Medial Branch Block

A medial branch block is an injection of local anaesthetic placed near small nerves called medial branch nerves in your spine. These nerves carry pain signals from the facet joints (the small joints at the back of the spine) to the brain. By temporarily switching these nerves off, a medial branch block can help your doctor work out whether your neck, mid-back, or low back pain is coming from the facet joints and, in some cases, provide short-term pain relief.

1. What Is a Medial Branch Block?

Facet joints are small joints on each side of the spine at every level. Like other joints in the body, they can develop arthritis, inflammation, or wear and tear. When irritated, they can cause deep, aching pain in the neck, mid-back, or low back, often called axial spine pain because it stays mainly around the spine rather than shooting down an arm or leg.

Medial branch nerves are tiny nerves that sit just outside the facet joints. Their job is to carry pain signals from the facet joints to the spinal cord and then to the brain. They do not control muscle strength or sensation in the arms or legs.

A medial branch block involves injecting a very small amount of local anaesthetic (similar to the numbing medicine used by dentists) near these medial branch nerves. The procedure can be performed at different parts of the spine:

Cervical spine – neck
Thoracic spine – mid-back
Lumbar spine – lower back

The main purpose of a medial branch block is diagnostic – to help confirm whether your facet joints are the main source of your pain. If numbing the medial branch nerves significantly reduces your pain for a few hours, this strongly suggests the facet joints are involved.

Medial branch blocks can also have a therapeutic role. Some people experience pain relief that lasts longer than the numbing medicine itself, even up to days or weeks. Newer research, including studies published up to 2024, supports this short-term benefit in selected patients, although it is usually not as long-lasting as other procedures like radiofrequency ablation.

2. Why Is It Done?

Medial branch blocks are used to help diagnose and sometimes manage pain thought to come from the facet joints. Typical symptoms include aching or stiffness in the neck, mid-back, or low back that:

Is mainly across the spine rather than shooting down a limb
May be worse with extension (leaning back), twisting, or prolonged standing
Is not clearly explained by a pinched nerve (radiculopathy) or disc herniation alone

Doctors may recommend a medial branch block for people with:

Facet arthropathy or facet joint arthritis seen on scans
Degenerative disc disease with associated facet joint strain
Whiplash-associated neck pain where facet joints are suspected
Spondylosis (age-related wear and tear of the spine)
Persistent axial spine pain without clear nerve root involvement

A common situation is a person who has had neck or low back pain for months to years, has tried physiotherapy, exercise, medication, and other conservative treatments, but still has significant pain affecting daily life. Imaging (such as MRI or CT) may show degenerative changes but not a single obvious cause. In this setting, a medial branch block can help identify whether the facet joints are a major pain generator.

Medial branch blocks are also used to select patients who are likely to benefit from radiofrequency ablation (RFA). RFA uses heat to create a longer-lasting interruption of pain signals in the medial branch nerves. Because RFA is more invasive and aims for longer-term relief, most guidelines recommend doing diagnostic medial branch blocks first to confirm that targeting these nerves makes sense.

3. What Happens During the Procedure?

Medial branch blocks are usually done as a day procedure in a pain clinic, radiology department, or operating room.

Before the procedure

Your doctor will review your medical history, medications, allergies (including to local anaesthetic or contrast dye), and recent imaging.
You may be asked to stop or adjust certain blood thinners in advance, following specialist advice.
You will usually be able to eat and drink normally, unless your clinic gives different instructions.

Sedation

Most medial branch blocks are done with you awake and lying comfortably. No sedation is usually required. Light sedation may be offered if you are very anxious or have difficulty lying still, but being as awake and aware as possible can help you judge your pain accurately after the injection.

Imaging guidance

The doctor uses imaging to guide the needle accurately to the area around the medial branch nerves. Two main imaging methods are used:

Fluoroscopy (X-ray) – the most common approach; shows the bones of the spine and guides the needle into the correct position. A small amount of contrast dye may be injected to confirm placement.
Ultrasound – used in some centres, especially in the neck or in patients where X-ray exposure is best minimized.

