Lateral Ankle Instability
ATFL and CFL Insufficiency
Ankle Sprain Grades
Critical Must-Knows
- ATFL: Weakest lateral ligament. Resists inversion in plantarflexion. Most commonly injured.
- CFL: Injured in severe sprains. Resists inversion in dorsiflexion. Crosses both ankle and subtalar joints.
- Anterior Drawer: Tests ATFL integrity. Compare to contralateral side.
- Talar Tilt: Tests CFL integrity. Performed in neutral dorsiflexion.
- Brostrom-Gould: Direct ATFL repair + inferior extensor retinaculum augmentation. Gold standard surgical treatment.
Examiner's Pearls
- "ATFL is weakest - always injured first (ACP order)
- "Anterior drawer tests ATFL, talar tilt tests CFL
- "Rehabilitation first - majority stabilize without surgery
- "Brostrom repair is gold standard (85-90% success)
- "Reconstruction for revision, heavy athletes, or generalized laxity
Critical Anatomy
Lateral ligament injury order: ATFL → CFL → PTFL (weakest to strongest).
- ATFL is weakest - injured with inversion in plantarflexion (most common mechanism).
- CFL is next - injured with greater force (inversion in dorsiflexion). Crosses ankle AND subtalar joints.
- PTFL is strongest - only injured in severe ankle dislocations.
- Remember: ACP = Anterior, Calcaneofibular, Posterior (weakest to strongest).
At a Glance Table
| Feature | Details |
|---|---|
| Definition | Chronic mechanical and/or functional instability of the lateral ankle complex |
| Epidemiology | 23,000 ankle sprains/day (US); 20-40% develop chronic instability |
| Key Ligaments | ATFL (most common), CFL, PTFL (rare) |
| Mechanism | Inversion injury, typically in plantarflexion |
| Key Exam | Anterior drawer (ATFL), Talar tilt (CFL) |
| First-Line Treatment | Rehabilitation: proprioceptive training + peroneal strengthening |
| Surgical Gold Standard | Brostrom-Gould repair (85-90% success) |
| Reconstruction Indications | Failed Brostrom, generalized ligamentous laxity, revision, heavy athletes |
Lateral Ligaments - ACP
Memory Hook:ACP = Anterior to Posterior = Weakest to Strongest. Like the alphabet, A comes first (injured first).
Stress Test Interpretation - ATE
Memory Hook:ATE my ankle! Know which ligament each stress test assesses.
SCAR - Lateral Ankle Surgery Complications
Memory Hook:SCAR reminds you of the main complications that can leave a mark on outcomes.
Overview/Epidemiology
Lateral ankle instability is the most common sports injury worldwide, affecting athletes across all sports and age groups.
Epidemiology
Incidence
- 23,000 ankle sprains per day in the United States
- 1 per 10,000 person-days in general population
- Up to 30% of all sporting injuries
- Most common in basketball, soccer, and volleyball
Natural History
- 20-40% of acute sprains develop chronic instability
- Risk factors: incomplete rehabilitation, ligamentous laxity
- 55% have residual symptoms at 6 months
- Recurrence rate without treatment: 70-80%
Demographics
- Peak incidence: 15-35 years (active population)
- Equal male:female ratio in general population
- Higher female incidence in specific sports
- Prior ankle sprain strongest risk factor
Types of Instability
- Mechanical Instability: Objective ligament laxity on stress testing
- Functional Instability: Subjective feeling of giving way despite normal stress tests
- Combined: Most patients have elements of both
Risk Factors for Chronic Instability
- Previous ankle sprain (strongest predictor)
- Incomplete or inadequate rehabilitation
- Generalized ligamentous laxity (Beighton score greater than 4)
- High-demand sports (basketball, soccer, netball)
- Hindfoot varus malalignment
- Cavovarus foot deformity
- Peroneal weakness or dysfunction
Pathophysiology and Mechanisms
Lateral Ankle Ligament Complex
The lateral ankle ligaments originate from the lateral malleolus and provide stability against inversion and anterior translation of the talus.
