Knee Cryoneurolysis: Procedure, Indications, Benefits, and Recovery

What is the procedure to freeze nerves in the knee?

Freezing nerves in the knee, clinically known as cryoneurolysis or cryoablation of the genicular nerves, is a minimally invasive medical procedure designed to alleviate chronic knee pain by temporarily disabling the sensory nerves responsible for transmitting pain signals from the joint.

Understanding Knee Pain and Nerve Function

Chronic knee pain often stems from conditions like osteoarthritis, previous injury, or failed surgical interventions. While the structural damage within the knee joint is the primary cause, the sensation of pain is conveyed to the brain via a network of sensory nerves. Specifically, the genicular nerves, which are branches off the tibial and common peroneal nerves, innervate the knee joint capsule and play a crucial role in pain transmission. By targeting these nerves, it's possible to interrupt the pain signals without affecting motor function, as these are primarily sensory nerves.

What is Cryoneurolysis?

Cryoneurolysis, or cryoablation, is a procedure that uses extremely cold temperatures to create a reversible lesion on a nerve. A specialized probe is inserted near the target nerve, and a controlled cooling process, typically reaching temperatures around -60°C to -80°C, forms an "ice ball" around the nerve. This cold exposure temporarily damages the myelin sheath and axon of the nerve, inhibiting its ability to transmit pain signals. The nerve structure itself remains intact, allowing for eventual regeneration and restoration of function, meaning the pain relief is temporary.

Indications for Cryoneurolysis

Cryoneurolysis is typically considered for individuals experiencing chronic knee pain who have not found adequate relief from conservative treatments such as physical therapy, oral medications, or corticosteroid injections. Common indications include:

• Osteoarthritis of the knee: Especially for those who are not candidates for knee replacement surgery or are seeking to delay it.
• Chronic post-surgical knee pain: Pain persisting after knee arthroscopy or total knee arthroplasty.
• Persistent knee pain from other degenerative conditions or injuries.
• Patients seeking a non-opioid pain management solution.

It serves as a bridge therapy, offering pain relief that can allow for improved participation in physical therapy and daily activities.

The Procedure: Step-by-Step

The cryoneurolysis procedure is performed in an outpatient setting and typically takes less than an hour.

• Preparation: The patient will lie on an examination table. The skin around the knee will be thoroughly cleaned with an antiseptic solution.
• Local Anesthesia: A local anesthetic is injected into the skin and deeper tissues around the targeted nerve sites to numb the area, ensuring patient comfort during the procedure.
• Image Guidance: To ensure precise placement of the cryoprobe and avoid damage to surrounding structures, the physician uses real-time imaging guidance, usually ultrasound or fluoroscopy (a type of X-ray).
• Cryoprobe Insertion: A thin, hollow needle (the cryoprobe) is carefully inserted through the skin and guided to the precise location of the target genicular nerve.
• Nerve Freezing: Once the probe is confirmed to be in the correct position, the cryoablation device is activated. A gas (often nitrous oxide or carbon dioxide) circulates through the probe, rapidly cooling its tip and creating an ice ball around the nerve. The freezing cycle typically lasts for several minutes, often repeated for multiple cycles to ensure effective nerve stunning.
• Probe Removal: After the freezing cycles are complete, the probe is slowly warmed and then withdrawn.
• Completion: A small bandage is applied to the insertion site.

Anatomy Targeted: Genicular Nerves

The primary targets for cryoneurolysis in the knee are the genicular nerves. These include:

• Superomedial Genicular Nerve (SMGN)
• Inferomedial Genicular Nerve (IMGN)
• Superolateral Genicular Nerve (SLGN)
• Inferolateral Genicular Nerve (ILGN)

These specific nerves are consistently located around the knee joint and are responsible for transmitting a significant portion of the pain signals. Prior to the cryoneurolysis procedure, a diagnostic nerve block may be performed. In this test, a local anesthetic is injected around the genicular nerves. If the patient experiences significant pain relief from this temporary block, it indicates that these nerves are indeed the source of their pain and that cryoneurolysis is likely to be effective.

Expected Outcomes and Recovery

Patients may experience immediate pain relief, although it can take a few days for the full effect to be noticeable as nerve function gradually diminishes. The pain relief from cryoneurolysis is temporary, typically lasting from 3 to 12 months, as the nerve regenerates.

• Immediate Post-Procedure: Some mild soreness, bruising, or swelling at the injection sites is common.
• Activity: Patients are generally advised to rest for the remainder of the day but can typically resume light activities the following day. Strenuous exercise should be avoided for a few days.
• Numbness: Temporary numbness or a tingling sensation in the area supplied by the treated nerves is expected and usually resolves over time as the nerve recovers.

Potential Benefits

• Minimally Invasive: It is a non-surgical procedure with a short recovery time.
• Reduced Pain: Offers significant pain relief, improving quality of life.
• Improved Function: Reduced pain can enable greater participation in physical therapy and daily activities.
• Non-Opioid Option: Provides an alternative to long-term opioid use for chronic pain management.
• Repeatable: The procedure can be safely repeated if pain returns after nerve regeneration.

Potential Risks and Considerations

While generally safe, cryoneurolysis carries some potential risks, though serious complications are rare:

• Temporary Numbness: The most common side effect, which usually resolves within weeks to months.
• Bruising and Swelling: At the injection site.
• Infection: A rare risk with any invasive procedure.
• Bleeding: Minor bleeding at the insertion site.
• Nerve Damage: Though rare and typically temporary, unintended damage to adjacent nerves could occur.
• Pain Recurrence: The nerve will eventually regenerate, and pain may return.

Who Performs This Procedure?

Cryoneurolysis of the genicular nerves is typically performed by specialists in pain management, interventional radiologists, or orthopedic surgeons who have specific training in image-guided procedures.

Conclusion

Cryoneurolysis offers a valuable, minimally invasive option for individuals suffering from chronic knee pain who have not responded to conservative treatments. By temporarily interrupting pain signals from the genicular nerves, it can provide significant pain relief, improve function, and enhance the overall quality of life. As with any medical procedure, a thorough consultation with a qualified healthcare professional is essential to determine if cryoneurolysis is the appropriate treatment option for your specific condition.