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 isn’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, can then 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

Anatomy

Equipment/Skills/Setup

See our disposables/equipment article for “core” supplies that are common to all procedures. Highlights below:

  • Core Equipment
    • c-arm, c-arm compatible bed
  • Core Disposables
    • Procedure tray. As outlined in the above link, core supplies include a pointer, syringes for subcutaneous local, syringe for injectate, drape.

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 treatment 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)
  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:

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

  1. Radiofrequency techniques to treat chronic knee pain: a comprehensive review of anatomy, effectiveness, treatment parameters, and patient selection