The term sciatica describes a characteristic pain felt in the lower back, buttocks and the posterior and lower leg. It results from compression of any of the 5 nerve roots that contribute to the sciatic nerves (L4-S3).

Most commonly affected disc - L5/S1 (S1 nerve root compressed)

Second most common - L4/L5 (L5 compressed)

The main causes of sciatica are lumbosacral nerve root compression by:

• Herniated disc
• Spondylolisthesis (anterior displacement of a vertebra out of line with the one below)
• Spinal stenosis
• Piriformis syndrome

PC

Sciatica causes unilateral pain from the buttock radiating down the back of the thigh to below the knee or feet. It might be described as an “electric” or “shooting” pain. Other symptoms:

• Altered sensation (parasthesia)
• Motor weakness
• Altered reflexes

Localised Sx:

• L5/S1 disc – S1 nerve root – will cause symptoms from the buttocks to the foot, and particularly on the lateral side of the foot. There will be calf weakness, and altered ankle reflexes.
• L4/L5 disc – L5 nerve root – pain radiating to the ankle and top of the foot sensory changes on the lateral side of the leg, and on top of the big toe.
  • Both the above will result in a positive sciatic stretch test

Bilateral sciatica is a red flag for cauda equina syndrome.