A facet block is an injection of numbing medication and, often, a steroid into or near one of the small joints that connect each vertebra in your spine. These joints, called facet joints, help support your spine and allow it to bend and twist. When they become inflamed or arthritic, they can cause significant back or neck pain. A facet block serves two purposes: it can diagnose whether a specific facet joint is actually the source of your pain, and it can treat that pain directly.
Why Facet Joints Cause Pain
Your spine has pairs of facet joints at every level, from your neck down to your lower back. Together with the discs between your vertebrae, these joints bear weight and guide movement. Over time, they can develop arthritis, become inflamed from injury, or simply wear down. Facet joint pain has been a leading contributor to global back disability since at least 1990, and it tends to produce an aching pain that worsens when you lean backward, twist, or stand for long periods. The pain sometimes radiates into the buttocks or thighs (for lower back joints) or into the shoulders and upper back (for neck joints), which can make it tricky to distinguish from other spinal conditions.
Diagnostic vs. Therapeutic Blocks
Facet blocks play two distinct roles, and understanding the difference matters because it affects what happens next in your treatment.
A diagnostic block uses only a numbing agent. The goal is to temporarily shut off pain signals from a specific joint so your doctor can confirm that joint is the source of the problem. For a diagnostic block to count as “positive,” it needs to relieve at least 80% of your primary pain for as long as the numbing agent is expected to last. Most insurance guidelines, including Medicare criteria, require two separate positive diagnostic blocks before approving more advanced treatments. The second block is typically performed at least two weeks after the first.
A therapeutic block includes both a numbing agent and a steroid. The numbing agent gives you immediate but short-lived relief, while the steroid reduces inflammation over the following days. The steroid takes two to three days to start working and typically peaks around two weeks. One study of patients with mild to severe facet joint arthritis showed significant improvement in pain scores at three months after steroid injection.
Facet Block vs. Medial Branch Block
You may hear these terms used interchangeably, but they’re slightly different procedures. A facet joint injection delivers medication directly into the joint capsule itself. A medial branch block targets the tiny nerve just outside the joint that carries pain signals from it. In practice, medial branch blocks are often preferred for diagnostic purposes because of their specificity in pinpointing facet-related pain. Facet joint injections tend to be used when both diagnosis and treatment are goals, since the steroid inside the joint can directly reduce inflammation.
What the Procedure Feels Like
Facet blocks are outpatient procedures, typically done in a clinic or ambulatory surgery center. You lie face down on a table, and the skin over the injection site is numbed with a small amount of local anesthetic. Your doctor uses real-time X-ray imaging (fluoroscopy) to guide a thin needle precisely into or next to the facet joint. You may feel pressure or a brief sting when the needle reaches the joint, but the procedure itself usually takes only a few minutes per joint. Multiple joints can be treated in one session.
The entire visit, including preparation and a short observation period afterward, generally takes under an hour. You’ll need someone to drive you home.
How to Prepare
If you take blood-thinning medications, your doctor will give you specific instructions about when to stop them before the procedure. You should mention all medications and supplements you’re currently taking, since some over-the-counter painkillers and supplements also affect bleeding. Most clinics ask you to arrange a ride home, since the local anesthetic can temporarily affect your coordination or comfort level while driving.
Recovery and Activity Restrictions
Recovery is quick. You can expect some soreness at the injection site for a day or two. Showering is fine the day after, and light activity around the house is encouraged from the start. The main restriction is avoiding heavy exercise, intense cardio, or weight training for at least 48 hours.
A common pattern after the injection: your pain improves right away from the numbing agent, returns later that day as it wears off, then gradually improves again over the next few days as the steroid takes effect. If this happens, it’s a good sign the block is working therapeutically.
How Long Relief Lasts
Pain relief from facet blocks is variable. Some people get weeks of relief, others get months. Studies show significant pain improvement lasting up to three months with steroid injections, but the relief is transient by nature. Repeated injections may be needed. Your doctor should set expectations that results differ from person to person, and a single injection rarely provides permanent relief.
Safety and Side Effects
Facet blocks have a strong safety profile. A large study tracking over 7,500 procedures involving 43,000 individual nerve blocks found zero major complications. No cases of nerve damage, spinal cord injury, infection, or significant bleeding occurred. Minor events were common but mostly trivial: small amounts of local bleeding at the needle site happened in about 70% of cases (think a few drops, similar to a blood draw), and minor oozing occurred in about 20%. A small bruise formed in fewer than 1% of procedures. Nerve root irritation, which can cause a temporary flare of pain or tingling, occurred in only 0.1% of cases.
Intravascular penetration, where the needle briefly enters a small blood vessel, happened in about 11% of cases overall but was highest in the cervical (neck) region at 20% and lowest in the lumbar (lower back) region at 4%. This is one reason fluoroscopic guidance is standard: it lets the doctor see the needle position and adjust in real time.
What Happens If the Block Works
If a diagnostic facet block relieves at least 80% of your pain, it confirms the facet joint as your pain source. After two confirmed positive blocks, your doctor may recommend radiofrequency ablation, a procedure that uses heat to interrupt the nerve carrying pain signals from the joint. This can provide longer-lasting relief, often six months to a year or more, because the nerve takes time to regenerate. The two-block requirement exists to reduce false positives and make sure the right joint is being targeted before committing to a more involved procedure.
If the block doesn’t relieve your pain, that’s valuable information too. It suggests the facet joint isn’t the primary pain generator, and your doctor will look at other possible causes like disc problems, muscle issues, or nerve compression.