What is a Diagnostic Facet Joint Nerve Block?

A diagnostic lumbar facet joint nerve block is an injection used to help determine whether your chronic lower back pain is originating from the facet joints in the spine. It involves injecting local anaesthetic near the medial branch nerves that carry pain signals from the
facet joints. If your pain significantly improves after the injection, this confirms that the facet
joints are a likely source of your symptoms.

What conditions do we offer this for?

We may offer this procedure for patients with:

  • Well localised, one-sided Chronic lower back pain suspected to arise from the lumbar facet joints
  • Postural or mechanical back pain (worse on standing, arching, or twisting)
  • Pain that has not responded to medication or physiotherapy
  • To assess suitability for radiofrequency denervation of lumbar medial branch nerves

Why is it done?

This procedure is carried out to:

  • Help identify whether the facet joints are the main source of your pain
  • Support diagnosis when imaging results (e.g. MRI) are inconclusive
  • Guide whether you may benefit from radiofrequency denervation
  • Provide temporary pain relief as a by-product of the diagnostic process

What does the procedure involve?

  • You will lie on your front on an X-ray table.
  • The skin is cleaned and numbed with local anaesthetic.
  • Under X-ray (fluoroscopy) guidance, fine needles are placed near the medial branch nerves.
  • A small amount of local anaesthetic only (no steroid) is injected.
  • You will be asked to monitor your pain levels closely in the hours following the injection.
  • The procedure takes 15–30 minutes and is done as a day case.

Benefits

  • Helps confirm the cause of your neck pain
  • May identify whether radiofrequency denervation is a suitable next step
  • Quick, minimally invasive procedure
  • Temporary pain relief can assist in physiotherapy or assessment

Side Effects

Very Common side effects

(may affect more than 1in 10 patients):
  • Pain or bruising at the injection site
  • Temporary increase in back pain
  • Mild numbness or discomfort around the back

Common side effects

(may affect up to 1in 10 patients):
  • Localised swelling or stiffness
  • Mild light-headedness or dizziness

Uncommon side effects

(may affect up to 1 in 1,00 patients):
  • Infection at the injection site
  • Temporary leg weakness or altered sensation

 Rare side effects

(may affect up to 1 in 1,000 patients):
  • Nerve injury or persistent numbness
  • Bleeding or haematoma
  • Allergic reaction to local anaesthetic

Aftercare Advice

  • You can usually go home the same day.
  • Avoid driving for 24 hours.
  • Note your pain levels carefully over the next 1-3 hours. Your doctor may ask you to perform normal movements to assess pain relief.
  • Resume normal activities gradually.
  • You may be asked to return for a repeat block to confirm findings or for radiofrequency treatment if pain relief was significant.

When to Seek Medical Attention

Please attend A&E immediately if you experience:
• Fever, chills, or signs of infection at the injection site
• New or worsening arm numbness or weakness
• Loss of bladder or bowel control
• Severe or ongoing neck pain not relieved by usual medication