Lateral Ankle Ligaments - Detailed Anatomy
| Ligament | Origin | Insertion | Function | Injury Order |
|---|---|---|---|---|
| Anterior border of lateral malleolus | Talar neck (anterolateral) | Resists anterior translation + inversion in plantarflexion | 1st (weakest) | |
| Tip of lateral malleolus | Lateral calcaneus | Resists inversion in dorsiflexion; crosses ankle + subtalar | 2nd | |
| Medial surface of lateral malleolus | Posterior talus | Resists posterior translation; strongest ligament | 3rd (rarely injured) |
ATFL Anatomy (Most Important)
- Length: 20-25mm
- Width: 10-12mm
- Orientation: Horizontal in plantarflexion → becomes vertical in dorsiflexion
- Variants: 1-3 bands (2 bands most common)
- Strength: Weakest of the three (58-90N failure load)
CFL Anatomy
- Length: 20-25mm
- Crosses two joints: Ankle AND subtalar (unique feature)
- Orientation: 10-45° posterior to long axis of fibula
- Key relationship: Lies deep to peroneal tendons
- Clinical significance: CFL injury affects subtalar stability
Biomechanics of Injury
Injury Mechanism
The typical mechanism is inversion injury in plantarflexion:
- In plantarflexion, the narrower posterior talus sits in the mortise → less bony stability
- ATFL becomes the primary restraint → first to fail
- With continued force, CFL then fails
- PTFL only fails with severe trauma/dislocation
Dynamic Stabilizers
- Peroneus longus and brevis: Primary dynamic stabilizers
- Extensor digitorum longus: Secondary support
- Proprioceptive afferents: Critical for neuromuscular control
- Peroneal reaction time: Delayed in chronic instability
Classification Systems
Ankle Sprain Grading
Ankle Sprain Classification
| Grade | Pathology | Clinical Findings | Stability | Treatment |
|---|---|---|---|---|
| Microscopic tear, stretch injury | Mild swelling, tenderness | Stable | RICE, early mobilization | |
| Partial macroscopic tear | Moderate swelling, ecchymosis | Mild laxity | Brace 4-6 weeks, physio | |
| Complete rupture ATFL ± CFL | Severe swelling, ecchymosis | Frank instability | Brace, physio ± surgery |
Grade I and II injuries typically heal with conservative treatment. Grade III injuries may require surgical intervention if chronic instability develops.
Clinical Assessment
History
Key Questions:
- Initial injury: mechanism, treatment, rehabilitation
- Symptoms: giving way episodes, pain, swelling
- Functional limitation: sports, uneven ground, stairs
- Prior treatment: physiotherapy duration, bracing
- Red flags: locking (loose body), medial pain (deltoid), persistent swelling (OCD)
Physical Examination
Observation
- Swelling: lateral ankle, anterolateral gutter
- Ecchymosis: may indicate recent episode
- Hindfoot alignment: varus predisposes to lateral sprains
- Cavus foot: associated with instability
- Muscle wasting: peroneal atrophy suggests chronic injury
Inspection findings help assess the chronicity and severity of instability.
Investigations
Imaging Protocol
Standard Views
- Weight-bearing AP: Mortise alignment, OCD
- Mortise view: Lateral clear space
- Lateral: Talar dome, anterior impingement
Stress Radiographs (If Indicated)
- Anterior drawer stress: Greater than 10mm translation significant
- Talar tilt stress: Greater than 10° or greater than 5° vs. contralateral
- Useful for objective documentation
- Compare to contralateral side
Standard weight-bearing views are essential first-line imaging.
Associated Pathology to Exclude
| Condition | Frequency | Investigation | Clinical Significance |
|---|---|---|---|
| Osteochondral lesion (OCD) | 20-25% | MRI, CT | Address at surgery |
| Peroneal tendon pathology | 15-20% | MRI, ultrasound | May need concurrent repair |
| Anterior impingement | 10-15% | Lateral X-ray, MRI | Debride at arthroscopy |
| Syndesmosis injury | 5-10% | X-ray, MRI | Different treatment |
| Subtalar instability | Variable | Stress views | Consider reconstruction |
Management Algorithm
Treatment Decision Framework
First-Line for ALL Patients
Duration: 3-6 months minimum before considering surgery
Components:
-
Proprioceptive Training
- Wobble board exercises
- Single-leg stance progressions
- Sport-specific balance training
-
Peroneal Strengthening
- Resisted eversion exercises
- Theraband programs
- Functional strengthening
-
Ankle Bracing
- Semi-rigid brace for sport
- Lace-up brace for daily activities
- Taping for specific activities
-
Activity Modification
- Avoid uneven terrain initially
- Gradual return to sport
Success Rate: 70-80% of patients stabilize with rehabilitation alone.
