Ankle Instability Examination
Chronic ankle instability examination focuses on lateral ligament assessment using the anterior drawer and talar tilt tests. Examiners expect you to know the anatomy of the lateral ligament complex (ATFL, CFL, PTFL), understand the difference between mechanical and functional instability, and recognize the importance of peroneal function.
Quick Reference One-Pager
Lateral Ligament Complex
- ATFL: Most commonly injured, resists inversion in plantarflexion
- CFL: Resists inversion in neutral/dorsiflexion
- PTFL: Strongest, rarely injured in isolation
Key Tests
- Anterior drawer (ATFL)
- Talar tilt (CFL + ATFL)
- Squeeze test (syndesmosis)
- External rotation stress (syndesmosis)
Types of Instability
- Mechanical: Abnormal laxity (positive tests)
- Functional: Giving way despite negative tests (proprioceptive deficit)
Associated Findings
- Peroneal weakness (eversion)
- Proprioceptive deficit
- Osteochondral lesion (talar dome)
- Peroneal tendon pathology
Anatomy
Lateral Ligament Complex
Anterior Talofibular Ligament (ATFL):
- Origin: Anterior lateral malleolus
- Insertion: Talar neck (anterior)
- Function: Resists anterior translation and inversion in plantarflexion
- Most commonly injured (85% of ankle sprains)
Calcaneofibular Ligament (CFL):
- Origin: Tip of lateral malleolus
- Insertion: Lateral calcaneus
- Function: Resists inversion in neutral and dorsiflexion
- Injured in more severe sprains (often with ATFL)
Posterior Talofibular Ligament (PTFL):
- Origin: Posterior lateral malleolus
- Insertion: Posterior talus
- Function: Resists posterior translation
- Strongest, rarely injured in isolation
Order of Injury: In lateral ankle sprains, ligaments tear in sequence:
- ATFL (first and most common)
- CFL (with more force)
- PTFL (only in complete dislocation)
Clinical Implication:
- ATFL tear alone = anterior drawer positive
- ATFL + CFL tear = anterior drawer AND talar tilt positive
Clinical Assessment
History Clues
Acute Sprain:
- Inversion mechanism
- Immediate swelling (lateral)
- Difficulty weight bearing
- "Popping" sensation
Chronic Instability:
- Recurrent giving way
- Multiple previous sprains
- Feeling of ankle "looseness"
- Pain with uneven ground
- May have clicking (osteochondral lesion)
Mechanical vs Functional:
- Mechanical: Abnormal joint laxity on testing
- Functional: Giving way with normal laxity (proprioceptive/neuromuscular deficit)
- Often combination of both
Inspection and Palpation
Observation
Standing:
- Hindfoot alignment (varus = predisposing factor)
- Coleman block test (if cavovarus)
- Muscle bulk (peroneal wasting)
Lying:
- Swelling location (lateral = ATFL/CFL, anteromedial = syndesmosis)
- Ecchymosis pattern
- Previous surgical scars
Palpation (Lateral):
- ATFL: Anterior to lateral malleolus
- CFL: Below and posterior to lateral malleolus
- Peroneal tendons
- Base of 5th metatarsal (avulsion fracture)
- Lateral process of talus
Palpation (Medial):
- Deltoid ligament
- Posterior tibial tendon
Palpation (Syndesmosis):
- Along anterior tibiofibular ligament (proximal to joint)
Lateral Instability Tests
Special test
Anterior Drawer Test
ATFL integrity
Technique
- 1Patient seated with knee flexed 90°, foot relaxed
- 2One hand stabilizes distal tibia/fibula anteriorly
- 3Other hand cups heel from behind
- 4Ankle in slight plantarflexion (10-20°)
- 5Draw talus anteriorly out of mortise
Positive Sign
Increased anterior translation compared to opposite side (greater than 3mm difference) or sulcus sign anterolaterally
Indicates
ATFL tear/laxity
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Anterior Drawer Tips:
- Plantarflexion relaxes the CFL and puts ATFL under primary stress
- Look for "suction sign" or sulcus anterolaterally
- Compare with opposite side (some physiological laxity is normal)
- Best performed with patient relaxed (muscle guarding reduces sensitivity)
Special test
Talar Tilt Test (Inversion Stress)
CFL and ATFL integrity
Technique
- 1Patient seated or supine, foot over edge
- 2Ankle in neutral position
- 3Stabilize tibia/fibula with one hand
- 4Grasp calcaneus and invert (tilt talus into varus)
Positive Sign
Increased talar tilt compared to opposite side (greater than 5° difference)
