

Peroneal tendon pathology frequently accompanies chronic lateral ankle instability and can itself contribute to persistent lateral ankle pain.

Dynamic examination during active ankle movement may help identify tendon subluxation.

Range of Motion

Ankle range of motion should be measured, with particular attention to dorsiflexion.

Pain or crepitus during motion may suggest associated intra-articular cartilage injury or degenerative changes.

Restricted motion may also alter ankle mechanics and contribute to recurrent sprains.

Subtalar Joint Examination

Subtalar motion should be assessed carefully.

A rigid subtalar joint may raise suspicion for tarsal coalition or another structural abnormality.

Subtalar stability should also be examined because the CFL contributes to both ankle and subtalar stability.

Assessment of CFL Integrity

The CFL can be assessed with the ankle dorsiflexed while an inversion force is applied to the calcaneus.

Excessive medial translation or inversion of the calcaneus may indicate subtalar instability and CFL insufficiency.

Comparison with the opposite side is useful.

Anterior Drawer Test

The anterior drawer test primarily evaluates the integrity of the ATFL.

The ankle is placed near neutral, and an anterior or anterolateral force is applied to the heel while the distal tibia is stabilized.

Excessive forward translation of the talus relative to the tibia suggests ATFL insufficiency.

A difference of more than approximately 3 mm compared with the opposite side, or absolute anterior translation greater than approximately 10 mm, supports mechanical instability.

Stress radiography may be used to confirm abnormal translation.

Talar Tilt Test

The talar tilt test primarily evaluates the CFL.

The patient is usually seated with the ankle near neutral.

The examiner applies an inversion force to the hindfoot and midfoot as a single unit while preventing the forefoot from simply rotating medially.

A total talar tilt exceeding approximately 9–10°, or a difference of more than approximately 3° compared with the opposite side, suggests mechanical instability.

Stress mortise radiographs may be used for objective confirmation.

Imaging

Standard Radiographs

Initial imaging generally includes lateral and mortise radiographs of the ankle.

Radiographs are useful not only for assessing instability but also for identifying chronic post-traumatic abnormalities.

Possible findings include tibial marginal osteophytes, talar exostoses near the ATFL insertion, osteochondral lesions of the talus, and an os subfibulare.

Stress Radiographs

Stress radiographs can provide objective evidence of lateral ligament insufficiency.

Anterior talar translation is assessed on a lateral stress view.

The perpendicular distance between the posterior articular margin of the tibia and the talus is measured.

Anterior translation that is approximately 3–5 mm greater than the opposite side, or an absolute value around 10 mm or greater, supports mechanical instability.

Talar Tilt on Stress Imaging

Talar tilt is measured on a stress mortise radiograph.

The angle formed between the distal tibial articular surface and the talar dome is assessed during inversion stress.

A talar tilt approximately 3–5° greater than the opposite ankle, or an absolute tilt of about 10° or more, is consistent with mechanical lateral instability.

Differential Diagnosis

Chronic ankle pain may coexist with instability but may also arise from other disorders.

Important differential diagnoses include intra-articular fibrosis or synovitis, osteochondral lesions of the talus, peroneal tendon tears, and peroneal tendon subluxation.

A fracture of the lateral process of the talus should also be considered, particularly following a significant inversion injury.

Persistent symptoms after a supposedly uncomplicated ankle sprain should therefore prompt evaluation for associated pathology.

Treatment

General Measures

Initial treatment of chronic ankle instability is generally nonoperative.

Early symptomatic management may include the RICE protocol: rest, ice, compression, and elevation.

More importantly, treatment should address the functional deficits that contributed to recurrence.

A structured rehabilitation program is therefore the central component of conservative management.

Bracing

An ankle brace can provide external support while injured ligaments and neuromuscular control recover.

Patients with moderate or severe sprains may continue using a functional brace for up to approximately 6 months, particularly during athletic activity.

Bracing can reduce recurrent inversion episodes while allowing continued participation in rehabilitation.

Importance of Rehabilitation

Persistent lateral ankle pain and functional instability are frequently related to incomplete or inadequate rehabilitation after the original injury.

Simply allowing pain and swelling to settle without restoring strength, endurance, proprioception, and balance can leave the ankle vulnerable to repeated sprains.

A comprehensive rehabilitation program is therefore essential before surgery is considered.

Activity

Sports participation should be restricted until rehabilitation has been completed adequately.

The patient should regain near-normal strength, range of motion, balance, and confidence before returning to unrestricted athletic activity.

Sport-specific tasks such as running, cutting, pivoting, and jumping should be performed without pain or instability before full return.

Bracing During Return to Sport

Functional bracing or taping during return to athletics may reduce the risk of recurrent sprains.

Appropriately fitted braces generally do not cause a significant reduction in athletic performance.

Athletes with previous ankle sprains may therefore benefit from continued preventive bracing during high-risk activities.

Physical Therapy

Physical therapy should focus on several key areas.

Range-of-motion exercises help restore normal ankle mechanics.

Both concentric and eccentric strengthening should be performed, particularly for the peroneal muscles.

Endurance training is important because fatigue can delay protective muscle responses and increase the risk of recurrent inversion.

Proprioceptive Training

Proprioceptive retraining is a major component of rehabilitation.

Exercises may include single-leg balance, unstable-surface training, and tilt-board exercises.

Progressive balance challenges improve joint-position awareness and neuromuscular reaction time.

This is particularly important in patients with functional instability.

Indications for Surgery

Surgery may be considered when significant instability persists despite an adequate functional rehabilitation program.

