knee traumatic injuries

• 4 main ligaments: 

  Medial collateral lig - intracapsular 

  Lateral collateral lig - intracapsular 

  Anterior cruciate lig - extracapsular 

  Posterior cruciate lig – extracapsular 

   

  2 menisci (stabilising structures) - intracapsular 
• Ligament avulsion – ligamentous attachment pulled off bone. More common in younger patients but less common in knee than ankle  

   
• OTTAWA rules for knee xray: 

  Over 55 

  Tenderness on the patella  

  Tenderness on head of fibula 

  Can't flex the knee to 90 degrees 

  Cant weight bear for 4 steps 

   

  Series of clinical decisions to reduce unessecary imaging 

  Relevant findings include points of bony tenderness, weight bearing > 4 steps (plus others) 

  Only applicable in first 7 days of injury  

  Weight bearing counts even if limping ++ (immediate and in ED) 

   
• Ligament injuries: ACL – anterior aspect of intercondylar area of tibia attaches to the posterior aspect of intercondylar area of femur 

   

  Rotation forcing the knee out of the desired plane of movement – usually a valgus position 

   

  Non-contact injury – rotation/valgus force with fixed foot most common  

  Contact injury – Direct blow with valgus collapse (more likely to injure more than one structure)

  72% non contact,  

  28 % contact (Boden et al 2000)  

  70% occur in athletic populations (Griffin et al 2000)  

  Up to 15% of elite athletes and 3% of amateur athletes  
• Higher incidence of ACL tear in females  

  Neuromuscular control: Interplay between neural and muscular systems in providing dynamic stability to a joint 

   

  Few factors: 

  Anatomical 

  Hormonal 

  Neuromuscular  
• Typical presentation:

  Audible Snap or Pop 

  Immediate Pain 

  Haemarthrosis <2hrs 

  Difficulty Walking / Running 

  Instability/ giving way
• 
  

  ACL diagnosis: look for the end feel 

  Ligament stress tests  

  Positive test: increased laxity and soft end feel  

  Suprapatellar swelling in the knee 
• Joint effusion: Fluid in supra-patella pouch = Intra-articular injury  

  More vascularity = More/earlier swelling  

  Blood/fat in fluid = Bony injury 
• Assessing swelling: 

  Large effusions can be easily visible  

   

  Can also use:  

  Patella tap - good for medium effusions  

  Patella sweep – better for small effusions  

   

  ACL prevents anterior tibial translation  
• Ligamentous stability: special tests 

  Ligament stress tests: Positive test: increased laxity and soft end feel 

   

  Test unaffected side first 

  Anterior drawer test  

  Lachman's test – more sensitive and specific  

  MRI is always needed to confirm diagnosis  

   
• post op rehab:

  0-6 weeks:

  wound care

  swelling management

  regaining range

  normalising gait

  basic strengthening
• 6-12 weeks:

  regain strength

  regain neuromuscular control

  work toward running
• 12+ weeks:

  plyometrics

  speed and agitily

  sports-specfic exercise
• ACL: Conservative vs surgical management: Increased risk of OA following knee injuries:  

  ACL rupture- 7 times likely to have a total knee replacement  

  Meniscal injury- 15 times more likely 
• PCL: less common than ACL as it is a thicker ligament  posteriorly on the tibial tuberosity of the back of the this prevents the tibia being pushed back or the femur sliding forwards  
• Typical presentation: Audible Snap or Pop  

  Retropatellar Pain  

  Possible haemarthrosis  

  Difficulty walking downhill  

  Posterior sag sign – gravity pulls the tibia down 
• Positive test: increases laxity and soft end feel 

   

  Special test: 

  Posterior drawer test 

  Sag sign 

  Needs MRI to confirm diagnosis 
• Collateral ligaments: extracapsular  

  MCL – resists valgus stress 

  LCL – resist varus stress  

  
  

  Pain is more on the side of the knee and localised and superficial 

  Could use a ultrasound to diagnose it 

  
  

   More severe laxity may need moreimmobilisation
• Meniscus: 

  Function: 

  Axial load --> hoop stress 

  Improves joint congruency 

  Joint stability 

  Shock absorption  
• Periphery - more vascularised with greater healing capacity  

  Bucket handle tears more likely to cause mechanical symptoms – usually a larger tear  

   

  Similar mechanism to ACL – and more up to 4 times more common  
• Initial symptoms:  

  • Something ‘goes’  

  • Swelling within 24 hours  

   

  Ongoing symptoms:  

  • Locking  

  • Swelling  

  • Instability  

  • Pain in end range flexion and/or extension 

   

  Special test: diagnosis 

   

  McMurray's test  
• Thessaly’s test  

  Single leg squat to 20°  

  Rotate patient  

  Positive: pain reproduced with rotation  

  PLUS: Joint line tenderness is common  
• Meniscal tears can occur without trauma and be asymptomatic - can be considered a sign of aging 

   
• ‘Unhappy triad of O’Donoghue’: Combination of MCL, ACL and medial meniscus injury  

  These structures share similar injury mechanisms  

  The deep fibres of MCL attach to the medial meniscus  

  Severe instability = suspect multi-structure injury 
• Patella Dislocation: 

  Lateral dislocation most common – due to shape of trochlear groove  

   

  Subluxations can occur even without trauma if person is hypermobile and/or has shallow trochlear groove (and may happen more easily with time)