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Sciatica (Sciatic Nerve Pain)

The sciatic nerve is the largest nerve in the human body, running from the lower back down the back of the leg into the foot. Sciatica is pain that radiates along this nerve's pathway — but the actual problem is often located far from where the pain is felt.

Anatomy​

  • The sciatic nerve forms from five spinal nerve roots — L4, L5, S1, S2, S3 — which converge before passing underneath the piriformis muscle in the gluteal region.
  • It travels down the posterior (back) side of the thigh, then splits into two branches: the tibial nerve (continues down the back of the lower leg to the bottom of the foot) and the common fibular nerve (moves to the front of the lower leg and top of the foot).
  • In some people, part of the nerve (commonly the common fibular component) pierces directly through the piriformis muscle instead of passing underneath it, which can make that portion more susceptible to irritation/compression.

Why Sciatica Often Starts in the Lower Back​

  • Between vertebral bodies sit intervertebral discs, each with a tough outer ring (annulus fibrosus) and a soft, gelatinous center (nucleus pulposus).
  • A disc can herniate/bulge suddenly (e.g., lifting heavy while bending/twisting tears the annulus fibrosus) or gradually (discs lose water content and structural integrity with age).
  • Posterior-lateral herniations (most common) tend to miss the nerve root exiting at that same disc level and instead compress the nerve root passing behind it that is headed to the level below — e.g., an L4-L5 disc herniation typically misses the L4 nerve and compresses the L5 nerve root. This is also why an L5-S1 herniation can cause S1 symptoms even though there's no disc between S1 and S2.
  • Far-lateral herniations (less common) bulge further to the side and can instead compress the nerve root exiting at that same level (e.g., the L4 nerve at an L4-L5 disc).
  • A large enough herniation can compress more than one nerve root at once.
  • Discs are avascular (no direct blood supply, relying on diffusion from surrounding tissue), so they heal slower than well-vascularized tissue — though the body can gradually resorb herniated disc material over time, reducing nerve irritation.

Piriformis Syndrome / Deep Gluteal Syndrome​

Sciatic nerve irritation can also occur outside the spine, in the gluteal region where the nerve passes underneath (or through) the piriformis muscle. This is called piriformis syndrome, though some clinicians prefer the broader term deep gluteal syndrome since other structures in the region can also irritate the nerve.

Diagnosis: Dermatomes and Myotomes​

  • A dermatome is a skin area whose sensory innervation comes primarily from one spinal nerve level — compressing a nerve root causes pain/numbness/tingling along its dermatome (e.g., L5 vs. S1 dermatomes differ), which helps localize the affected level.
  • A myotome is a muscle group whose motor innervation comes primarily from one spinal nerve root — compression can cause weakness in that myotome's muscles, tested via movements specific to that spinal level.
  • Since spinal nerves carry both sensory and motor fibers, clinicians use dermatome/myotome testing to narrow down the likely nerve root, then confirm with imaging (MRI) to check for a bulging/herniated disc.

Treatment (Usually Starts Conservative)​

For disc-related sciatica:

  1. Avoid movements/activities that significantly aggravate symptoms (if acute), while maintaining activity as tolerated; over-the-counter pain medication as needed.
  2. Strengthen the core (obliques, transversus abdominis, spinal extensors) to improve spinal stability and reduce future risk — self-directed or with a physical therapist for stubborn cases.
  3. Weight loss if carrying excess body weight, to reduce mechanical loading on the lumbar spine.
  4. If not improving: steroid injections to reduce inflammation around the irritated nerve root (has pros/cons); newer options like platelet-rich plasma (PRP) injections are still being studied.
  5. Surgery if symptoms persist or there's significant neurological involvement — e.g., trimming the herniated disc portion compressing the nerve, or removing bone to create more space around the nerve root.

For piriformis/deep gluteal syndrome (problem originates at the hip, not the spine):

  • Stretching the piriformis/deep gluteal muscles (e.g., figure-four stretch, half pigeon stretch), as long as they don't aggravate symptoms.
  • Strengthening hip muscles: bridges, clamshells, resisted hip abduction.
  • Sciatic nerve glides (via a physical therapist): specific movements to gently mobilize the nerve relative to surrounding tissue.

Key Takeaway​

Proper lifting mechanics, core strengthening, and maintaining spinal/hip range of motion reduce both flare-up risk and the risk of developing sciatica in the first place. Injections and surgery are reserved for cases where conservative treatment isn't enough.