Thumb Examination
Thumb examination requires assessment of the three joints (CMC, MCP, IP), ligament stability (especially UCL), and tendon function. Examiners expect you to perform the thumb UCL stress test correctly, recognize CMC osteoarthritis patterns, and understand the significance of Stener lesion.
Quick Reference One-Pager
CMC (Base) OA
- Grind test positive
- Adduction contracture
- Square hand appearance
- First web space narrowing
UCL Injury
- Stress test in extension and 30° flexion
- Compare with contralateral
- Stener lesion: Palpable mass, needs surgery
- Greater than 30° laxity or no endpoint = complete
Tendon Assessment
- EPL: Lift thumb off table
- FPL: IP flexion
- APL/EPB: First compartment (de Quervain's)
Key Points
- UCL tears need stress X-ray
- CMC grind test highly specific
- Always check radial collateral too
- Stener lesion cannot heal without surgery
Anatomy
Thumb Anatomy
Joints:
- CMC (Carpometacarpal): Saddle joint, most mobile
- MCP (Metacarpophalangeal): Condyloid joint
- IP (Interphalangeal): Hinge joint
Key Ligaments:
- UCL (Ulnar Collateral Ligament): Primary restraint to radial deviation at MCP
- RCL (Radial Collateral Ligament): Less commonly injured
- Volar plate: Resists hyperextension
- Dorsal capsule: Resists flexion
Tendons:
- EPL (Extensor Pollicis Longus): Extends IP, third dorsal compartment
- EPB (Extensor Pollicis Brevis): Extends MCP, first compartment
- APL (Abductor Pollicis Longus): Abducts thumb, first compartment
- FPL (Flexor Pollicis Longus): Flexes IP
- Thenar muscles: APB, opponens, FPB superficial head (median nerve)
- Adductor pollicis: Ulnar nerve
Stener Lesion:
- UCL avulses and flips SUPERFICIAL to adductor aponeurosis
- Aponeurosis lies between ligament ends - cannot heal
- Palpable mass at ulnar MCP joint
- ALWAYS requires surgical repair
- Named after Bertil Stener (1962)
Clinical Presentation
CMC (Basal Joint) Osteoarthritis:
Demographics:
- Women more than men (10:1)
- Age greater than 50 years
- Bilateral common
Symptoms:
- Pain at thumb base with pinch/grip
- Difficulty opening jars
- Pain with key turning
- Progressive weakness
Signs:
- Square hand appearance
- Adduction contracture
- Prominence at base of thumb (subluxation)
- First web space narrowing
CMC Joint Examination
Special test
Grind Test (CMC Compression-Rotation)
CMC osteoarthritis
Technique
- 1Stabilize patient's wrist with one hand
- 2Grasp metacarpal with other hand
- 3Apply axial compression and rotation (grinding motion)
Positive Sign
Pain at CMC joint with crepitus
Indicates
CMC osteoarthritis - bone-on-bone contact causes pain
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Special test
Distraction Test
CMC joint assessment
Technique
- 1Apply axial distraction to thumb metacarpal
- 2Compare pain level with and without distraction
Positive Sign
Pain relieved with distraction
Indicates
CMC joint pathology (OA, synovitis) - distraction unloads joint
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
CMC Joint Assessment
Observation:
- Squaring at thumb base (dorsoradial subluxation)
- First web space contracture
- Thenar wasting (disuse)
Palpation:
- Tenderness at CMC joint
- Dorsal osteophytes
- Subluxation/instability
Range of Motion:
- Adduction/abduction
- Opposition
- Circumduction
Function:
- Pinch strength (compare with contralateral)
- Grip strength
- Key pinch, tip pinch, tripod pinch
UCL Injury Examination
Special test
UCL Stress Test (Valgus Stress)
Thumb UCL integrity
Technique
- 1Stabilize metacarpal with one hand
- 2Apply radial deviation stress to proximal phalanx
- 3Test in FULL EXTENSION and at 30° FLEXION
- 4Compare with contralateral thumb
Positive Sign
Greater than 30° of laxity OR greater than 15° difference from contralateral OR no firm endpoint
Indicates
Complete UCL rupture requiring surgical repair
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
UCL Testing Technique:
Extension Position:
- Tests accessory collateral ligament AND UCL proper
- If stable in extension, may have partial tear
30° Flexion:
- Relaxes accessory collateral and volar plate
- Isolates the UCL proper
- More sensitive for UCL tears
Criteria for Complete Tear:
- Greater than 30° total laxity
- Greater than 15° more than contralateral
- Absent firm endpoint
Always test both positions and compare sides!