Indicates
CFL tear (often with ATFL). Tests calcaneofibular ligament primarily
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Special test
Lateral Stability at 45° Flexion
Differentiate ATFL vs CFL
Technique
- 1Perform talar tilt at 45° plantarflexion
- 2Then perform at neutral
- 3Compare laxity
Positive Sign
More tilt in plantarflexion = ATFL involved. More tilt in neutral = CFL involved
Indicates
Helps identify which ligaments are involved
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Syndesmotic Instability Tests
Special test
Squeeze Test
Syndesmotic (high ankle) sprain
Technique
- 1Compress tibia and fibula together at mid-calf level
- 2This stresses the syndesmosis distally
Positive Sign
Pain at the syndesmosis (distal tibiofibular joint)
Indicates
Syndesmotic ligament injury
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Special test
External Rotation Stress Test
Syndesmotic instability
Technique
- 1Patient seated, knee flexed 90°
- 2Stabilize tibia with one hand
- 3Hold foot and externally rotate
Positive Sign
Pain at syndesmosis with external rotation
Indicates
Syndesmotic injury (AITFL, posterior tibiofibular, interosseous membrane)
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Special test
Cotton Test (Fibular Translation)
Syndesmotic widening
Technique
- 1Patient supine, ankle in neutral
- 2Stabilize tibia
- 3Grasp fibula and translate medially/laterally
Positive Sign
Increased lateral translation of fibula
Indicates
Syndesmotic widening, gross instability
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Associated Assessment
Special test
Peroneal Strength Testing
Dynamic stabilizer function
Technique
- 1Test ankle eversion strength against resistance
- 2Test foot plantarflexion and eversion (peroneus longus)
- 3Observe for peroneal tendon subluxation
Positive Sign
Weakness of eversion
Indicates
Peroneal weakness contributes to functional instability
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Proprioception Testing
Balance Tests:
- Single leg stance (eyes open, then closed)
- Normal: Can balance for 30 seconds or more each
- Compare sides
Romberg Variant:
- Stand on affected leg with eyes closed
- Increased sway = proprioceptive deficit
Grading System
- ligament
- ATFL stretched
- instability
- None
- anterior_drawer
- Normal
- talar_tilt
- Normal
- ligament
- ATFL partial/complete tear
- instability
- Mild to moderate
- anterior_drawer
- Positive
- talar_tilt
- May be positive
- ligament
- ATFL + CFL complete tear
- instability
- Gross
- anterior_drawer
- Grossly positive
- talar_tilt
- Positive
Differential Diagnosis
- location
- Lateral
- tests
- Anterior drawer +, Talar tilt +
- imaging
- Stress X-rays, MRI
- location
- Anterolateral (higher)
- tests
- Squeeze +, ER stress +
- imaging
- Widened mortise on X-ray, MRI
- location
- Posterolateral
- tests
- Eversion weakness, subluxation
- imaging
- Ultrasound, MRI
- location
- Deep ankle pain
- tests
- May have clicking, effusion
- imaging
- MRI (talar dome)
- location
- Subtalar region
- tests
- Subtalar tilt positive
- imaging
- Stress views, CT
- location
- Anterolateral
- tests
- Tenderness in anterolateral gutter
- imaging
- MRI
Summary Presentation
“26-year-old netball player with recurrent ankle 'giving way' over 2 years since initial sprain.”
Lateral vs Syndesmotic Instability
- lateral
- Inversion, plantarflexion
- syndesmosis
- External rotation, dorsiflexion
- lateral
- Below/anterior to lateral malleolus
- syndesmosis
- Above ankle joint, anterolateral
- lateral
- Anterior drawer, Talar tilt
- syndesmosis
- Squeeze, External rotation stress
- lateral
- Usually faster
- syndesmosis
- Prolonged (2-3x longer)
- lateral
- May return quickly
- syndesmosis
- Extended absence
Examiner Tips
Do
- Test anterior drawer with slight plantarflexion
- Compare BOTH sides for all tests
- Assess for syndesmotic injury (different treatment)
- Test peroneal strength
- Check proprioception (functional component)
Don't
- Forget to differentiate mechanical from functional instability
- Miss syndesmotic injury (common exam question)
- Ignore hindfoot alignment
- Skip peroneal assessment
- Forget to mention potential osteochondral lesion