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Patella & Knee | Lower Extremity Trauma


  • the patella is a pulley, redirecting forces to the tibia
  • your first choice should never be a total patellectomy, as this results in a 33% extension strength loss
  • Classification based on pattern
    • non displaced
    • transverse – can be unstable, especially if gapped
    • proximal pole
    • distal pole
    • stellate
    • vertical – not very unstable
  • Conservative Treatment
    • displaced <2mm at the articular surface or gapped less than 3mm
    • immobilize in extension, but can weight bear
    • around 3 weeks you can start progressive range of motion
  • Surgical
    • if displaced, and unable to do a straight leg raise
    • The most biomechanically stable construct is cannulated screws with tension band wire
    • If a very comminuted distal or proximal pole, you can do a partial excision (partial patellectomy)
    • goal is early stable range of motion, but there is a degree of failure with some amount of extensor lag
    • hardware prominence is common complication
    • if you can’t do a straight leg raise, the extensor retinaculum is disrupted

Quad Tendon & Patellar Tendon

  • quad tendon ruptures more common in older population, patellar tendon in younger patients
  • if less than 50% involvement you can treat conservatively
  • if you see an x-ray where patella is very low or very high, you probably don’t need an MRI
  • if there is a question you can order an MRI

Patellar Dislocation

  • Most commonly dislocates laterally
  • usually the medial sided tissues give way (i.e MPFL rupture)
  • Usually the first dislocation you can treat nonoperatively, but for recurrent or grossly unstable patellar dislocation the correct treatment is MPFL reconstruction

Knee Dislocations

Screenshot-2017-01-29-10.15.59-350x398 Patella & Knee | Lower Extremity Trauma BOARD REVIEW Lower Extremity | TRAUMA TRAUMA

Lateral Radiograph of an Anterior Knee Dislocation

  • posterolateral direction is most common rotatory dislocation
    • this can result in button-holing of the medial femoral condyle through the medial soft tissues and injury to the posterolateral corner, lateral biceps, LCL, and peroneal nerve, as well as the popliteal vessels
  • ACL, PCL, medial and lateral collateral ligaments, menisci, cartilage, vasculature, nerves can all be damage
  • Direction of dislocation is classified according to the direction of the tibia
  • Posterior dislocations are associated most commonly with a popliteal artery injury
  • KD (Schenk) Classification of Knee Dislocations
    • KD-I: Single ligament injury (ACL or PCL)
    • KD-II: Double ligament injury (ACL and PCL)
    • KD-III: Triple ligament injury (*most common type)
      • KD-IIIM: Injury to ACL, PCL, and MCL
      • KD-IIIL: Injury to ACL, PCL, and LCL (+/- posterolateral corner)
    • KD-IV: 4 ligament injury (ACL, PCL, LCL/posterolateral corner, MCL/posteromedial corner)
    • KD-V: Multiligamentous injury with peri-articular fracture
  • Anytime you see a knee dislocation, or if you see a multiligamentous knee injury that is already reduced, you have to be concerned about a neurovascular injury
  • Physical exam is the first step
  • Ankle-Brachial Index
    • Ankle pressure over brachial pressure
    • if above 0.9, it can be observed
      • should not be sent home (admit overnight)
    • if below 0.9, it requires vascular consult
  • After reduction
    • can put in ex-fix, but most of the time only requires a brace
    • older literature suggested delayed reconstruction/surgery
    • however, newer literature suggests earlier surgery, and is trending toward supporting reconstruction
  • Peroneal n. injury
    • usually think about some type of tendon transfer down the road



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