Lumbar Facet Syndrome

Low back pain arising from the lumbar zygapophyseal (facet) joints, paired synovial joints in the posterior elements innervated by the medial branches of the dorsal rami (each joint receives dual supply from the level above and below). The joints bear about 20 to 25% of axial load and more with extension and rotation.

• Causes: degenerative osteoarthritis (disc height loss increases facet load), repetitive extension and rotation (golf, tennis, gymnastics, cricket), trauma, spondylolisthesis, synovial impingement or capsular tears, inflammatory arthritis, and rarely synovial cysts.
• Facet joints are the source of pain in about 15 to 45% of patients with chronic low back pain (about 15% in younger patients and about 40% in older patients), with L4-L5 and L5-S1 most often affected.
• Natural history: often episodic with recurrence, and most patients improve with conservative care over weeks to months.

• Axial low back pain, often unilateral and paramedian, worse with extension, rotation, and standing or walking after prolonged lumbar extension, relieved by flexion and sitting, with morning stiffness, and referred pain to the buttock, hip, groin and posterior thigh (rarely to the calf or foot). Pain below the knee is unusual.
• Examination: tenderness over the facet joints (2 to 3 cm lateral to the midline), pain on extension with rotation (Kemp test, limited sensitivity), reduced extension, normal neurological examination and negative straight leg raise.
• No single sign or imaging finding is diagnostic, and clinical criteria alone do not predict response to blocks.
• Differential diagnosis: discogenic pain, sacroiliac joint dysfunction, myofascial pain, spondylolysis and spondylolisthesis, radiculopathy, stenosis, hip osteoarthritis, piriformis syndrome, spondyloarthritis, vertebral fracture, infection and tumour.
• Red flags: those of any back pain (cauda equina features, progressive weakness, fever, weight loss, cancer history, trauma, night pain).
• Complications: chronic pain, reduced activity and disability, progression of degenerative disease and secondary stenosis, and synovial cyst compression of a nerve root.

• Clinical diagnosis of exclusion after neurological, hip and sacroiliac examination.
• X-ray (and oblique views) shows facet hypertrophy and joint space narrowing. CT or MRI shows facet arthropathy, effusion, synovial cysts and associated disc disease, but findings correlate poorly with pain.
• Controlled diagnostic medial branch blocks are the best confirmation: under imaging guidance, bupivacaine 0.5% 0.5 mL (or lidocaine 2% 0.5 mL) is injected at each nerve to be treated, with 80% or more pain relief for the expected duration (a second confirmatory block on a separate occasion with a different duration anaesthetic is preferred). A false positive rate of about 25 to 40% for a single block.
• Bloods (CRP, ESR, HLA-B27) when inflammatory disease is suspected.

• Conservative treatment, first line for 6 to 12 weeks: education, staying active, avoiding sustained extension and rotation loads, flexion biased and core stabilisation exercises, hip flexor and hamstring stretching, posture and ergonomic correction, weight loss, and heat.
• Analgesia: paracetamol 1 g orally 6 hourly. Naproxen 500 mg 12 hourly (or ibuprofen 400 mg 8 hourly, or diclofenac 50 mg 8 hourly) with food for 1 to 2 weeks, with gastroprotection where needed. Topical diclofenac 1% gel. Short course muscle relaxant for spasm (tizanidine 2 mg 8 hourly, or cyclobenzaprine 5 to 10 mg at night, 5 to 7 days). Duloxetine 30 to 60 mg daily for chronic pain.
• Intra articular facet steroid injection (triamcinolone 20 to 40 mg or methylprednisolone 20 to 40 mg with local anaesthetic, total volume 1 to 1.5 mL per joint under fluoroscopic or CT guidance): short term relief for some, with limited evidence for long term benefit.
• Radiofrequency ablation (denervation) of the medial branches after two positive diagnostic blocks: conventional thermal ablation at 80 to 90 degrees Celsius for 60 to 90 seconds (or cooled and pulsed techniques), with relief of 50% or more in about 50 to 70% of selected patients for 6 to 12 months (the nerve regrows, and the treatment can be repeated every 6 to 12 months). Complications: post-procedure neuritis, numbness, burns and infection.
• Surgery is seldom indicated for facet pain alone. Fusion is considered only with instability or spondylolisthesis.
• Treat synovial cysts: observation, imaging guided cyst aspiration and steroid injection, or surgical excision for neurological deficit.
• Special groups:
  • Elderly: avoid prolonged NSAIDs and cyclobenzaprine, and prefer topical agents and exercise.
  • Diabetes: monitor glucose after steroid injection (3 to 5 days).
  • Pregnancy: physiotherapy, support belts and paracetamol. Avoid NSAIDs after 20 weeks, and avoid fluoroscopy.
  • Anticoagulation: hold under specialist guidance for procedures.
  • Renal impairment and gastrointestinal disease: avoid oral NSAIDs.
• Follow up: review at 4 to 6 weeks and 3 months. Refer to pain medicine for persistent pain beyond 3 months, consideration of diagnostic blocks and radiofrequency ablation, or to spinal surgery for instability.