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Sacral Lateral Branch Block and Sacro-iliac Joint Injection


A lateral sacral branch block is where local anaesthetic is injected onto the nerves of the sacro-iliac joints (at the base of the spine). It is used as a diagnostic tool to determine whether back pain is being caused by these joints.

It works by temporarily disabling pain signals from the sacro-iliac joints – if the procedure results in a significant decrease in back pain, it indicates that these joints are the source of the pain.

In the case of sacro-iliac joint steroid injection, the pain relief from this procedure may last several weeks.


Lower back pain arising from the sacroiliac joints.

Preoperative Instructions

For a lateral sacral branch block or sacro-iliac joint steroid injection (as a primarily diagnostic procedure), it is important to be able to reproduce the pain at the time of the procedure. For this reason, you should stop taking any pain medication around 5-6 hours beforehand. If there is no pain on the day you are due to undergo a lateral sacral branch block, we may suggest postponing it to a later date.

You should avoid undergoing any other medical procedures, such as for example dental treatment or a colonoscopy, within 48 hours (before or after) of a cervical medial branch block.

Please also let us know ahead of the procedure if…

  • You are taking any antibiotics.
  • You have a pacemaker or defibrillator.
  • You are ill (in which case we may need to postpone the procedure).

You should also not drive yourself to or from the appointment, or drive within a 24-hour period after the procedure.


You are asked to lie face down on a theatre table. An IV line is put in place in your arm or hand to administer light sedation.

The injection site is then cleaned and numbed with a local anaesthetic and a thin needle is inserted at the injection site and then guided, by means of a mobile x-ray unit, to the correct position.

Once the procedure is complete, you will need to spend around 1 hour under observation before being able to go home. While under observation you will be asked to see if you can reproduce the pain you normally feel and let the doctor know if there has been any reduction in pain, and how much. It is usual to maintain a 'pain diary' for around a week after the procedure to track any changes in level and intensity of pain.

Postoperative Instructions

After the procedure you are able to return home (although as explained in the preoperative instructions above, you should not drive yourself. There is no restriction on day-to-day activities. In some (relatively rare) cases there may be some discomfort and/or bruising to the skin at the injection site. Any feeling of numbness in the legs or buttocks generally goes away within a few hours.


A lateral sacral branch block procedure or sacro-iliac joint injection is a relatively low risk procedure – however all medical treatment comes with some level of risk. Possible complications may include…

  • Bleeding.
  • Infection.
  • Pain at injection site.