Osteoarthritis (OA) is one of the most frequent causes of chronic pain, often intense, debilitating and responsible for a large percentage of the elderly. The disease affects about 10% of adults and the knees are the most affected joints. The diagnosis of OA in the knee is predominantly clinical, and can be confirmed by radiological examination. Systemic drugs are indicated before invasive procedures, but pharmacological therapies may offer limited benefits. Thermal radiofrequency lesions of genicular nerves has been used to relieve chronic knee pain, as adjuvant therapy, but with high costs and low availability in the public system. The use of phenol for peripheral analgesic blocks has emerged as a good option and at low cost and can be used in any service of Pain Treatment. The aim of the study is to evaluate the efficacy of 6% phenol for ultrasound-guided genicular nerves neurolysis for the treatment of patients with chronic knee pain due to osteoarthritis.

METHODS: A prospective study will be carried out with 15 patients with chronic pain (more than 4 months) and diagnosis of arthrosis by imaging, with pain intensity greater than 4 (from zero to 10) that will be submitted to ultrasound-guided genicular nerves block. The test block will be performed with 0.25% -1,5 mL bupivacaine on each nerve. Patients who present pain improvement> 50% will undergo neurolysis of genicular nerves with 1,5 mL of 7% phenol in each of the genicular nerves. After the procedure, the patients will be evaluated for 3 months in relation to the intensity of pain at rest and movement and duration of analgesia provided by the intervention, range of movements and functionality of the knee joint.

Inclusion Criteria:

• Signature of the free, informed consent form
• Age over 18 years old
• Knee pain for more than six months without improvement with clinical treatment
• Clinical and imaging diagnosis (radiography) of knee osteoarthritis
• Moderate pain intensity (pain greater than 4, by the numerical scale).

Exclusion Criteria:

• Cognitive impairment or psychiatric disease
• Other causes of knee pain (trauma, complex regional pain syndrome)
• Puncture site infection
• Coagulopathy or use of anticoagulant.