Radiofrequency Denervation for Facet Joint Pain: A Step-by-Step Explanation

Why low back pain is complex

Low back pain is one of the most common reasons people seek medical help, yet it is also one of the most complex conditions to diagnose and treat; in many patients, pain does not arise from a single structure but from a combination of joints, discs, muscles, and nerves. One important — and often misunderstood — source of low back pain is the lumbar facet joints; radiofrequency treatment can be an effective option for selected patients, but only when used as part of a structured, stepwise diagnostic pathway.

Lumbar spine anatomy (simple explanation)

The lumbar spine consists of five vertebrae stacked one on top of another; between the vertebrae sit the intervertebral discs, which act as shock absorbers, and at the back of each vertebra are two small joints called facet joints.

Facet joints guide movement and provide stability, particularly during bending and twisting; they are lined with cartilage and surrounded by a joint capsule, and they can become painful with wear-and-tear, overload, altered biomechanics, or after injury.

Lumbar Facet Joints

What is lumbar facet joint pain?

Facet joint pain is typically felt in the lower back and is often worse with extension (arching backwards) or rotation; symptoms may fluctuate with posture and activity and can coexist with other sources of pain.

Importantly, facet joint changes on MRI or X-ray do not automatically mean the facet joints are the source of pain; many people have degenerative findings on scans without symptoms, so diagnosis relies on clinical assessment combined with targeted diagnostic injections.

Nerve supply to facet joints (why we treat medial branches)

Pain arising from the lumbar facet joints is transmitted by small sensory nerves known as the medial branches of the dorsal rami. After each spinal nerve exits the spine, it divides into a ventral ramus (which supplies the limbs and front of the body) and a dorsal ramus, which supplies the muscles and joints at the back of the spine. The dorsal ramus then further divides into medial and lateral branches.

The medial branch is the key nerve of interest in facet joint pain. It provides sensory supply to the facet joints and also innervates some of the small stabilising muscles of the spine.

Importantly, each lumbar facet joint receives nerve supply from two medial branches:

• one arising from the dorsal ramus at the same spinal level, and

• one from the level above.

For example, the L4–L5 facet joint is supplied by:

• the medial branch of the L3 dorsal ramus, and

• the medial branch of the L4 dorsal ramus.

This dual innervation is the reason why radiofrequency treatment typically involves targeting multiple medial branches, rather than a single nerve. Treating only one branch would be insufficient and is unlikely to provide meaningful pain relief.

Another important point is that the medial branches lie outside the facet joint itself, running along predictable bony landmarks on the spine. This makes them ideal targets for precise, image-guided procedures, such as medial branch blocks and radiofrequency denervation, without entering the joint.

By selectively interrupting pain signals carried by these medial branches, radiofrequency treatment aims to reduce facet-mediated pain while preserving overall spinal stability and movement.

A two-step pathway (why it matters)

Radiofrequency is not the first step; the standard pathway is to confirm facet joint contribution using diagnostic medial branch blocks before proceeding to radiofrequency where appropriate.

Medial branch blocks: what they are and how they work

Medial branch blocks are diagnostic injections performed using local anaesthetic only; they are designed to answer a single question: are the facet joints contributing to this person’s low back pain?

Because medial branches supply the facet joints, placing local anaesthetic around these medial branches temporarily “switches off” the facet joint’s nerve supply while the anaesthetic is active; during this window, the facet joint cannot send pain signals in the usual way.

If pain improves clearly while the local anaesthetic is working, this supports the facet joints as a meaningful contributor to symptoms; if there is no change, it makes facet joint pain less likely as a major driver.

How long do medial branch blocks last? Any pain relief is expected to be short-lived and typically lasts a few hours, often up to around 6–8 hours, depending on the local anaesthetic used; this is why the injection is diagnostic rather than a long-term treatment.

Why we ask patients to “test” the injection: To interpret the result accurately, patients are encouraged to gently provoke their usual pain during the anaesthetic window by doing safe, familiar movements that normally trigger symptoms (for example walking, standing, bending, or twisting within limits advised by the clinician).

If pain is significantly reduced during activities that would normally provoke symptoms, this is a stronger diagnostic result; resting completely after the injection can make the outcome difficult to interpret.

Mini infographic: Facet joint → medial branch → temporary block

What is a “positive” response to blocks?

A positive response usually means a clear reduction in the patient’s usual pain during the anaesthetic window, ideally alongside improved movement or function, with pain returning once the anaesthetic wears off.

Relief does not need to be complete to be meaningful, particularly because low back pain commonly has more than one contributing source.

Interpreting partial responses (why 100% relief is uncommon)

Low back pain is frequently multifactorial, meaning pain can arise from a combination of facet joints, discs, muscles, sacroiliac joints, or nerve-related sources; for this reason, complete pain relief from diagnostic injections is uncommon.