The injection itself

You will lie on an X-ray or procedure table, usually on your stomach for lumbar or thoracic blocks, or on your stomach or side for cervical blocks.
The skin over the target area is cleaned with antiseptic solution.
A small amount of local anaesthetic is injected into the skin to numb the area; this may sting briefly.
Using imaging guidance, the doctor advances a thin needle to where the medial branch nerves run along the bone.
A very small volume of local anaesthetic (often 0.3–0.5 mL per nerve) is injected near each medial branch nerve at the target levels. Sometimes, a tiny amount of steroid is added, but many guidelines recommend local anaesthetic alone for purely diagnostic blocks.
Usually 2–3 levels are treated in one session on the painful side, and sometimes on both sides (bilateral) if your pain is across the midline.

The whole procedure typically takes 15–30 minutes, though you may be in the clinic for longer to allow for preparation and observation afterwards.

Monitoring your pain afterwards

The hours immediately after the injection are critical for diagnosis. You will be asked to:

Perform some of the movements or activities that normally trigger your pain (within safe limits)
Rate your pain regularly using a numeric rating scale (for example, 0–10, where 0 is “no pain” and 10 is “worst imaginable pain”)
Record these ratings in a pain diary for at least 4–6 hours after the block, or as directed by your doctor

Your doctor will use this information to judge how successful the block was and to plan the next steps.

4. Interpreting the Results — The Diagnostic Value

The key question with a medial branch block is: Did numbing the medial branch nerves significantly reduce your usual pain during the time the local anaesthetic was working?

Most local anaesthetics used for medial branch blocks act for about 2–6 hours. During this “anaesthetic window,” your pain diary helps your doctor interpret the results.

Positive diagnostic block

If your pain improves by around 50–80% or more during the anaesthetic window, this is usually considered a positive block. Different guidelines and clinics may use slightly different thresholds (for example, at least 50% versus at least 80% relief), but the general idea is that your pain should be clearly and meaningfully better while the nerves are numb.

Why are two blocks often recommended?

A single medial branch block can sometimes give a false-positive result. This can happen for several reasons, such as spread of anaesthetic to nearby structures, expectation effects, or natural fluctuations in pain. To reduce this risk, many professional guidelines recommend doing two separate diagnostic blocks on different days, often using different local anaesthetics.

If both blocks give a similar, clearly positive response (for example, 50–80% or greater pain relief during the anaesthetic window), this provides strong evidence that the facet joints supplied by those medial branch nerves are the main source of pain. In that case, you may be considered a good candidate for radiofrequency ablation.

Negative or unclear block

If you experience little or no improvement in your typical pain (for example, less than 30–50% relief) during the anaesthetic window, it is less likely that the targeted facet joints are the primary cause of your pain. Your doctor may:

Re-check your pain diary and activities to make sure the test was accurate
Consider whether another pain source (disc, muscle, nerve root, or other structure) might be more important
Discuss other treatment options instead of RFA

Sometimes the result is equivocal – for example, mild but not clear relief, or difficulty judging pain because of sedation or other factors. In these situations, your doctor may suggest repeating the block, adjusting the technique, or exploring other diagnostic approaches.

5. Does It Also Relieve Pain? (Therapeutic Role)

Medial branch blocks were originally designed and used as diagnostic tests, not long-term treatments. The expectation was that pain relief would last only as long as the local anaesthetic remained active.

However, research over the past decade, including studies published through 2024, has shown that some patients experience:

Pain relief that lasts beyond the immediate anaesthetic window
Improved movement and function for days or sometimes weeks
Reduced need for pain medication in the short term

The exact reasons for this longer-lasting benefit are not fully understood. Possible explanations include calming of irritated nerves, reduction in muscle spasm around the joints, or a reset in pain signalling pathways. In some protocols, a small amount of steroid is added, which may also extend relief in certain cases.

Despite this, medial branch blocks are generally not considered a long-term solution. Compared with radiofrequency ablation, which can sometimes provide months of relief when successful, the pain improvement from medial branch blocks is usually shorter-lived.

In practice, medial branch blocks can be useful as:

A bridge while you are waiting for radiofrequency ablation or other treatments
An option for people who are not candidates for RFA because of medical, anatomical, or personal reasons
A way to manage flare-ups in carefully selected situations

Your doctor should explain whether your block is being used mainly for diagnosis, for short-term treatment, or both, and how this fits into your overall pain management plan.

6. What to Expect After the Procedure

After the injections, you will usually be monitored for a short time in the clinic to make sure you feel well and can walk safely. Most people can go home within an hour.

