Fluoroscopic Guided Knee Genicular Nerve Block – Technique and Overview

Name of Procedure

• Diagnostic Genicular Nerve Block (GNB)
• Therapeutic Genicular Nerve Block (GNB)

Sample Opnote

Goal

To block and/or administer medications to the genicular nerves that innervate the knee.

Indications

A diagnostic genicular nerve block might be performed to temporarily ameliorate pain from the knee from a variety of causes. It has the benefit of treating many causes such as arthritis, intraarticular pathology and even pain in patients who have had prior surgery or total and partial knee replacements.

This makes the procedure an option when intra articular treatments, such as a knee steroid or hyaluronic acid injection, aren’t an option.

The temporary block provides diagnostic value because a temporary relief in pain can help to determine if the knee is the source of the pain. A single block, or two blocks as part of a double comparative set of diagnostic blocks, might help inform if a radiofrequency ablation of the genicular nerves should be performed for the patient.

A therapeutic genicular nerve block (such as injection with a steroid) might be performed to ameliorate pathology around the nerves themselves, such as if a patient develops neuritis of the nerves after radiofrequency ablation/neurotomy/rhizotomy.

Contraindications

• Common contraindications

Anatomy

The knee is innervated by several genicular nerves. These nerves are articular branches formed from the femoral, saphenous, common peroneal, tibial and obturator nerves. There are several branches, but the following 3 are the ones targeted for treatment. They run along the bones, which give us fluoro targets:

• Superior lateral (SL) (along femur)
• Superior medial (SM) (along femur)
• Inferior medial (IM) (along tibia)

Equipment/Skills/Setup

Core Equipment/Disposables: See our disposables/equipment article for “core” items that are common to all procedures.

Special items and suggested setup for this procedure (see quick guide video above for example tray prep):

• 6-10cc local anesthetic as your injectate in a 10cc syringe
• 25g x 1.5″ hypodermic needle as your primary needle

Landmarks and Patient Positioning

1. Position the patient in a basic supine position.
2. Bend the operative leg to about 45 degrees or a little less and keep the contralateral leg straight. (The goal is just to keep the non-operative leg out of the way while getting a lateral view)
   1. Alternatively you could bend the non-operative leg and keep the operative leg flat.
3. Position the patient/bed so that the bottom of the c-arm can go under the table below the knee, then simply rotate for a lateral view of the knee.

Technique

1. Start with your lateral view of the knee and place a pointer right over your first target: either the lateral or medial femoral targets (SM and SL in the diagram above).
2. Then simply insert your 25g x 1.5″ hypodermic needle “down the barrel” till you contact bone.
3. Inject medication.
4. Repeat for the other side of the femur and then for the tibial target (IM in the diagram above)

Images below show all needles at all 3 targets:

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Tips

1. NEEDLE CHOICE: Usually these bones are superficial enough that you can get to it with a basic 25g x 1.5″ hypodermic needle.
   1. This way you don’t have to use a quincke needle, and since you’re just using a 25g you probably don’t need to anesthetize the skin (it’s the same needle you would use to anesthetize so instead of doing 2 pokes with the same needle, just do the one poke).
   2. Also, you probably don’t need a bent needle since you’re traveling a short distance.
   3. If it isn’t long enough simply inject 1% lidocaine while pulling the needle out and then re-insert a longer quincke needle to reach your target.

References

Procedure Related

1. Radiofrequency techniques to treat chronic knee pain: a comprehensive review of anatomy, effectiveness, treatment parameters, and patient selection
   1. Broad overview of many topics related to knee pain and RF in the pain literate.
   2. Good review of knee neuroanatomy
   3. Reviews many studies about RF for the knee and summarizes different RF modalities used in different studies along with their results.
2. 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
   1. Reviews some technique and has images for genicular block and RF.

General Clinical

1. Radiofrequency treatment relieves chronic knee osteoarthritis pain: a double-blind randomized controlled trial
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