Ankle Achilles Complex Examination
The Achilles tendon examination is fundamental to ankle assessment. Examiners expect you to perform Thompson's test correctly for rupture, use the Silfverskiold test to differentiate gastrocnemius from soleus tightness, and recognize the clinical features of tendinopathy including the "painful arc sign."
Quick Reference One-Pager
Anatomy
- Gastrocnemius: Crosses knee and ankle
- Soleus: Crosses ankle only
- Both join to form Achilles tendon
- Inserts on calcaneal tuberosity
- Poorest blood supply 2-6cm above insertion
Rupture Signs
- Thompson's test positive (no plantarflexion on squeeze)
- Palpable gap (may be masked by swelling)
- Increased passive dorsiflexion
- Inability to single heel raise
- History: sudden pop, felt kicked
Tendinopathy Signs
- Midsubstance swelling (2-6cm above insertion)
- Painful arc sign (moves with ankle)
- Tenderness on palpation
- Morning stiffness
- Royal London Hospital test
Key Tests
- Thompson's (Simmonds') test
- Silfverskiold test (gastrocnemius vs soleus)
- Single heel raise test
- Matles test (knee flexion angle)
Anatomy
Gastrocnemius-Soleus Complex
Gastrocnemius:
- Two heads: Medial (from medial femoral condyle), Lateral (from lateral femoral condyle)
- Crosses TWO joints (knee and ankle)
- Tight when knee extended
- Primary plantarflexor during running/jumping
Soleus:
- Deep to gastrocnemius
- Origin: Posterior tibia and fibula
- Crosses ONE joint (ankle only)
- Primary postural muscle (standing)
Achilles Tendon:
- Formed by confluence of gastrocnemius and soleus
- Longest and strongest tendon in body
- Inserts on posterior calcaneal tuberosity
- Blood supply: Poorest 2-6cm above insertion (watershed zone)
Clinical Importance of Dual Origin:
- Silfverskiold test differentiates gastrocnemius from soleus tightness
- Knee extended: Both gastrocnemius and soleus tightness limit dorsiflexion
- Knee flexed: Only soleus tightness limits dorsiflexion (gastrocnemius relaxed)
Achilles Rupture Examination
History
Classic Presentation:
- Sudden onset, often during push-off activity
- "Pop" or "snap" felt
- Felt like "kicked in the back of the leg"
- Unable to push off or walk normally
- Age typically 30-50 years (recreational athletes)
- May have prodromal Achilles symptoms (tendinopathy)
Rupture Tests
Special test
Thompson's Test (Simmonds' Test)
Achilles tendon rupture
Technique
- 1Patient prone, feet hanging over edge of bed
- 2Squeeze the calf muscle belly
- 3Observe for ankle plantarflexion
Positive Sign
No plantarflexion of ankle on calf squeeze (foot stays still)
Indicates
Achilles tendon rupture
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Thompson's Test False Negatives: A false negative (apparently normal Thompson's) can occur with:
- Partial rupture (some fibers intact)
- Intact plantaris tendon (rare)
- Delayed examination with healing
If clinical suspicion high despite equivocal Thompson's, obtain ultrasound or MRI.
Special test
Matles Test (Knee Flexion Test)
Achilles tendon rupture
Technique
- 1Patient prone, knees extended
- 2Ask patient to actively flex both knees to 90°
- 3Observe resting ankle position from the side
Positive Sign
Affected ankle falls into neutral or dorsiflexion (normal side stays plantarflexed)
Indicates
Achilles tendon rupture (loss of tendon tension)
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Special test
O'Brien Test (Needle Test)
Achilles tendon rupture (continuity test)
Technique
- 1Insert needle through skin into Achilles tendon (2-6cm above insertion)
- 2Passively dorsiflex ankle
Positive Sign
Needle does not move with ankle dorsiflexion
Indicates
Achilles tendon rupture (loss of continuity)
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Special test
Single Heel Raise Test
Functional Achilles/calf assessment
Technique
- 1Patient stands on affected leg only
- 2Ask patient to rise onto toes (heel off ground)
- 3Normal: Should be able to perform multiple times
Positive Sign
Unable to perform single heel raise or significantly weak
Indicates
Achilles rupture (complete) or significant tendinopathy/weakness
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Additional Signs
Rupture Findings
Inspection:
- Swelling and bruising around Achilles
- Loss of normal tendon contour
- Increased passive dorsiflexion (asymmetric)
Palpation:
- Palpable gap in tendon (may be filled with hematoma/swelling)
- Tenderness at rupture site (usually 2-6cm above insertion)
