The Investigators have designed this exploratory study in patients suffering from zygapophysial joint mediated pain to investigate if a correlation exists between inter-individual genetic variability (genotype) with treatment response (phenotype). More specifically, the investigators aim to identify any form of correlation between a specific SNP of the BDNF gene (Val66Met) and the effectiveness and/or duration of radiofrequency facet joint neurotomy. The study population is patients suffering from chronic low back pain who have been scheduled for radiofrequency neurotomy following the diagnosis of facet joint mediated pain (using medial branch block test). The investigators will evaluate if a common variant of BDNF gene (Val66Met) can be directly correlated to a significant degree of pain relief following RF treatment, and whether the result of such a procedure can be predicted from a specific genetic profile.

Study Hypothesis It is possible to predict individual responsiveness to radiofrequency denervation for zygapophysial (facet) joint mediated pain on the basis of a specific genetic pattern (Single Nucleotide Polymorphism, [SNP])?

Inclusion Criteria:

• Diagnosed with chronic low back pain which is unresponsive to conservative treatment (including suitable analgesics and physical therapy);
• Willing to provide consent
• Subject is capable of comprehending the patient information sheet and has the capacity to give their informed consent to all study procedures in English
• Be 18 years or older at the time of enrolment;
• Have specific low back pain that is aggravated by hyperextension and rotation of the spine, with or without hip, buttock or leg pain that does not follow a known dermatomal distribution
• Paraspinal Tenderness
• A "positive" response to a uni/bi-lateral MBB* (a response is considered positive when a subject experiences at least 50% reduction in pain scores after the block, regardless of the duration of pain relief)

Exclusion Criteria:

• Patients who had had any previous back surgery
• Patients who had previous RF treatments for facet joints mediated pain
• Patients with another significant cause of low back pain (like spinal stenosis, disc herniation, spondylolisthesis, malignancy, infection or trauma);
• Radicular pain (pain with neuropathic characteristics following one or more nerve root distribution)
• Patients with bleeding complications or coagulopathy issues;
• Concurrent participation in other experimental trials;
• Known history of adverse reactions to local anesthetics;
• Pregnant or lactating women;
• Refusal to provide informed consent for blood banking
• Any other complication which in the view of the investigator may interfere with the study procedures or the measurement of the accurate study outcomes

Patients suffering from chronic and debilitating low back pain with a diagnosis of lumbar zygapophysial joint mediated pain which has not been effectively treated with conservative pharmacological treatment or alternative non-invasive treatments