- Nerve root irritation, most commonly from herniated disc, osteophyte, other manifestation of arthritic changes
- Less common: cancer, infection, other
- Waxes/wanes, typically radiates down one leg below knee
- Vast majority affect L5 or S1 roots
- Typically pain w/o weakness or deficits unless severe compression
- More common to have pain without frank sensory or motor deficits
- If disc related root irritation: straight leg raise sensitive, crossed leg raise specific
- L5 pain/numbness top of foot; weakness in extension of toe, foot inversion
- S1: pain/numbness lateral foot; weakness in plantar flexion; diminished achilles reflex