Knee (skyline Laurine view)

Mr Andrew Murphy et al.

The knee skyline Laurine view is an inferior-superior projection of the patella it is one of many different methods to obtain an axial projection of the patella. This projection is best suited to patients able to maintain a semi-recumbent position on the examination table.

  • patient is semi-recumbent on the table holding a detector superior of the patella in the landscape orientation 
  • patient's feet should be very close to the tube side of the bed (see technical factors)
  • the knee is bent close to 30°
  • often a pillow or cushion should be placed behind the patient to assist them in maintaining this position 
  • inferior-superior axial projection
  • centring point
    • the central ray will be angled 160° from the vertical axis( or 30° from horizontal), shooting inferior-superior towards the patella. This will require the tube to lay below the level of the examination table ; hence the patient should be as close to this end of the table as possible. 
    • apex of the patella
  • collimation
    • laterally to include the skin margins of the knee 
    • inferior to include the femoropatellar joint space 
    • superior to include medial skin margin
  • orientation  
    • landscape
  • detector size
    • 18 cm x 24 cm
  • exposure
    • 60-70 kVp
    • 7-10 mAs
  • SID
    • 100-120 cm
  • grid
    • no
  • patella should be free from superimposition of all bony structures
  • clear visualisation of the patellofemoral joint space 

This projection is one of the more technically demanding projections of, the lower limb. Hence it being one of seven techniques (that the author can find) to achieve it. 

This particular method has a high yield if your patients can tolerate the position. Some points to consider when performing this projection: 

  • dose
    • this projection often requires more dose than conventional knee radiographs due to tube angulation and, more often than not, a larger FFD 
  • tube angle 
    • 30°  from horizontal is the academically acceptable angle for this technique, however, by assessing the lateral projection and working out the optimal angle from the inferior-superior approach can be beneficial
  • patients feet
    • the patient's feet will be at the end of the table and often if not careful; the skyline projection may also be a heavily magnified projection of the distal phalanges; ensure the patient's feet are out of the primary beam
  • detector 
    • it is possible to use a detector stand rather than asking the patient to hold the detector, this alleviates the risk of motion artefact
  • the pen test 
    • turning the collimator light on, hold the other end of a pen and place it on the lateral border of the patella, if the patient is positioned correctly, the pen will cast a shadow on the detector

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Article Information

rID: 50634
Section: Radiography
Tags: cases, refs
Synonyms or Alternate Spellings:

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Cases and Figures

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    Figure 1: skyline projection demonstrating suboptimal collimation
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    Figure 2: vertical fracture of patella
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