Genicular Nerve Block

Medically reviewed by Joshua L. Hare, DO, Founder & Medical Director

Conditions Treated

Chronic knee osteoarthritis pain, post-total knee replacement pain, chronic knee pain not responsive to other treatments

Genicular Nerve Block at a Glance

Purpose	Diagnostic — it answers whether the genicular nerves carry your knee pain
Type of procedure	Outpatient, image-guided (fluoroscopy)
Time in the procedure room	About 15–20 minutes
Anesthesia	Local anesthetic at the skin; the block itself is the anesthetic
Back to normal activity	Immediately — walking on the knee is part of the test
Relief lasts	Hours. That short window is the test; you track your pain while the anesthetic works
What a positive result means	50% or greater relief makes genicular nerve radiofrequency ablation the next option

What a Diagnostic Block Is

The knee joint reports its pain through small sensory branches — the genicular nerves.[1] A diagnostic block numbs those branches for a few hours and then asks a simple question: with the wiring quiet, did the pain drop? If it did, the nerves the block silenced are the ones carrying your pain, and treating them has a target. Relief that wears off as the anesthetic fades is the test doing its job. The block is a diagnostic test, not a treatment.

How It Works

Using fluoroscopic guidance, local anesthetic is injected around three genicular nerves:[1] the superior medial, superior lateral, and inferior medial genicular nerves at defined anatomical landmarks around the knee.

The landmarks matter because each genicular nerve runs close to bone at a predictable spot near the ends of the femur and shin bone. The fluoroscope puts the needle tip at those spots, a small volume of anesthetic goes in at each one, and the whole appointment takes about 15–20 minutes. There is no steroid to wait on and no lesion being made; the only medication is the local anesthetic.

Who It Helps — and Who It Does Not

The block is built for knees that stay painful after first-line osteoarthritis care has had a fair run. The 2019 American College of Rheumatology guideline makes strong recommendations for exercise, weight loss where it applies, topical and oral anti-inflammatories, and steroid injections into the joint[2] — that ladder comes first, and a lot of knees get better on it. The block is also used for knees that still hurt after a total knee replacement, where the hardware looks fine on imaging and the pain persists anyway.

What the block cannot do is treat anything. Patients hoping to skip straight to lasting relief sometimes ask why this step exists at all; the answer is that ablating nerves that were never carrying your pain trades a procedure for nothing. A negative block is a cheap answer to get before an ablation, not after.

The Day of the Block

1. Check-in and positioning. You lie on your back with the knee supported; the skin is cleaned, and your vital signs are monitored.
2. Numbing the skin. A small local anesthetic wheal is raised at each planned entry point.
3. Guided placement. Under fluoroscopy, the needle tip is walked to each genicular landmark in turn and confirmed on the image.
4. The injections. A small volume of local anesthetic is placed at each nerve. No lesion is made and nothing is implanted.
5. The test begins at discharge. You leave with a pain diary and instructions to use the knee normally — walk, climb the stairs you usually avoid — and score your pain over the next 4–8 hours.

Reading the Result

Your provider reads the diary against one threshold: we call relief of 50% or greater while the anesthetic worked a positive test, the same cut-off the randomized cooled radiofrequency trial used to select its patients,[3] and a positive test makes genicular nerve radiofrequency ablation worth discussing. Relief that faded by evening still counts as positive — the anesthetic is supposed to wear off. And a block that changed nothing rules these nerves out: ablation comes off the table, and the work-up moves on to the joint itself, the soft tissue, or the spine.

What the Evidence Shows

The randomized trial behind this pathway used the block exactly this way. Its subjects qualified only with severe knee osteoarthritis pain lasting more than 3 months, a positive response to a diagnostic genicular nerve block, and no response to conservative treatments[1] — and in that block-selected group, the ablation that followed reduced knee pain at 4 and 12 weeks against a sham procedure. The block is the trial's own screening step, which is why IPC will not skip it. In the ACR guideline the whole pathway sits downstream of the strongly recommended basics: a conditional recommendation for radiofrequency ablation for knee osteoarthritis.[2]

After the Block

The first hours	Use the knee normally and score your pain in the diary — this window is the entire test.
The rest of the day	The anesthetic fades and prior pain typically returns. Soreness at the injection sites settles on its own.
The follow-up	Your provider reads the diary with you and calls the block positive or negative. That result, not a scan, decides whether ablation is offered.

Common Questions

Why does the relief only last a few hours?

The block is local anesthetic and nothing else, so it is built to wear off within hours. That is deliberate: if the pain drops while the medicine works and returns as it fades, the nerves the block numbed are the source.

What should I do during the test window?

The things that usually hurt. A block scored from the recliner tells your provider very little — walk, take stairs, get up from low chairs, and write the scores down as you go rather than from memory that evening.

What happens if the block is positive?

You and your provider talk through genicular nerve radiofrequency ablation — the same three nerve targets, treated with controlled heat, with relief on the scale of months where the block gave hours.

What are the risks of the block itself?

Small ones: soreness or bruising at the injection sites that settles quickly, and the rare risks any injection carries. Your provider goes over the short list with you — against your health picture and your medications — before the appointment.

References

Clinical sources for this page.

1. Choi WJ, Hwang SJ, Song JG, et al. Radiofrequency treatment relieves chronic knee osteoarthritis pain: a double-blind randomized controlled trial. Pain. 2011;152(3):481–487. Back to first citation ↑
2. Kolasinski SL, Neogi T, Hochberg MC, et al. 2019 American College of Rheumatology/Arthritis Foundation Guideline for the Management of Osteoarthritis of the Hand, Hip, and Knee. Arthritis & Rheumatology. 2020;72(2). Back to first citation ↑
3. Davis T, Loudermilk E, DePalma M, et al. Prospective, multicenter, randomized, crossover clinical trial comparing the safety and effectiveness of cooled radiofrequency ablation with corticosteroid injection in the management of knee pain from osteoarthritis. Regional Anesthesia and Pain Medicine. 2018;43(1):84–91. PMC Back to first citation ↑