Conservative treatment remains the cornerstone of management.
Treatment Algorithm Summary
- All patients: Rehabilitation first (3-6 months)
- Persistent symptoms: Brostrom-Gould repair
- Failed Brostrom/Generalized laxity/Heavy athlete: Anatomic reconstruction
- Revision surgery: Consider reconstruction with allograft
Surgical Technique
Brostrom-Gould Repair (Gold Standard)
Patient Positioning
- Position: Supine with bump under ipsilateral hip
- Tourniquet: High thigh (250-300mmHg)
- Leg position: Slight internal rotation for lateral access
Equipment
- Standard foot and ankle set
- Suture anchors (2.4-3.0mm)
- Non-absorbable braided suture
- Fluoroscopy (optional)
Approach
- Curvilinear incision over lateral malleolus
- Length: 4-6cm
- Identify and protect superficial peroneal nerve branches
Proper positioning and nerve protection are essential for successful repair.
Nerve at Risk
The superficial peroneal nerve is at risk with lateral ankle approaches. It typically crosses the surgical field 5-10cm proximal to the tip of the lateral malleolus. Always identify and protect this nerve to avoid sensory deficit.
Complications
Complications by Type
Intraoperative Complications
| Complication | Incidence | Prevention | Management |
|---|---|---|---|
| Superficial peroneal nerve injury | 2-5% | Careful dissection, identify before incision | Neurolysis, reassurance |
| Sural nerve injury | 1-2% | Posterior incision extension awareness | Reassurance (usually neuropraxia) |
| Inadequate tissue quality | 5-10% | Pre-op MRI assessment | Convert to reconstruction |
| Anchor pull-out | Rare | Proper technique, bone quality assessment | Re-anchor or transosseous sutures |
Nerve identification is the key to preventing intraoperative complications.
Postoperative Care
Rehabilitation Protocol
Immobilization Phase
Goals:
- Wound healing
- Pain and swelling control
- Prevent DVT
Protocol:
- Below-knee backslab or CAM boot
- Non-weight bearing or touch weight bearing
- Elevation, ice
- Ankle pumps (within splint if able)
Follow-up:
- Wound check at 10-14 days
- Remove sutures
- Transition to CAM boot
Early immobilization protects the healing repair.
Expected Outcomes
| Outcome Measure | Brostrom-Gould | Anatomic Reconstruction |
|---|---|---|
| Good/Excellent results | 85-90% | 80-90% |
| Return to sport | 85-95% | 80-90% |
| Recurrence rate | 5-10% | 5-15% |
| Time to sport | 4-6 months | 6-9 months |
Outcomes
Results by Treatment Type
Conservative Treatment
- 70-80% stabilize without surgery
- Best results with supervised physiotherapy
- Proprioceptive training key to success
- Peroneal strengthening essential
- Bracing for sport may be permanent
Brostrom-Gould Repair
- 85-90% good/excellent results
- Gold standard surgical treatment
- Preserves subtalar motion
- Lower revision rate than non-anatomic
- Return to sport: 4-6 months
Anatomic Reconstruction
- 80-90% good results
- Reserved for failures, laxity, heavy athletes
- Longer rehabilitation (6-9 months)
- Allograft reduces donor site morbidity
- Higher revision rate than primary Brostrom
Prognostic Factors
Favourable:
- Single ligament injury (ATFL only)
- Good tissue quality
- Normal hindfoot alignment
- Compliant patient
- Supervised rehabilitation
Unfavourable:
- Combined ATFL + CFL injury
- Generalized ligamentous laxity
- Hindfoot varus or cavovarus
- Associated OCD
- Poor compliance
Evidence Base
- Original description of direct ligament repair technique
- 85% good results at long-term follow-up
- Foundation for modern lateral ankle stabilization
- Added inferior extensor retinaculum augmentation
- Improved stability compared to Brostrom alone
- Provided additional proprioceptive input
- 78% of patients with chronic instability avoided surgery with rehabilitation
- Proprioceptive training was key component
- Peroneal strengthening improved outcomes
- Anatomic procedures superior to non-anatomic
- Brostrom-Gould most consistent outcomes
- Non-anatomic procedures restrict subtalar motion
- Comparable functional outcomes between approaches
- Arthroscopic allows treatment of associated pathology
- Similar complication rates
- Steeper learning curve for arthroscopic technique
Viva Scenarios
Practice these scenarios to excel in your viva examination
Recurrent Ankle Sprains in Athlete
"A 25-year-old basketball player presents with recurrent left ankle 'giving way' episodes despite 6 months of physiotherapy. He reports 3-4 episodes per month during games. Examination shows positive anterior drawer test compared to the contralateral side. What is your assessment and management plan?"