Note Location:
- Most ruptures occur 2-6cm above calcaneal insertion (watershed zone)
- Insertional ruptures are less common
Achilles Tendinopathy Examination
Types of Tendinopathy
Midsubstance Tendinopathy (Non-insertional):
- 2-6cm above insertion
- Most common in runners
- Fusiform swelling
- Painful arc sign positive
Insertional Tendinopathy:
- At calcaneal insertion
- Associated with Haglund's deformity
- Often bilateral
- Older, less active patients
Special test
Painful Arc Sign
Achilles tendinopathy (midsubstance)
Technique
- 1Palpate the area of maximal tenderness on Achilles
- 2Have patient actively dorsiflex and plantarflex ankle
- 3Observe if point of tenderness moves with ankle motion
Positive Sign
Tender swelling moves proximally with dorsiflexion, distally with plantarflexion
Indicates
Tendinopathy (pathology in tendon itself). If doesn't move = paratenon pathology
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Special test
Royal London Hospital Test
Achilles tendinopathy
Technique
- 1Palpate tender area of Achilles with ankle in relaxed position
- 2Maximally dorsiflex ankle
- 3Reassess tenderness
Positive Sign
Tenderness disappears or significantly decreases with dorsiflexion
Indicates
Achilles tendinopathy (fibers under tension are less tender)
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Gastrocnemius/Soleus Tightness
Special test
Silfverskiold Test
Differentiate gastrocnemius from soleus tightness
Technique
- 1Patient supine or prone, hindfoot in neutral (subtalar joint)
- 2Measure passive ankle dorsiflexion with KNEE EXTENDED
- 3Then measure dorsiflexion with KNEE FLEXED to 90°
- 4Normal: greater than 10° dorsiflexion in each position
Positive Sign
Limited dorsiflexion with knee extended that improves with knee flexion = isolated gastrocnemius tightness. Limited in BOTH positions = soleus or combined tightness
Indicates
Gastrocnemius tightness (most common) vs Soleus tightness. Critical for surgical planning (gastrocnemius release vs TAL)
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Silfverskiold Test Interpretation:
- Knee Extended
- Greater than 10° DF
- Knee Flexed
- Greater than 10° DF
- Diagnosis
- No equinus
- Knee Extended
- Less than 10° DF
- Knee Flexed
- Greater than 10° DF
- Diagnosis
- Isolated gastrocnemius
- Knee Extended
- Less than 10° DF
- Knee Flexed
- Less than 10° DF
- Diagnosis
- Soleus or combined
Clinical Relevance:
- Isolated gastrocnemius tightness → Gastrocnemius recession (Strayer/Baumann)
- Combined tightness → Achilles lengthening (TAL) or gastrosoleus recession
Differential Diagnosis
- presentation
- Sudden pop, unable to push off
- tests
- Thompson's +, gap palpable
- imaging
- Ultrasound/MRI confirms
- presentation
- Gradual onset, activity pain, stiffness
- tests
- Painful arc +, RLH test +
- imaging
- Ultrasound shows thickening
- presentation
- Superficial pain, crepitus
- tests
- Tenderness doesn't move with ankle
- imaging
- Ultrasound/MRI
- presentation
- Posterior heel pain
- tests
- Squeeze test at insertion
- imaging
- Bursa visible on MRI
- presentation
- Pump bump, shoe irritation
- tests
- Prominent posterosuperior calcaneus
- imaging
- Lateral X-ray
- presentation
- Sudden calf pain, tennis leg
- tests
- Thompson's NEGATIVE (Achilles intact)
- imaging
- Ultrasound/MRI
Summary Presentation
“45-year-old man felt sudden pop in calf while playing squash 2 days ago. Now unable to walk normally.”
Acute vs Chronic Rupture
- acute
- Clear history, recent injury
- chronic
- Vague history, weeks/months ago
- acute
- Clearly positive
- chronic
- May be equivocal (scar tissue)
- acute
- Palpable (may be filled with hematoma)
- chronic
- Filled with fibrous tissue
- acute
- Cannot plantarflex/heel raise
- chronic
- Weak plantarflexion possible
- acute
- Primary repair or conservative
- chronic
- Often needs reconstruction (FHL transfer, V-Y advancement)
Examiner Tips
Do
- Perform Thompson's test with patient prone
- Test single heel raise (functional test)
- Compare passive dorsiflexion both sides
- Use Silfverskiold to differentiate gastrocnemius/soleus
- Palpate for gap (rupture) or swelling (tendinopathy)
Don't
- Forget to compare with opposite side
- Miss the painful arc sign in tendinopathy
- Perform Thompson's incorrectly (must squeeze calf, not tendon)
- Forget insertional vs midsubstance pathology
- Miss plantaris rupture (similar symptoms, Thompson's negative)