Facet (zygapophyseal) joints are paired synovial joints between adjacent vertebrae that limit segmental motion and bear approximately 15-25% of axial load (more in the lumbar spine during extension). Aging, repetitive microtrauma, disc degeneration with loss of disc height, segmental instability, and inflammation lead to osteoarthritis with cartilage loss, osteophytes, capsular thickening, synovitis, and meniscoid impingement. Each facet is innervated by the medial branch of the dorsal ramus from its level and the level above.
Patients describe deep, dull, axial low back or neck pain that worsens with extension, ipsilateral side bending, and rotation; pain radiation is typically non-dermatomal and ends at or above the knee or elbow (sclerotomal). Morning stiffness improving with movement and pain after prolonged sitting are common. Examination shows paraspinal tenderness, reproduced pain with extension and rotation (Kemp test), and limited segmental motion. Imaging with X-ray, CT, and MRI shows osteoarthritic changes, but findings correlate poorly with symptoms; the gold standard for diagnosis is comparative medial branch block reducing pain >50-80%.
Treatment is multimodal. Conservative therapy includes NSAIDs, topical analgesics, paraspinal muscle strengthening, postural training, manual therapy, and weight reduction. Intra-articular facet injection with corticosteroid provides short-term relief in some patients. Diagnostic and therapeutic medial branch blocks identify candidates for radiofrequency neurotomy (RFA), which provides 6-12 months of relief in well-selected patients with positive comparative blocks. Multilevel disease, instability, or refractory cases may require surgical evaluation, including transforaminal interbody fusion if radiculopathy or instability is present, but isolated facet syndrome rarely requires fusion.