WEEK 2 - ACUTE LIGAMENTOUS INJURY - KNEE

Question 1

risk factors for common acute, high-energy knee injuries

Answer 1

Risk factors:

ACL recurrency

• 2nd ACLI in 14% of cases (141/914)
• 50% in contralateral knee
• Non-contact ACLI – 76.5%
• F = <25 years
• M = 26-45 year

Question 2

ACLI - MOI

Answer 2

Injury patterns:

• ACLI
  
  • partial tears (15%)
  • complete ruptures (85%)
• isolated injuries = 25%
• combined with meniscal, cartilagenous, or collateral ligaments (75%)

2 main sub groups:

• non-contact (NCACLI) = roughly 80%
• contact = 20%

Situational Patterns

• rapid deceleration for the purpose of:
  
  • defensive pressing
  • changing direction
  • unilateral landings
  • regaining balance after kicking

Question 3

PCL injuries - mechanisms

Answer 3

• Fall on the tibia or blow forcing the tibia backwards inrelation to the femur
  
  • direct blow to proximal tibia
  • Dashboard injury
• Forced knee hyperflexion injury with foot plantar flexed
  
  • Landing onto/sliding on knees
• Hyperextension
  
  • Complication of PLC (postero-lateral corner) injury

Question 4

screening for features of concern (red flags) related to acute, high-energy knee injuries - ACL/PCL - concomittent injuries

Answer 4

Important screening considerations:

• concurrent injuries:
  
  • For ACL:
    
    • Commonly not an isolated injury
    • Bony bruising
    • Fractures
      
      • Tibial spine avulsion
      • Postero-lateral tibial plateau injury
      • Segond fracture
    • Lateral meniscus injury
      
      • Compression, crush injury to posterior horn due to lateral compartment subluxation
    • O’Donoghue’s Triad (cluster)
      
      • MCL tear
      • Medial meniscus
      • ACL tear
• PCL:
  
  • Fractures
  • PLC
  • meniscus injury

Question 5

relevant assessments for high-energy knee injuries - ACL, PCL, PLC, MCL, LCL, Patella dislocation and fractures

Answer 5

’s

ACL

• Lachman’s
• Anterior drawer

PCL

• Posterior drawer
• sag test (90 degree hip flexion + crook lying position (90 deg knee flex)

PLC

• Passive external rotation recurvatum test

MCL

• valgus assessment

LCL

• varus assessmentv
  ### Patellar Dislocation
• effusion displacement ‘ Milk Test’

• Ottawa knee rules

Question 6

ACL tear diagnosis

Answer 6

• MOI consistent with ACL injury
• Mechanical Sx at moment of injury
  
  • Audible or perceived “crack/pop/snap”
    and/or
  • “Felt my knee go in and out”
• Usually carried off field
  
  • Initial intense pain can settle quickly and athlete may feel able to play on
• Rapid hot effusion
  
  • usually within 2 hours
    
    • a common feature
    • minimal effusion is less common but not uncommon
  • if haemoarthrosis present = 80% chance of ACL tear and most will be a complete rupture
    
    • joint aspiration can confirm

Question 7

PCL rupture: diagnosis

Answer 7

• Acutely, a similar “story” to ACLI
  
  • But look for differences in MOI
    ##
• Landing + hypextension = PLC injury +/- ACLI
  Hyperextension MOI
  Motion can rupture (layer by layer)
  1. Posterior capsule stretched ++ or torn
  2. Posterior capsule torn/ruptured +/- 1.
  
  1. I.e. PLC
     
     3. ACLI then (potentially)
     4. PCLI (partially-to-wholly)
• Rapid, “hot” effusion also possible
• Functional instability (sub-acute-chronic)
  
  • “Unstable”/apprehensive going down stairs/inclines

P/E

• Stability tests
• +ve “Sag/drop” tests
• Posterior drawer +ve
• Reverse Lachmans +’ve
• Negate ACLI

Question 8

Patellar dislocation Diagnosis

Answer 8

MOI’s:

1. Trauma: blow to medial aspect of patella + underlying anatomy often WNL
2. Powerful muscular contraction (quads) upon a semi-flexed knee whilst pivoting/COD maneuver +/- presence of underlying anatomic anomalies
   
   • quadricep attachment usually pulls the patella laterally to the mid-axis
     - Pathology = medial patella retinaculum and MPF ligaments usually torn
   • Instability can also be atraumatic
     - Resultant recurrent subluxation due to dysfunction of medial restraining structures and impaired quadriceps function common

History and MOI:

• Internal rotation of body upon a fixed tibia
• Patella typically dislocates laterally

Acute injury, rapid swelling

• Haemarthrosis common (important diff Dx from ACLI)

Tender medial patella

• MPFL (medial patellar femoral ligament) /retinaculum tear
• Apprehension with movement (sub-acute-chronic)
  
  • Apprehension/relocation test
• X-ray to exclude #
  š Osteochondral lesions very possible