Knee radiograph (an approach)

Check for an effusion on the lateral:

  • draw a line down the lateral margin of the lateral femoral condyle
  • if > 5 mm tibia is observed outside the line, think tibial plateau fracture
  • carefully look for a proximal tibial fracture
  • pay particular attention to:
    • tibial spine: avulsion
    • lateral tibial plateau: small avulsion (Segond fracture)
    • areas of increased density may point to underlying fracture
    • medial epicondyle: don't overcall calcification adjacent to the medial femoral epicondyle (Pellegrini-Stieda lesion)
  • fractures are usually easy to spot
  • don't call a bipartite patella a fracture: well-corticated unfused center at the superolateral pole
  • check for patella tendon disruption
    • patella tendon: inferior pole of patella to tibial tuberosity
    • patella tendon length = patella length ± 20%
  • fat and blood from bone marrow collect in suprapatellar bursa
  • a fat-fluid level may be the only sign of intra-articular fracture
  • associated with tibial plateau or distal femoral fractures
  • more: lipohemarthrosis
  • 80% involve the lateral plateau
  • fall from height or car bumper impact
  • associated significant cruciate and medial collateral ligament damage
  • more: tibial plateau fracture
  • avulsion fracture; bony fragment adjacent to lateral tibial plateau
  • internal rotation and varus stress; falls or sports
  • 75% associated with anterior cruciate ligament injury
  • more: Segond fracture
  • typically avulsion fracture of tibial attachment of anterior cruciate ligament
  • mechanism: rapid deceleration or hyperextension of the knee
  • most common in adolescents
  • more: intercondylar eminence fracture
  • majority transverse, also vertical or comminuted
  • direct blunt force or violent contraction of quadriceps
  • oblique or skyline views will confirm fractures
  • more: patella fracture
  • 6% of all femur fractures
  • bimodal distribution
  • high energy blunt trauma; falls in elderly
  • more: distal femoral fracture
  • typically occur with lateral tibial plateau fractures, but may be isolated
  • varus force
  • associated with lateral collateral ligament damage
  • more: proximal fibula fracture
  • post-traumatic soft-tissue calcification adjacent to medial epicondyle of femur
  • ossification following injury to medial collateral ligament
  • do not misdiagnose as a fracture
  • more: Pellegrini-Stieda lesion
Approaches to radiographs

Article information

rID: 28760
Section: Approach
Synonyms or Alternate Spellings:
  • Knee X-ray
  • Knee xray

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Cases and figures

  • Figure 1: effusion ?
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  • Case 1: lipohemarthrosis
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  • Figure 2: tibiofemoral alignment
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  • Case 2: lateral tibial plateau fracture
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  • Figure 3: plateau review
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  • Case 3: Segond fracture
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  • Figure 4: patella
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  • Case 4: tibial eminence fracture
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  • Figure 5: radiographic anatomy - AP view
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  • Case 5: patella fracture
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  • Figure 6: radiographic anatomy - lateral view
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  • Case 6: distal femoral fracture
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  • Case 7: fibular head fracture
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  • Case 8: Pellegrini-Stieda lesion
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