This is chronic lateral ankle instability with failed conservative treatment. The positive anterior drawer indicates ATFL insufficiency.
Assessment:
- Confirm rehabilitation was supervised and comprehensive
- Assess for CFL involvement (talar tilt test)
- Check hindfoot alignment (varus predisposes)
- Evaluate for generalized laxity (Beighton score)
- X-rays to exclude OCD, loose bodies
- MRI to assess ligament quality and associated pathology
Management:
I would offer Brostrom-Gould repair - direct ATFL repair with inferior extensor retinaculum augmentation. This is the gold standard with 85-90% good/excellent results.
Post-operative protocol: Protected weight bearing 4-6 weeks, CAM boot, then progressive rehabilitation with proprioceptive training. Return to sport expected at 4-6 months with ankle brace.
Failed Brostrom Repair
"A 30-year-old female netball player presents 18 months after a Brostrom repair with recurrent instability. She has hypermobile joints (Beighton score 6/9). Stress testing shows persistent ATFL laxity. How do you approach this case?"
This is a failed Brostrom repair in a patient with generalized ligamentous laxity. The high Beighton score suggests the native tissue repair has stretched out.
Assessment:
- Review operative notes from index procedure
- MRI to assess remaining ligament tissue and exclude other pathology
- Assess hindfoot alignment and exclude cavovarus
- Evaluate peroneal function
Management:
Given the generalized laxity and failed primary repair, I would recommend anatomic reconstruction rather than revision Brostrom. My preference would be semitendinosus allograft reconstruction to avoid donor site morbidity.
Key principles:
- Anatomic tunnel placement in fibula, talus, and calcaneus
- Graft tensioning in neutral dorsiflexion and eversion
- Interference screw or suture anchor fixation
- Recreate both ATFL and CFL
Rehabilitation is longer (6-9 months) with protected weight bearing for 6 weeks.
Acute Severe Ankle Sprain
"A 22-year-old soccer player sustains an inversion injury during a match. He has significant lateral swelling, ecchymosis, and tenderness over the ATFL. He cannot weight bear. Anterior drawer appears positive but is difficult to assess due to guarding. How do you manage this acute injury?"
This is an acute Grade III lateral ankle sprain with suspected complete ATFL rupture based on the mechanism, clinical findings, and apparent positive anterior drawer.
Acute Assessment:
- Ottawa Ankle Rules to determine need for X-ray
- X-ray to exclude fracture (lateral malleolus, base 5th metatarsal, anterior process calcaneus)
- Clinical exam under analgesia if needed for accurate assessment
- Assess syndesmosis (external rotation stress test)
Acute Management:
- RICE protocol: Rest, Ice, Compression, Elevation
- Functional bracing: Semi-rigid or lace-up ankle brace
- Weight bearing as tolerated with crutches
- Early mobilization: Begin ROM exercises within pain tolerance
Rehabilitation (Critical):
- Supervised physiotherapy starting early
- Proprioceptive training from week 2
- Peroneal strengthening program
- Sport-specific training before return
Prognosis: 80% of acute sprains heal well with functional treatment. 20-40% may develop chronic instability requiring further intervention.
