Sacroiliac joints (posterior oblique view)

The sacroiliac posterior oblique view is used to demonstrate the sacroiliac joints in an open profile. It is commonly used in conjunction with the sacroiliac AP view. Clinical indications include sacroiliitis and ankylosing spondylitis 1

  • patient is positioned in an oblique position, approximately 25-30 degrees RPO or LPO 2
  • the patients upside is the side of interest
  • for example if you are imaging the right SI joint, the patient is positioned LPO .
  • incorporate the use of a radiolucent cushion to maintain patient position 
  • most commonly performed supine 
  • posterior oblique view
  • centring point
    • directed 2.5cms medial to the upside ASIS
  • central ray
    • perpendicular to the IR
  • collimation
    • must adhere to the ALARA principle given the region exposed via the primary beam
    • close collimation to the area of interest, each SI joint is imaged individually
  • orientation  
    • portrait 
  • detector size
    • 24x30 cm 
  • exposure
    • 70 kVp
    • 20 mAs 
  • SID
    • 110 cm
  • grid
    • yes
  • adequate penetration should clearly demonstrate the sacroiliac joints
  • joint should appear open and in profile to the CR. 

Practical points

  • refer to department protocol regarding imaging of this region 

  • attempt to achieve similar positioning for both sides, in order for accurate comparative assessment 


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Article information

rID: 50480
Section: Radiography
Synonyms or Alternate Spellings:

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