SI Joints
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RPO/LPO Obliques (25–30°)

IMAGE RECEPTOR
Patient position
Supine.
Part position
MSP centered for AP; affected side elevated 25–30° for obliques (LPO = right SI joint).
Central ray
AP: 30° cephalic to 1.5 in superior to symphysis. Oblique: perpendicular to 1 in medial to elevated ASIS.
IR placement
24x30 cm.

Tech pearls

  • Mnemonic: 'side UP' shows that SI joint on oblique.
  • Ankylosing spondylitis classically begins at SI joints.
AP Axial (30° cephalic)Series overview