Knee (oblique view)

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The knee oblique view is an additional projection requested to examine the knee joint in greater detail, often in the absence of a CT scanner. The view is comprised of both an internal and external oblique.

Indications

The internal and external oblique views of the knee can showcase pathology such as fractures and degenerative bone changes especially on the anterolateral or posteromedial aspects of the knee .

Patient position

  • patient is supine on the table with the knee and ankle joint in contact with the table
  • leg is extended
  • knee is rotated internally or externally 45 degrees depending on the projection 

Technical factors

  • anteroposterior projection
  • centering point
    • center of the knee 1.5 cm distal to the apex of the patella
  • collimation
    • superior to include the distal femur
    • inferior to include the proximal tibia/fibula
    • lateral to include the skin margin 
    • medial to include medial skin margin
  • orientation  
    • portrait
  • detector size
    • 24 cm x 30 cm
  • exposure
    • 60-70 kVp
    • 7-10 mAs
  • SID
    • 100 cm
  • grid
    • no

Image technical evaluation

  • internal rotation
    • lateral condyles of both the tibia and femur are well displayed 
    • the fibula head should be free from almost all superimposition
  • external rotation 
    • medial condyles of both the tibia and femur are well displayed 
    • the fibula head will be superimposed by the tibia 

Practical points

Not often performed, this view is valuable in the absence of CT. It is worth explaining to the patient that rotation occurs at the hip and not the knee, to ease anxiety.