L5-S1 Disc Protrusion (2mm Broad-Based Posterior): Meaning and Management

An L5-S1 broad-based posterior disc protrusion of 2 mm is a common MRI finding. Clinical significance depends on correlation with symptoms.

Anatomy & Terminology

• L5-S1: Lumbosacral junction; highest mechanical load.
• Broad-based: >25% (or >90°) of disc circumference involved (vs. focal <25%).
• Posterior: Toward spinal canal/nerve roots.
• Protrusion (vs. extrusion): Base wider than apex; annulus intact.
• 2 mm: Small; many asymptomatic adults have similar findings.

Potential Symptoms

• Asymptomatic: Incidental finding (common).
• Radiculopathy (S1): Pain radiating down posterior thigh/leg to lateral foot; numbness lateral foot/sole; ankle jerk diminished; weakness plantar flexion.
• Back pain: Axial mechanical pain from annular stretch/inflammation.
• Cauda equina (rare): Saddle anesthesia, bowel/bladder dysfunction — emergency.

Management (Conservative First)

1. Activity modification: Avoid prolonged sitting, heavy lifting, flexion/rotation.
2. NSAIDs: Ibuprofen/naproxen short course.
3. Physical therapy: McKenzie extension, core stabilization, nerve glides, posture.
4. Epidural steroid injection: If radiculopathy >6 weeks unresponsive.
5. Time: 80–90% improve in 6–12 weeks.

Surgical Indications

• Progressive motor deficit.
• Cauda equina syndrome.
• Intractable pain >6–12 months despite comprehensive non-op care.
• Microdiscectomy (gold standard); success >85% for leg pain.

Imaging Follow-up

Not needed unless symptoms worsen or surgery planned. Disc protrusions often resorb spontaneously.

Treat the patient, not the MRI. Many 2 mm protrusions require no intervention.