Special test
Stener Lesion Palpation
Identify displaced UCL
Technique
- 1Palpate ulnar aspect of thumb MCP joint
- 2Feel for mass proximal to joint line
Positive Sign
Palpable mass (like a pea) at proximal aspect of MCP joint
Indicates
Stener lesion - UCL has displaced superficial to adductor aponeurosis, requires surgery
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Special test
RCL Stress Test
Radial collateral ligament integrity
Technique
- 1Stabilize metacarpal
- 2Apply ulnar deviation stress to proximal phalanx
- 3Test in extension and flexion
Positive Sign
Increased laxity compared to contralateral side
Indicates
RCL injury (less common than UCL)
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Tendon Examination
Extensor Tendons
EPL (Extensor Pollicis Longus):
- Test: Place palm flat on table, lift thumb toward ceiling
- Palpate tendon on ulnar side of anatomical snuffbox
- Rupture: Cannot extend IP joint (may occur post-distal radius fracture)
EPB (Extensor Pollicis Brevis):
- Extends MCP joint of thumb
- Part of first dorsal compartment
- Test: Extend MCP while resisting
APL (Abductor Pollicis Longus):
- Abducts thumb metacarpal
- Part of first dorsal compartment
- Forms radial border of snuffbox
Flexor Tendons
FPL (Flexor Pollicis Longus):
- Flexes IP joint
- Test: Hold MCP extended, flex IP against resistance
- AIN palsy: Weakness of FPL (part of "OK sign" assessment)
FPB (Flexor Pollicis Brevis):
- Flexes MCP joint
- Superficial head: Median nerve
- Deep head: Ulnar nerve
Special test
Finkelstein's Test
De Quervain's tenosynovitis (first compartment)
Technique
- 1Patient makes fist with thumb inside fingers
- 2Ulnar deviate the wrist passively
Positive Sign
Sharp pain at radial styloid (first dorsal compartment)
Indicates
De Quervain's tenosynovitis - stenosing tenosynovitis of APL and EPB
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Special test
Eichhoff's Test (Modified Finkelstein's)
De Quervain's tenosynovitis
Technique
- 1Patient actively makes fist over thumb
- 2Patient actively ulnar deviates wrist
Positive Sign
Pain at first dorsal compartment
Indicates
De Quervain's tenosynovitis (note: many false positives)
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Trigger Thumb Assessment
Trigger Thumb Examination
Palpation:
- Nodule at A1 pulley (volar, at MCP crease)
- Tenderness at A1 pulley
Active Movement:
- Ask patient to flex and extend thumb
- Observe for catching, clicking, or locking
- Note if triggering occurs with flexion or extension
Classification (Quinnell):
- Description
- Normal movement
- Description
- Uneven movement
- Description
- Actively correctable locking
- Description
- Passively correctable locking
- Description
- Fixed locked position
Pediatric Trigger Thumb:
- Usually presents with fixed flexion of IP joint
- Notta's nodule palpable
- May spontaneously resolve in first year
Differential Diagnosis
- location
- Base of thumb
- test
- Grind test
- keyFeature
- Square hand, web space contracture
- location
- Ulnar MCP
- test
- Valgus stress
- keyFeature
- Laxity greater than 30°, Stener lesion
- location
- Radial styloid
- test
- Finkelstein's
- keyFeature
- First compartment tenderness
- location
- A1 pulley (volar MCP)
- test
- Active flexion/extension
- keyFeature
- Clicking, nodule palpable
- location
- CMC joint
- test
- X-ray
- keyFeature
- Post-trauma, intra-articular fracture
- location
- Snuffbox
- test
- Snuffbox tenderness
- keyFeature
- FOOSH, pain with thumb loading
Summary Presentation
“24-year-old man fell while skiing 2 days ago and hit his thumb on the pole. He has pain and weakness gripping objects.”
Examiner Tips
Do
- Test UCL in both extension AND 30° flexion
- Compare with contralateral side (essential)
- Palpate for Stener lesion
- Perform grind test for CMC OA
- Test individual tendons (EPL, FPL)
Don't
- Forget to test at 30° MCP flexion
- Miss Stener lesion (surgical emergency)
- Confuse UCL with RCL
- Forget Finkelstein's for radial-sided pain
- Ignore associated fractures (request X-ray)