Monitoring your pain (4–6 hour window)

The most important task after a medial branch block is to record your pain levels for at least 4–6 hours. To make this as accurate as possible:

Use the same pain rating scale your clinic gave you (often 0–10).
Write down the time and your pain score at regular intervals (for example, every 30–60 minutes).
Try to do the activities that usually bring on your pain (within safe limits) – such as walking, bending, or standing – so you are testing your typical pain, not just resting pain.
Note any side effects such as numbness, weakness, dizziness, or unusual symptoms and report these if they are concerning.

Your clinic may provide a specific pain diary form or an app to help with this.

Activity and self-care

You can usually return to normal light activities the same day, as long as you feel well.
A small amount of soreness or bruising at the injection site is common and usually settles within a day or two.
An ice pack wrapped in a cloth can be used on the injection area for 10–15 minutes at a time if needed.
If you received sedation, you should avoid driving, operating machinery, making important decisions, or signing legal documents for the rest of the day. Arrange for someone to take you home.

Communicating results

Your pain diary and your personal description of how you felt after the block are shared with the doctor who performed the procedure and your referring clinician. Together, they will interpret the results and discuss the next steps with you, which may include repeat diagnostic blocks, radiofrequency ablation, or alternative treatments.

7. Risks and Considerations

When performed by experienced clinicians using imaging guidance, medial branch blocks are generally considered safe. However, as with any medical procedure, there are potential risks and side effects.

Common effects (usually mild and short-lived)

Soreness or bruising at the injection site
Temporary increase in pain from the injection needle or positioning
Transient numbness or heaviness around the injection area

Uncommon risks

Bleeding or haematoma (a collection of blood under the skin), especially in people on blood thinners or with bleeding disorders
Infection at the injection site or, rarely, deeper infection
Allergic reaction to local anaesthetic or contrast dye
Worsening of pain for a short period before improvement

Rare but more serious risks

Nerve injury, which could cause weakness, numbness, or persistent pain
Inadvertent injection into a blood vessel (intravascular injection), which is why careful aspiration and small test doses are used
Allergic or adverse systemic reaction requiring urgent treatment

If you have multiple medial branch blocks or repeat procedures at the same levels, there is a small cumulative risk of these complications, although the overall risk remains low in most people.

Contrast dye

Some centres use a small amount of contrast dye under fluoroscopy to confirm the needle is in the correct place and not in a blood vessel. If you have a known contrast allergy, kidney problems, or a history of severe reactions to injections, you should tell your doctor in advance so they can plan safely.

Your individual risk profile depends on your other medical conditions, medications, and anatomy. Your clinician should discuss the likely benefits and potential risks with you before you consent to the procedure.

8. Key Points

A medial branch block is an injection of local anaesthetic near small nerves that carry pain from the facet joints in your spine.
Its main purpose is to diagnose whether your facet joints are the major source of your neck, mid-back, or low back pain.
The procedure is usually done under X-ray or ultrasound guidance, takes about 15–30 minutes, and often treats 2–3 levels in one session, sometimes on both sides.
Careful recording of your pain for 4–6 hours after the injection is essential to interpret the results accurately.
If your pain improves by around 50–80% or more during the anaesthetic window, the block is considered positive and you may be a candidate for radiofrequency ablation.
Newer research shows that medial branch blocks can sometimes provide short-term therapeutic relief beyond the numbing period, but they are not typically a long-term solution.
The procedure is generally safe when done by trained clinicians, with most side effects being mild and temporary.
Your overall pain management plan should combine procedures like medial branch blocks with exercise, rehabilitation, and self-care strategies tailored to you.

9. Questions to Ask Your Doctor

How many spinal levels will be injected, and on which side or sides?
Will I need a second confirmatory medial branch block before radiofrequency ablation is considered?
What percentage of pain relief should I aim to record for this test to be considered positive?
How do you want me to keep a pain diary on the day of the procedure, and what activities should I try to do?
What are the next steps if my block is positive? What if it is negative or unclear?
Do you plan to use only local anaesthetic, or will any steroid or contrast dye be included?
What are the specific risks for me, given my other medical conditions and medications?

Disclaimer: The information in this article is intended for general educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always speak with a qualified healthcare professional before making decisions about your care.