Knee (lateral view)

Last revised by Andrew Murphy on 28 Oct 2021

The lateral knee view is an orthogonal view of the AP view of the knee. The projection requires the patient to 'roll' onto the side of their knee, hence it is not an appropriate projection in trauma, in all suspected traumatic injuries of the knee, the horizontal beam lateral method should be utilized. 

This is often performed on bed-bound patients with suspected arthritis, it is an orthogonal view of the AP projection and demonstrate the joint space, yet sacrifices any assessment of fluid levels. 

  • the patient is laying on side of interest with the knee of interest closest to the table and the other lower limb rolled anteriorly
  • affect knee is flexed slightly ≈ 30° (to the best of patient's ability)  anything more than 30° is less than ideal as the patella begins to move inferior and the soft tissues begin to compress 
  • medial-lateral projection
  • centering point
    • center to the knee joint 1.5-2.0 cm distal to the apex of the patella or at the tibial tuberosity if the patella is affected by certain injury patterns
  • collimation
    • superior to include the distal femur
    • inferior to include the proximal tibia/fibula
    • anterior to include the skin margin 
    • posterior to include skin margin
  • orientation  
    • landscape
  • detector size
    • 35 cm x 43 cm
  • exposure
    • 60-70 kVp
    • 7-10 mAs
  • SID
    • 100 cm
  • grid
    • no

A true lateral projection will have the following characteristic:

  • superimposition of the medial and lateral condyles of the distal femur 
  • an open patellofemoral joint space 
  • slight superimposition of the fibular head with the tibia 

The distal femoral condyles have distinct features that can be used for differentiation and hence positional errors that can be corrected.

The medial condyle has a medial adductor tubercle, located superior to the medial epicondyle,  a bony protuberance that acts as the attachment point the adductor minimus and the hamstrings part of the adductor magnus.
The lateral condyle has the condylopatellar sulcus also known as the lateral notch, a groove in the lateral femoral condyle. The easy way to remember is femoral is flat.

  • medial adductor tubercle is posterior to the lateral condyle
    •  rotate the knee externally to bring it anterior
  • medial adductor tubercle is anterior to the lateral condyle
    • rotate the knee internally to bring it posteriorly
  • medial condyle is proximal to the lateral condylar
    • perform adduction
  • medial condyle is distal to the lateral condyle
    • perform abduction

For an interactive case exploring these concepts see here

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Cases and figures

  • Figure 1: normal lateral knee
    Drag here to reorder.
  • Figure 2: medial adductor tubercle in profile
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  • Figure 3: projection requiring caudal angle
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