Etiology — what causes it

Disc herniation involves displacement of nucleus pulposus through a defect in the annulus fibrosus. Contributors include cumulative microtrauma from repetitive flexion–rotation loading, sudden axial loading, age-related disc degeneration with reduced hydration of the nucleus, genetic predisposition, and smoking (which impairs disc nutrition). The herniation can directly compress neural structures or trigger a chemical inflammatory response that irritates the nerve root.

Epidemiology — who gets it

Symptomatic lumbar disc herniations occur in about 1–2% of the population annually, with peak incidence between ages 30–50 (Jordan et al., BMJ Clin Evid). L4–L5 and L5–S1 levels account for over 90% of clinically relevant herniations. Importantly, MRI studies show that disc bulges and herniations are common in pain-free adults — over 50% of asymptomatic adults over 40 (Brinjikji et al., AJNR 2015).

Clinical signs

Positive straight leg raise (reproducing leg-dominant symptoms below 60° has highest specificity), positive crossed straight leg raise (high specificity for herniation), dermatomal sensory loss, myotomal weakness, and diminished or absent deep tendon reflexes corresponding to the involved level. Centralization with repeated movement testing (McKenzie assessment) is a positive prognostic sign.

Symptoms

Low back pain with radiating leg pain following a dermatomal pattern (sharp, burning, electric), often dominant in the leg. Pain typically worse with sitting, forward bending, sneezing, coughing, and the Valsalva maneuver. Numbness or paresthesias may follow the same dermatome. Symptoms often peak in intensity in the first 1–2 weeks.

Best evidence for chiropractic treatment

Conservative care is the recommended first-line approach for the majority of lumbar disc herniations without progressive neurological deficit (NASS guidelines; JOSPT CPGs). The SPORT trial (Weinstein et al., JAMA) showed that surgical and non-surgical outcomes converge by 1–2 years. Exercise therapy, spinal manipulation in appropriately screened patients, neural mobilization, and directional preference exercises all have supportive evidence (Hahne et al., Spine; Lewis et al., Cochrane 2015). Epidural steroid injection may provide short-term relief in selected radicular cases. Surgical referral is reserved for progressive neurological deficit, cauda equina syndrome, or persistent disabling pain after 6–12 weeks of structured conservative care.

Subtypes

  • Disc bulge. Annular fibers intact; broad-based protrusion. Often incidental and asymptomatic.
  • Protrusion. Focal extension of nucleus; annulus remains intact. May cause root irritation if positioned near a nerve.
  • Extrusion. Nucleus material breaks through the annulus but remains continuous with the disc. More likely to cause significant radicular symptoms.
  • Sequestration. Free fragment separated from the disc. Paradoxically, sequestrations often resorb spontaneously and have a good prognosis with conservative care.

When to seek emergency care

Some symptoms need urgent medical attention — not a chiropractic visit. Call 911 or go to the nearest emergency department for: progressive limb weakness, loss of bowel or bladder control, saddle anesthesia (numbness in the groin/inner thighs), severe unrelenting pain unrelieved by position, signs of fracture after significant trauma, chest pain, stroke-like symptoms (face drooping, arm weakness, speech changes), or any rapidly worsening or unusual symptom.

Bottom line

Most lumbar disc herniations improve substantially with conservative care over 6–12 weeks. Surgery is rarely the first answer. Active care, education, and graded loading do most of the work.