A partial response often indicates that facet joints are one contributor rather than the only driver of pain, and radiofrequency can still be considered in selected cases with the understanding that it may reduce part, but not necessarily all, of the pain.

Why radiofrequency may not work despite a positive block

Although a positive medial branch block suggests facet joint contribution, it does not guarantee that radiofrequency will provide the desired level of relief; several factors can explain this.

• Multiple pain generators: other structures may continue to produce pain even if the facet-mediated component improves.
• Temporary anaesthetic effects: local anaesthetic can sometimes spread to nearby structures and produce broader short-term improvement than the facet contribution alone.
• Partial facet mediation: if facet joints are one contributor among several, radiofrequency may help but will not remove all symptoms.
• Anatomical variation and technical factors: medial branch anatomy varies, and accurate targeting is essential for best outcomes.

A positive block is therefore best understood as a guide rather than a guarantee, and careful interpretation is essential.

What does lumbar radiofrequency involve?

Radiofrequency treatment involves placing specialised needles near the medial branches under imaging guidance and applying controlled heat to reduce pain signalling from the facet joints; the aim is to reduce the facet-mediated component of pain without damaging the spine.

When does it work? Radiofrequency does not work immediately and commonly takes around 6–8 weeks to reach its full effect.

Can pain flare up? Patients may experience a temporary flare of pain for 1–3 weeks before symptoms settle; an early flare does not necessarily mean the treatment has failed.

Needle position for medial branch blocks and radiofrequency treatment

How long can radiofrequency last?

Duration of benefit varies between individuals, but relief commonly lasts months and sometimes longer; the treated nerves can regenerate over time.

If radiofrequency has been helpful, repeat treatment may be considered if symptoms recur, alongside ongoing rehabilitation.

Rehabilitation (the key to durable improvement)

Radiofrequency is best viewed as a window of opportunity to improve movement tolerance and support rehabilitation; physiotherapy, movement re-education, and strength work often help consolidate benefits.

Without rehabilitation, benefits may be shorter-lived because the underlying biomechanical and conditioning contributors to pain may remain.

Complex spines and scoliosis: why experience matters

Lumbar medial branch radiofrequency is technically demanding, particularly in patients with advanced degenerative change, severe facet hypertrophy, altered anatomy after surgery, or significant scoliosis and spinal rotation, where normal landmarks may be distorted.

In these situations, a thorough understanding of fluoroscopic anatomy and extensive procedural experience are important to identify targets accurately and optimise outcomes, because small technical inaccuracies can significantly influence effectiveness.

Expertise at Pain Spa

Dr Krishna has extensive experience in managing complex spinal pain, including patients with significant degenerative change and severe scoliosis; a consultant-led approach, careful interpretation of diagnostic blocks, and advanced fluoroscopic technique help tailor treatment to the individual rather than applying a one-size-fits-all pathway.

This approach is particularly important when spinal anatomy is altered or when pain is multifactorial, as careful planning and technique can help maximise the chance of meaningful improvement.

Key takeaways

• Facet joints are a common contributor to low back pain, but pain is often multifactorial.
• Medial branch blocks are diagnostic and typically last a few hours, often up to around 6–8 hours.
• Patients are encouraged to gently test their usual pain triggers during the anaesthetic window to interpret results accurately.
• A partial block response often means only part of the pain is facet-mediated; radiofrequency may still help with realistic expectations.
• Radiofrequency often takes around 6–8 weeks to reach full effect and may involve a short-term flare.
• Experience and fluoroscopic anatomical expertise are especially important in complex spines and scoliosis.

Frequently asked questions

Is radiofrequency the same as “burning the nerves”? Radiofrequency uses controlled heat to interrupt pain signals carried by the medial branches supplying the facet joints. The aim is to reduce facet-mediated pain while preserving spinal structure.

Will radiofrequency make my spine unstable? No. The medial branches are small sensory nerves and do not control the major muscles of the spine. Strengthening and rehabilitation remain important for long-term spinal health.

Can I have radiofrequency if my medial branch block only helped a little? Yes, in selected cases. A partial response often means facet joints are one contributor rather than the only source of pain. Radiofrequency may still help reduce part of the pain, with realistic expectations.

When should I decide whether it has worked? Benefit is usually assessed at around 6–8 weeks, as improvement can be gradual and some people experience a temporary flare-up first.

Can radiofrequency be repeated? If it provided meaningful relief and symptoms later return due to nerve regeneration, repeat radiofrequency can be considered as part of an overall management plan.

Please contact Pain Spa at clinic@painspa.co.uk or via our website www.painspa.co.uk. to arrange a consultation or if you have any further questions.