Sacrum & SI joints X-ray positioning

How to position for each of the 3 sacrum & SI joints X-ray views: where the patient goes, where to centre, which receptor and distance to use, and what a good image looks like.

By the ScanFlo Editorial Team · Updated 6 October 2026

X-ray positioning/Sacrum & SI joints

The routine sacrum & SI joints views are Sacrum AP and sacroiliac joints. Coccyx AP and Sacrum and coccyx lateral come in when you need to answer a particular question, or when the patient can't manage a routine view. Each guide walks you through the set-up step by step, with a short video, exposure settings for different patient sizes and what a good image should show.

A radiographer is still checking these guides.

Routine views

Sacrum AP and sacroiliac joints →Supine · 100 cm · centring point: 3 cm above the symphysis

Extra views

Coccyx AP →Supine · 100 cm · centring point: 5 cm above the symphysis

Sacrum and coccyx lateral →Lateral recumbent · 100 cm · centring point: the sacrum, 10 cm posterior to the anterior superior iliac spine

All views in this region

• Sacrum AP and sacroiliac joints
• Coccyx AP
• Sacrum and coccyx lateral

Quick reference

Where to centre, how far and which receptor, for every sacrum & si joints view at a glance. Open a guide for the full set-up.

Mistakes that lead to repeats

• Sacrum foreshortened on the sacrum AP and sacroiliac joints: angle 15° cephalad.
• Coccyx behind the symphysis on the coccyx AP: angle 10° caudad.
• Coccyx burnt out on the sacrum and coccyx lateral: collimate and reduce mAs for the coccyx.

Common questions

Which sacrum & SI joints views are routine?

Usually Sacrum AP and sacroiliac joints.

What distance (SID) do sacrum & SI joints X-rays use?

100 cm for every sacrum & SI joints view here.

Do sacrum & SI joints X-rays need a grid?

Yes, every view here is taken with a grid.

← All positioning regions