Other indications include marked mechanical laxity, recurrent sprains during routine daily activity, and persistent instability during sports despite appropriate bracing or taping.

The procedure selected depends on ligament quality, hindfoot alignment, previous surgery, patient demands, and the presence of generalized ligamentous laxity.

Anatomic Repair

Anatomic ligament repair generally produces the best results when the native ligament tissue remains of good quality.

The objective is to restore the normal anatomy of the ATFL and, when necessary, the CFL.

Advantages include preservation of subtalar motion and preservation of the peroneal tendons, which remain available as important dynamic stabilizers.

Limitations of Primary Repair

Direct anatomic repair may be unsuitable when the local ligament tissue is severely attenuated or deficient.

Examples include patients with connective-tissue disorders such as Ehlers-Danlos syndrome, failed previous stabilization surgery, or very longstanding instability with poor-quality tissue.

Patients with more than approximately 10 years of instability may have substantial ligament attenuation that makes direct repair less reliable.

Broström Repair

The Broström procedure is an anatomic repair of the lateral ankle ligaments.

The attenuated or torn ATFL is shortened and directly repaired.

The CFL may also be imbricated or repaired when instability involves both ligaments.

The operation aims to restore native anatomy without sacrificing the peroneal tendons or restricting normal subtalar motion.

Gould Modification

The Gould modification reinforces the repaired lateral ligament complex.

After the ATFL and CFL are repaired or imbricated, the inferior extensor retinaculum is advanced and attached to the fibula.

This provides additional reinforcement and improves stability.

The combined Broström-Gould repair is widely regarded as the standard operative technique for chronic lateral ankle instability and has reported success rates of approximately 90%.

Ligament Reconstruction

Ligament reconstruction is considered when direct repair is unlikely to provide adequate stability.

Indications include poor-quality or severely attenuated ligaments, failed previous Broström repair, generalized connective-tissue laxity, and selected obese or high-demand patients.

Modern anatomic reconstruction uses tendon graft tissue to reproduce the normal orientation and function of the native ATFL and CFL.

Graft Reconstruction

Autograft or allograft tendon may be used to reconstruct deficient lateral ankle ligaments.

The objective is to reproduce the native ligament anatomy and provide sufficient strength while preserving ankle and subtalar motion.

This approach is particularly useful in revision surgery or when local ligament tissue is unsuitable for primary repair.

Nonanatomic Reconstructions

Older procedures such as the Chrisman-Snook and Evans reconstructions use tendon tissue in a nonanatomic fashion to stabilize the lateral ankle.

Although these procedures can provide stability, they may alter normal ankle and subtalar mechanics.

Potential disadvantages include loss of talocrural or subtalar motion and risk of injury or dysfunction involving the peroneal tendons or nearby nerves.

For this reason, modern anatomic repairs and reconstructions are generally preferred when feasible.

Hindfoot Realignment

Persistent hindfoot varus can place excessive stress on a repaired lateral ligament complex.

In selected patients with significant cavovarus or hindfoot varus alignment, a calcaneal osteotomy may be performed together with ligament repair or reconstruction.

Correcting the underlying alignment reduces recurrent inversion forces and may improve the durability of the stabilization procedure.

Postoperative Care

Following surgery, the ankle is commonly immobilized in a cast or splint with the hindfoot positioned in slight eversion.

Immobilization generally lasts approximately 2–6 weeks, depending on the procedure and surgeon preference.

The patient is then transitioned to a removable brace.

Postoperative Rehabilitation

Physical therapy is usually continued for approximately 3 months or longer.

Rehabilitation progresses from protected range of motion to strengthening, proprioceptive training, balance exercises, and functional activity.

A protective ankle brace is commonly recommended for at least 6 months, especially during athletic activity.

Prognosis

The overall success rate of surgery for chronic lateral ankle instability is high.

Both appropriately selected anatomic repairs and reconstructive procedures can provide substantial improvement in stability, pain, and function.

Anatomic repair is generally favored when adequate native ligament tissue is available because it preserves more normal joint mechanics.

Predictors of Poor Outcome

Several factors are associated with less favorable results after surgery.

These include symptoms lasting 10 years or longer, established ankle osteoarthritis, and generalized joint hypermobility.

Uncorrected hindfoot malalignment and associated intra-articular pathology may also contribute to persistent symptoms.

Complications

Complications tend to be more common after nonanatomic reconstruction procedures than after modern anatomic repair.

Potential complications include loss of subtalar or ankle motion, stiffness, recurrent instability, and persistent pain.

Nerve Injury

Injury to the superficial peroneal or sural nerve may occur during surgical exposure or reconstruction.

This may result in numbness, dysesthesia, or painful neuroma formation.

Careful surgical technique and knowledge of the regional anatomy help minimize this risk.

Tendon-Related Complications

Procedures that use tendon tissue for nonanatomic reconstruction may alter normal tendon function.

Tendons are biomechanically different from native ligaments and are generally stiffer with less strain before failure.

Using the peroneal tendons for reconstruction can also reduce their role as dynamic stabilizers of the ankle.

Modern anatomic techniques therefore attempt to preserve the peroneal tendons whenever possible.

Patient Monitoring

Patients should be followed to assess pain, recurrent giving-way episodes, ligament stability, ankle and subtalar motion, strength, proprioception, and return to activity.

After surgery, monitoring should also include wound healing, neurologic function, brace tolerance, and progression through rehabilitation.

Long-term assessment is particularly important in patients with hindfoot deformity, generalized ligamentous laxity, or associated ankle osteoarthritis.