Phenol Neurolysis of Genicular Nerves for Osteoarthritic Knee Pain

As the aging and obese populations continue to increase, there is a rapidly growing number of people at risk for knee osteoarthritis. Treatment typically starts conservatively with analgesics, physical therapy, and bracing. Intra-articular injections with corticosteroids and/or viscosupplementation may also be utilized in those with persistent knee pain. Genicular nerve radiofrequency ablation (GNRFA) is an increasingly employed procedure for refractory osteoarthritic knee pain with promising efficacy for pain relief. However, due to its reliance on expensive equipment, additional staff, and need for specialized rooms (eg. fluoroscopy suite), GNRFA is a costly procedure with limited availability. Chemical neurolysis is an alternative method of nerve ablation using alcohol or phenol utilized in the management of pain. Recent literature has demonstrated good efficacy for pain relief and function with chemical ablation of the genicular nerves using both alcohol and phenol. This study is a double-blind, randomized, placebo-controlled pilot study to assess the efficacy of phenol neurolysis of the genicular nerves for pain and function due to refractory osteoarthritic knee pain. We hypothesize that a significant improvement in both pain and function will be observed with chemical neurolysis of the genicular nerves using 6% phenol compared to placebo.

1.5 mL of 6% aqueous phenol will be injected at each target genicular nerve under ultrasound guidance.

Participants' pain will be measured using the numeric rating scale (0-10) prior to the intervention and at 1 month, 3 months, and 6 months after the intervention. Numeric rating scale ranges from 0 (no pain) to 10 (worst pain).

Participants' function as measured by WOMAC will be measured prior to the intervention and at 1 month, 3 months, and 6 months after the intervention. WOMAC score ranges from 0 (best) to 100 (worst).

Inclusion Criteria: Radiographic knee osteoarthritis (Kellgren-Lawrence grade 2-4) Knee pain of moderate intensity or greater (NRS of 4 or greater) Knee pain for 3 months or longer Persistent knee pain despite conservative treatment including oral/topical analgesics, physiotherapy, intra-articular injection with corticosteroid and/or hyaluronic acid Exclusion Criteria: Prior total or partial knee arthroplasty in the knee(s) to be treated Prior radiofrequency ablation treatment in the affected knee Other rheumatological or connective tissue disease(s) affecting the knee to be treated History of bleeding disorder Any psychiatric or neurologic disease (eg. dementia, brain injury, etc.) that may preclude reliable reporting of symptoms and response to treatment Pregnancy Recent treatment with intraarticular hyaluronic acid, platelet-rich plasma, or corticosteroid injections to the affected knee in the past 3 months Skin or joint infection in the knee(s) to be treated Concomitant radicular pain