MCQ Practice Points
MCQ: Weakest Lateral Ligament
Q: Which lateral ankle ligament is injured first during an inversion injury?
A: The ATFL (anterior talofibular ligament) is the weakest and most commonly injured. It is injured with inversion in plantarflexion - the most common ankle sprain mechanism. Remember ACP order: Anterior → Calcaneofibular → Posterior (weakest to strongest).
MCQ: Stress Test Interpretation
Q: A patient has a positive talar tilt test but negative anterior drawer. Which ligament is injured?
A: The CFL (calcaneofibular ligament) is injured. The talar tilt test assesses CFL integrity (inversion stress in dorsiflexion), while the anterior drawer tests ATFL. This pattern is unusual as ATFL is typically injured first, so consider other pathology.
MCQ: Gould Modification
Q: What does the Gould modification add to the original Brostrom repair?
A: The Gould modification adds augmentation with the inferior extensor retinaculum (IER). The IER is advanced over the ATFL repair and anchored to the fibula, providing additional restraint and improved proprioceptive input. This is now standard with all Brostrom repairs.
MCQ: Reconstruction Indications
Q: When is anatomic reconstruction preferred over Brostrom repair for lateral ankle instability?
A: Reconstruction is indicated for: (1) Failed Brostrom repair, (2) Generalized ligamentous laxity (Beighton score greater than 4), (3) Heavy/high-demand athletes, and (4) Poor quality native tissue. These patients have higher failure rates with direct repair.
MCQ: CFL Unique Feature
Q: What is unique about the calcaneofibular ligament compared to other lateral ankle ligaments?
A: The CFL crosses two joints - both the ankle joint AND the subtalar joint. This means CFL injury affects subtalar stability as well as ankle stability. The ATFL and PTFL only cross the ankle joint.
Australian Context
Australian Guidelines and Practice
Sports Medicine Australia (SMA) Guidelines:
- Functional treatment recommended for acute ankle sprains
- Immobilization reserved for Grade III injuries or non-compliance
- Supervised rehabilitation superior to unsupervised
- Return to sport based on functional criteria, not time alone
Referral Pathways
When to Refer to Orthopaedic Surgeon:
- Failed 3-6 months of supervised rehabilitation
- Recurrent instability affecting function or sport
- Associated pathology (OCD, syndesmosis injury)
- Elite athlete with mechanical instability
When to Refer to Sports Physician:
- Initial management of acute sprains
- Supervision of rehabilitation programs
- Assessment of return to sport readiness
Australian Epidemiology
- Ankle sprains account for 15-20% of sports injuries in Australia
- Higher incidence in netball (most common sport injury in women)
- Football codes (AFL, NRL, Rugby Union) have significant ankle injury burden
- Economic cost: Significant healthcare and lost productivity burden
Physiotherapy Standards (Australian Physiotherapy Association)
Rehabilitation Components:
- Early Phase: Pain management, protected mobility
- Middle Phase: ROM, strengthening, proprioception
- Late Phase: Sport-specific training, return to play assessment
- Maintenance: Ongoing proprioceptive work, bracing for sport
LATERAL ANKLE INSTABILITY
High-Yield Exam Summary
ANATOMY - ACP
- •ATFL: Weakest, injured first, resists inversion in plantarflexion
- •CFL: Crosses ankle AND subtalar, injured second
- •PTFL: Strongest, only injured in dislocations
- •ACP order = Anterior to Posterior = Weakest to Strongest
EXAMINATION
- •Anterior drawer = ATFL (anterior translation)
- •Talar tilt = CFL (inversion in dorsiflexion)
- •External rotation = Syndesmosis (NOT lateral ligaments)
- •Always compare to contralateral side
TREATMENT ALGORITHM
- •FIRST: Rehabilitation 3-6 months (majority stabilize)
- •SECOND: Brostrom-Gould repair (85-90% success)
- •THIRD: Reconstruction if failed Brostrom/laxity/heavy athlete
- •Gould modification = IER augmentation (always do this)
KEY NUMBERS
- •20-40%: Acute sprains → chronic instability
- •70-80%: Stabilize with rehabilitation alone
- •85-90%: Good results with Brostrom-Gould
- •4-6 months: Return to sport after Brostrom